| |
Main
Date: 28 Oct 2007 10:48:03
From:
Subject: Mount front brakes on rear?
|
Nashbar has a good deal on ultegra brake calipers; I mounted them on
my front wheel. My rear caliper is kinda corroded, and I was
considering mounting another front caliper on the rear wheel... Is
this a good idea?
|
|
| |
Date: 05 Nov 2007 08:24:32
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 4, 12:23 pm, jim beam <spamvor...@bad.example.net > wrote:
> unforgive...@juno.com wrote:
> > On Nov 3, 7:27 pm, jim beam <spamvor...@bad.example.net> wrote:
> >> unforgive...@juno.com wrote:
> >>> On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net> wrote:
> >>>> unforgive...@juno.com wrote:
> >>>>> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
> >>>>>> _ wrote:
> >>>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
> >>>>>>>>>> What should I be measuring?
> >>>>>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
> >>>>>>>>> distance between the front tips of the brake pads with the caliper
> >>>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
> >>>>>>>>> open, the front tips are further apart than the rears. when closed,
> >>>>>>>>> the front tips are closer than the rears. [front caliper]
> >>>>>>>> I'm using the moulding seam of the brake block at the point it touches the
> >>>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> >>>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
> >>>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> >>>>>>>> I can't detect any sign of the effect you say is there.
> >>>>>>>> James Thomson
> >>>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
> >>>>>>> was already pointed out.
> >>>>>> no, these are new calipers - in perfect condition.
> >>>>>>> It's impossible for an arm to pivot on a
> >>>>>>> cylindrical bushing and change the axis of rotation without another pivot
> >>>>>>> (which is, in essemce, what beamboy is claiming).
> >>>>>> no it's not. it's a simple geometry problem. you not figuring it out
> >>>>>> doesn't mean it's impossible - after all, it is observed to be happening.
> >>>>> Yes, it's a very simple geometry problem. Far simpler than your
> >>>>> explanation of magic pivots describes. The brake pads are adjustable
> >>>>> in a number of directions, one of which is rotation about the pad
> >>>>> fixing bolt.
> >>>> duh. and when that bolt is tightened, they remain fixed. from that
> >>>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
> >>>> did, remain the same.
> >>>>> Look at the brake from the side with the mounting bolt
> >>>>> horizontal, and if the brake is set up to go on the rear, the rear
> >>>>> ends of the pads are going to be sitting lower than the front ends.
> >>>>> Assuming everything is set up square and parallel when the pads are
> >>>>> about a rim width apart, this will will give the appearance of the
> >>>>> front ends of the pads pointing inwards when you open the caliper all
> >>>>> the way. The rear ends of the pads moved farther out horizontally
> >>>>> because they are father from the pivot axes. Close the caliper all
> >>>>> the way and the front ends of the pads will be pointed out, because
> >>>>> they traveled a shorter horizontal distance for the same angle. Re-
> >>>>> adjust the pads so that the front ends are sitting lower than the rear
> >>>>> when viewed from the side, and you get the exact opposite behavior.
> >>>>> Adjust them level, and you're back to boring old parallel motion,
> >>>>> which is what everyone who actually wasted their time obeying your
> >>>>> command to measure their brakes observed. This is why you need to
> >>>>> prove your magic pivot theory by measuring from the arms not the
> >>>>> pads. The pads may be fixed, but they are not always fixed in a
> >>>>> position that supports your theory. If the second pivot really is
> >>>>> angled, there will also be some fore-aft translation of the arm
> >>>>> attached to it. Another reason why common sense dictates that this
> >>>>> would be an incredibly stupid way to design a brake.
> >>>> says the guy that doesn't understand the concepts.
> >>> And what concepts would those be? That the distance traveled by a
> >>> point on a rigid rotating body does not depend on that point's
> >>> distance from the axis of rotation? Because that's what you're trying
> >>> to claim, and you're exactly right that I don't understand it. You
> >>> would be hard pressed to find anyone with a passing knowledge of
> >>> geometry who would buy that one. If you change the relative distances
> >>> of the pad ends from the pivot axes (in whichever direction you
> >>> believe them to be pointing) the delta measurements you performed will
> >>> change. Front or rear, and I'm looking at it right now on a single
> >>> pivot caliper.
> >> eh? you're basing your entire comment on single pivot???? holy carp.
>
> >>> The ends of the pads farthest from the pivot will
> >>> always be farther apart when the caliper is open, and closer together
> >>> when it's closed. How do you suppose it is that I can observe
> >>> something that you say absolutely has to be the result of one of a two
> >>> degree of freedom mechanism on a brake with only one degree of freedom?
> >> forget it. if you can't be bothered, nor can i.
>
> > No, I'm basing it on single pivot, dual pivot, and common sense.
>
> no, you're basing it on single pivot and underinformed presumption.
>
> > And
> > if your observation of changing brake pad distances can be observed in
> > a single pivot brake, then it absolutely cannot be proof of out of
> > plane rotation.
>
> rubbish.
Please tell me what it is that I'm presuming. I've duplicated your
progressive toe in measurements on both single and dual pivot brakes,
and I've changed it to a progressive toe out simply by changing the
pad adjustment. If either of those calipers has an arm that's
rotating out of plane, brake pad measurements simply are not
sufficient proof. Seeing how you're the only person on the planet
that believes that this rotation is happening, you're going to have to
do a lot more than stomp your feet and yell rubbish to convince me.
|
| | |
Date: 06 Nov 2007 20:32:57
From: jim beam
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
> On Nov 4, 12:23 pm, jim beam <spamvor...@bad.example.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Nov 3, 7:27 pm, jim beam <spamvor...@bad.example.net> wrote:
>>>> unforgive...@juno.com wrote:
>>>>> On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net> wrote:
>>>>>> unforgive...@juno.com wrote:
>>>>>>> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
>>>>>>>> _ wrote:
>>>>>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
>>>>>>>>>>>> What should I be measuring?
>>>>>>>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
>>>>>>>>>>> distance between the front tips of the brake pads with the caliper
>>>>>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
>>>>>>>>>>> open, the front tips are further apart than the rears. when closed,
>>>>>>>>>>> the front tips are closer than the rears. [front caliper]
>>>>>>>>>> I'm using the moulding seam of the brake block at the point it touches the
>>>>>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
>>>>>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
>>>>>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
>>>>>>>>>> I can't detect any sign of the effect you say is there.
>>>>>>>>>> James Thomson
>>>>>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
>>>>>>>>> was already pointed out.
>>>>>>>> no, these are new calipers - in perfect condition.
>>>>>>>>> It's impossible for an arm to pivot on a
>>>>>>>>> cylindrical bushing and change the axis of rotation without another pivot
>>>>>>>>> (which is, in essemce, what beamboy is claiming).
>>>>>>>> no it's not. it's a simple geometry problem. you not figuring it out
>>>>>>>> doesn't mean it's impossible - after all, it is observed to be happening.
>>>>>>> Yes, it's a very simple geometry problem. Far simpler than your
>>>>>>> explanation of magic pivots describes. The brake pads are adjustable
>>>>>>> in a number of directions, one of which is rotation about the pad
>>>>>>> fixing bolt.
>>>>>> duh. and when that bolt is tightened, they remain fixed. from that
>>>>>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
>>>>>> did, remain the same.
>>>>>>> Look at the brake from the side with the mounting bolt
>>>>>>> horizontal, and if the brake is set up to go on the rear, the rear
>>>>>>> ends of the pads are going to be sitting lower than the front ends.
>>>>>>> Assuming everything is set up square and parallel when the pads are
>>>>>>> about a rim width apart, this will will give the appearance of the
>>>>>>> front ends of the pads pointing inwards when you open the caliper all
>>>>>>> the way. The rear ends of the pads moved farther out horizontally
>>>>>>> because they are father from the pivot axes. Close the caliper all
>>>>>>> the way and the front ends of the pads will be pointed out, because
>>>>>>> they traveled a shorter horizontal distance for the same angle. Re-
>>>>>>> adjust the pads so that the front ends are sitting lower than the rear
>>>>>>> when viewed from the side, and you get the exact opposite behavior.
>>>>>>> Adjust them level, and you're back to boring old parallel motion,
>>>>>>> which is what everyone who actually wasted their time obeying your
>>>>>>> command to measure their brakes observed. This is why you need to
>>>>>>> prove your magic pivot theory by measuring from the arms not the
>>>>>>> pads. The pads may be fixed, but they are not always fixed in a
>>>>>>> position that supports your theory. If the second pivot really is
>>>>>>> angled, there will also be some fore-aft translation of the arm
>>>>>>> attached to it. Another reason why common sense dictates that this
>>>>>>> would be an incredibly stupid way to design a brake.
>>>>>> says the guy that doesn't understand the concepts.
>>>>> And what concepts would those be? That the distance traveled by a
>>>>> point on a rigid rotating body does not depend on that point's
>>>>> distance from the axis of rotation? Because that's what you're trying
>>>>> to claim, and you're exactly right that I don't understand it. You
>>>>> would be hard pressed to find anyone with a passing knowledge of
>>>>> geometry who would buy that one. If you change the relative distances
>>>>> of the pad ends from the pivot axes (in whichever direction you
>>>>> believe them to be pointing) the delta measurements you performed will
>>>>> change. Front or rear, and I'm looking at it right now on a single
>>>>> pivot caliper.
>>>> eh? you're basing your entire comment on single pivot???? holy carp.
>>>>> The ends of the pads farthest from the pivot will
>>>>> always be farther apart when the caliper is open, and closer together
>>>>> when it's closed. How do you suppose it is that I can observe
>>>>> something that you say absolutely has to be the result of one of a two
>>>>> degree of freedom mechanism on a brake with only one degree of freedom?
>>>> forget it. if you can't be bothered, nor can i.
>>> No, I'm basing it on single pivot, dual pivot, and common sense.
>> no, you're basing it on single pivot and underinformed presumption.
>>
>>> And
>>> if your observation of changing brake pad distances can be observed in
>>> a single pivot brake, then it absolutely cannot be proof of out of
>>> plane rotation.
>> rubbish.
>
> Please tell me what it is that I'm presuming. I've duplicated your
> progressive toe in measurements on both single and dual pivot brakes,
> and I've changed it to a progressive toe out simply by changing the
> pad adjustment. If either of those calipers has an arm that's
> rotating out of plane, brake pad measurements simply are not
> sufficient proof. Seeing how you're the only person on the planet
> that believes that this rotation is happening, you're going to have to
> do a lot more than stomp your feet and yell rubbish to convince me.
>
i'm not trying to "convince" you - i simply want you to stop confusing
yourself with irrelevancies about single pivot and pad adjustments [as
long as they remain fixed, the deltas remain the same] and focus on
observation of the dual pivot lever action! and even then, the ones i
have stated. it may indeed be the case that some brakes don't have this
feature, but as i have observed, campy veloce and record, and 7700
dura-ace, these definitely do!
|
| |
Date: 04 Nov 2007 09:13:09
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 3, 7:27 pm, jim beam <spamvor...@bad.example.net > wrote:
> unforgive...@juno.com wrote:
> > On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net> wrote:
> >> unforgive...@juno.com wrote:
> >>> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
> >>>> _ wrote:
> >>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
> >>>>>>>> What should I be measuring?
> >>>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
> >>>>>>> distance between the front tips of the brake pads with the caliper
> >>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
> >>>>>>> open, the front tips are further apart than the rears. when closed,
> >>>>>>> the front tips are closer than the rears. [front caliper]
> >>>>>> I'm using the moulding seam of the brake block at the point it touches the
> >>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> >>>>>> of a convenient moulding mark) trying to pick a consistent point on the
> >>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> >>>>>> I can't detect any sign of the effect you say is there.
> >>>>>> James Thomson
> >>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
> >>>>> was already pointed out.
> >>>> no, these are new calipers - in perfect condition.
> >>>>> It's impossible for an arm to pivot on a
> >>>>> cylindrical bushing and change the axis of rotation without another pivot
> >>>>> (which is, in essemce, what beamboy is claiming).
> >>>> no it's not. it's a simple geometry problem. you not figuring it out
> >>>> doesn't mean it's impossible - after all, it is observed to be happening.
> >>> Yes, it's a very simple geometry problem. Far simpler than your
> >>> explanation of magic pivots describes. The brake pads are adjustable
> >>> in a number of directions, one of which is rotation about the pad
> >>> fixing bolt.
> >> duh. and when that bolt is tightened, they remain fixed. from that
> >> point on, it doesn't matter /what/ you do, the /delta/ measurements i
> >> did, remain the same.
>
> >>> Look at the brake from the side with the mounting bolt
> >>> horizontal, and if the brake is set up to go on the rear, the rear
> >>> ends of the pads are going to be sitting lower than the front ends.
> >>> Assuming everything is set up square and parallel when the pads are
> >>> about a rim width apart, this will will give the appearance of the
> >>> front ends of the pads pointing inwards when you open the caliper all
> >>> the way. The rear ends of the pads moved farther out horizontally
> >>> because they are father from the pivot axes. Close the caliper all
> >>> the way and the front ends of the pads will be pointed out, because
> >>> they traveled a shorter horizontal distance for the same angle. Re-
> >>> adjust the pads so that the front ends are sitting lower than the rear
> >>> when viewed from the side, and you get the exact opposite behavior.
> >>> Adjust them level, and you're back to boring old parallel motion,
> >>> which is what everyone who actually wasted their time obeying your
> >>> command to measure their brakes observed. This is why you need to
> >>> prove your magic pivot theory by measuring from the arms not the
> >>> pads. The pads may be fixed, but they are not always fixed in a
> >>> position that supports your theory. If the second pivot really is
> >>> angled, there will also be some fore-aft translation of the arm
> >>> attached to it. Another reason why common sense dictates that this
> >>> would be an incredibly stupid way to design a brake.
> >> says the guy that doesn't understand the concepts.
>
> > And what concepts would those be? That the distance traveled by a
> > point on a rigid rotating body does not depend on that point's
> > distance from the axis of rotation? Because that's what you're trying
> > to claim, and you're exactly right that I don't understand it. You
> > would be hard pressed to find anyone with a passing knowledge of
> > geometry who would buy that one. If you change the relative distances
> > of the pad ends from the pivot axes (in whichever direction you
> > believe them to be pointing) the delta measurements you performed will
> > change. Front or rear, and I'm looking at it right now on a single
> > pivot caliper.
>
> eh? you're basing your entire comment on single pivot???? holy carp.
>
> > The ends of the pads farthest from the pivot will
> > always be farther apart when the caliper is open, and closer together
> > when it's closed. How do you suppose it is that I can observe
> > something that you say absolutely has to be the result of one of a two
> > degree of freedom mechanism on a brake with only one degree of freedom?
>
> forget it. if you can't be bothered, nor can i.
No, I'm basing it on single pivot, dual pivot, and common sense. And
if your observation of changing brake pad distances can be observed in
a single pivot brake, then it absolutely cannot be proof of out of
plane rotation.
|
| | |
Date: 04 Nov 2007 09:23:36
From: jim beam
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
> On Nov 3, 7:27 pm, jim beam <spamvor...@bad.example.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net> wrote:
>>>> unforgive...@juno.com wrote:
>>>>> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
>>>>>> _ wrote:
>>>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
>>>>>>>>>> What should I be measuring?
>>>>>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
>>>>>>>>> distance between the front tips of the brake pads with the caliper
>>>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
>>>>>>>>> open, the front tips are further apart than the rears. when closed,
>>>>>>>>> the front tips are closer than the rears. [front caliper]
>>>>>>>> I'm using the moulding seam of the brake block at the point it touches the
>>>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
>>>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
>>>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
>>>>>>>> I can't detect any sign of the effect you say is there.
>>>>>>>> James Thomson
>>>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
>>>>>>> was already pointed out.
>>>>>> no, these are new calipers - in perfect condition.
>>>>>>> It's impossible for an arm to pivot on a
>>>>>>> cylindrical bushing and change the axis of rotation without another pivot
>>>>>>> (which is, in essemce, what beamboy is claiming).
>>>>>> no it's not. it's a simple geometry problem. you not figuring it out
>>>>>> doesn't mean it's impossible - after all, it is observed to be happening.
>>>>> Yes, it's a very simple geometry problem. Far simpler than your
>>>>> explanation of magic pivots describes. The brake pads are adjustable
>>>>> in a number of directions, one of which is rotation about the pad
>>>>> fixing bolt.
>>>> duh. and when that bolt is tightened, they remain fixed. from that
>>>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
>>>> did, remain the same.
>>>>> Look at the brake from the side with the mounting bolt
>>>>> horizontal, and if the brake is set up to go on the rear, the rear
>>>>> ends of the pads are going to be sitting lower than the front ends.
>>>>> Assuming everything is set up square and parallel when the pads are
>>>>> about a rim width apart, this will will give the appearance of the
>>>>> front ends of the pads pointing inwards when you open the caliper all
>>>>> the way. The rear ends of the pads moved farther out horizontally
>>>>> because they are father from the pivot axes. Close the caliper all
>>>>> the way and the front ends of the pads will be pointed out, because
>>>>> they traveled a shorter horizontal distance for the same angle. Re-
>>>>> adjust the pads so that the front ends are sitting lower than the rear
>>>>> when viewed from the side, and you get the exact opposite behavior.
>>>>> Adjust them level, and you're back to boring old parallel motion,
>>>>> which is what everyone who actually wasted their time obeying your
>>>>> command to measure their brakes observed. This is why you need to
>>>>> prove your magic pivot theory by measuring from the arms not the
>>>>> pads. The pads may be fixed, but they are not always fixed in a
>>>>> position that supports your theory. If the second pivot really is
>>>>> angled, there will also be some fore-aft translation of the arm
>>>>> attached to it. Another reason why common sense dictates that this
>>>>> would be an incredibly stupid way to design a brake.
>>>> says the guy that doesn't understand the concepts.
>>> And what concepts would those be? That the distance traveled by a
>>> point on a rigid rotating body does not depend on that point's
>>> distance from the axis of rotation? Because that's what you're trying
>>> to claim, and you're exactly right that I don't understand it. You
>>> would be hard pressed to find anyone with a passing knowledge of
>>> geometry who would buy that one. If you change the relative distances
>>> of the pad ends from the pivot axes (in whichever direction you
>>> believe them to be pointing) the delta measurements you performed will
>>> change. Front or rear, and I'm looking at it right now on a single
>>> pivot caliper.
>> eh? you're basing your entire comment on single pivot???? holy carp.
>>
>>> The ends of the pads farthest from the pivot will
>>> always be farther apart when the caliper is open, and closer together
>>> when it's closed. How do you suppose it is that I can observe
>>> something that you say absolutely has to be the result of one of a two
>>> degree of freedom mechanism on a brake with only one degree of freedom?
>> forget it. if you can't be bothered, nor can i.
>
> No, I'm basing it on single pivot, dual pivot, and common sense.
no, you're basing it on single pivot and underinformed presumption.
> And
> if your observation of changing brake pad distances can be observed in
> a single pivot brake, then it absolutely cannot be proof of out of
> plane rotation.
rubbish.
|
| |
Date: 03 Nov 2007 13:17:26
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net > wrote:
> unforgive...@juno.com wrote:
> > On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
> >> _ wrote:
> >>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
> >>>>>> What should I be measuring?
> >>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
> >>>>> distance between the front tips of the brake pads with the caliper
> >>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
> >>>>> open, the front tips are further apart than the rears. when closed,
> >>>>> the front tips are closer than the rears. [front caliper]
> >>>> I'm using the moulding seam of the brake block at the point it touches the
> >>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> >>>> of a convenient moulding mark) trying to pick a consistent point on the
> >>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> >>>> I can't detect any sign of the effect you say is there.
> >>>> James Thomson
> >>> Either beam's bushings are worn or the arms are loose on the pivots - that
> >>> was already pointed out.
> >> no, these are new calipers - in perfect condition.
>
> >>> It's impossible for an arm to pivot on a
> >>> cylindrical bushing and change the axis of rotation without another pivot
> >>> (which is, in essemce, what beamboy is claiming).
> >> no it's not. it's a simple geometry problem. you not figuring it out
> >> doesn't mean it's impossible - after all, it is observed to be happening.
>
> > Yes, it's a very simple geometry problem. Far simpler than your
> > explanation of magic pivots describes. The brake pads are adjustable
> > in a number of directions, one of which is rotation about the pad
> > fixing bolt.
>
> duh. and when that bolt is tightened, they remain fixed. from that
> point on, it doesn't matter /what/ you do, the /delta/ measurements i
> did, remain the same.
>
>
>
> > Look at the brake from the side with the mounting bolt
> > horizontal, and if the brake is set up to go on the rear, the rear
> > ends of the pads are going to be sitting lower than the front ends.
> > Assuming everything is set up square and parallel when the pads are
> > about a rim width apart, this will will give the appearance of the
> > front ends of the pads pointing inwards when you open the caliper all
> > the way. The rear ends of the pads moved farther out horizontally
> > because they are father from the pivot axes. Close the caliper all
> > the way and the front ends of the pads will be pointed out, because
> > they traveled a shorter horizontal distance for the same angle. Re-
> > adjust the pads so that the front ends are sitting lower than the rear
> > when viewed from the side, and you get the exact opposite behavior.
> > Adjust them level, and you're back to boring old parallel motion,
> > which is what everyone who actually wasted their time obeying your
> > command to measure their brakes observed. This is why you need to
> > prove your magic pivot theory by measuring from the arms not the
> > pads. The pads may be fixed, but they are not always fixed in a
> > position that supports your theory. If the second pivot really is
> > angled, there will also be some fore-aft translation of the arm
> > attached to it. Another reason why common sense dictates that this
> > would be an incredibly stupid way to design a brake.
>
> says the guy that doesn't understand the concepts.
And what concepts would those be? That the distance traveled by a
point on a rigid rotating body does not depend on that point's
distance from the axis of rotation? Because that's what you're trying
to claim, and you're exactly right that I don't understand it. You
would be hard pressed to find anyone with a passing knowledge of
geometry who would buy that one. If you change the relative distances
of the pad ends from the pivot axes (in whichever direction you
believe them to be pointing) the delta measurements you performed will
change. Front or rear, and I'm looking at it right now on a single
pivot caliper. The ends of the pads farthest from the pivot will
always be farther apart when the caliper is open, and closer together
when it's closed. How do you suppose it is that I can observe
something that you say absolutely has to be the result of one of a two
degree of freedom mechanism on a brake with only one degree of freedom?
|
| | |
Date: 03 Nov 2007 17:27:14
From: jim beam
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
> On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
>>>> _ wrote:
>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
>>>>>>>> What should I be measuring?
>>>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
>>>>>>> distance between the front tips of the brake pads with the caliper
>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
>>>>>>> open, the front tips are further apart than the rears. when closed,
>>>>>>> the front tips are closer than the rears. [front caliper]
>>>>>> I'm using the moulding seam of the brake block at the point it touches the
>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
>>>>>> I can't detect any sign of the effect you say is there.
>>>>>> James Thomson
>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
>>>>> was already pointed out.
>>>> no, these are new calipers - in perfect condition.
>>>>> It's impossible for an arm to pivot on a
>>>>> cylindrical bushing and change the axis of rotation without another pivot
>>>>> (which is, in essemce, what beamboy is claiming).
>>>> no it's not. it's a simple geometry problem. you not figuring it out
>>>> doesn't mean it's impossible - after all, it is observed to be happening.
>>> Yes, it's a very simple geometry problem. Far simpler than your
>>> explanation of magic pivots describes. The brake pads are adjustable
>>> in a number of directions, one of which is rotation about the pad
>>> fixing bolt.
>> duh. and when that bolt is tightened, they remain fixed. from that
>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
>> did, remain the same.
>>
>>
>>
>>> Look at the brake from the side with the mounting bolt
>>> horizontal, and if the brake is set up to go on the rear, the rear
>>> ends of the pads are going to be sitting lower than the front ends.
>>> Assuming everything is set up square and parallel when the pads are
>>> about a rim width apart, this will will give the appearance of the
>>> front ends of the pads pointing inwards when you open the caliper all
>>> the way. The rear ends of the pads moved farther out horizontally
>>> because they are father from the pivot axes. Close the caliper all
>>> the way and the front ends of the pads will be pointed out, because
>>> they traveled a shorter horizontal distance for the same angle. Re-
>>> adjust the pads so that the front ends are sitting lower than the rear
>>> when viewed from the side, and you get the exact opposite behavior.
>>> Adjust them level, and you're back to boring old parallel motion,
>>> which is what everyone who actually wasted their time obeying your
>>> command to measure their brakes observed. This is why you need to
>>> prove your magic pivot theory by measuring from the arms not the
>>> pads. The pads may be fixed, but they are not always fixed in a
>>> position that supports your theory. If the second pivot really is
>>> angled, there will also be some fore-aft translation of the arm
>>> attached to it. Another reason why common sense dictates that this
>>> would be an incredibly stupid way to design a brake.
>> says the guy that doesn't understand the concepts.
>
> And what concepts would those be? That the distance traveled by a
> point on a rigid rotating body does not depend on that point's
> distance from the axis of rotation? Because that's what you're trying
> to claim, and you're exactly right that I don't understand it. You
> would be hard pressed to find anyone with a passing knowledge of
> geometry who would buy that one. If you change the relative distances
> of the pad ends from the pivot axes (in whichever direction you
> believe them to be pointing) the delta measurements you performed will
> change. Front or rear, and I'm looking at it right now on a single
> pivot caliper.
eh? you're basing your entire comment on single pivot???? holy carp.
> The ends of the pads farthest from the pivot will
> always be farther apart when the caliper is open, and closer together
> when it's closed. How do you suppose it is that I can observe
> something that you say absolutely has to be the result of one of a two
> degree of freedom mechanism on a brake with only one degree of freedom?
forget it. if you can't be bothered, nor can i.
|
| |
Date: 02 Nov 2007 12:58:03
From:
Subject: Re: Mount front brakes on rear?
|
All fixed! Got my new caliper in the mail. I was going to use the
washer/nut idea, but when I put the caliper through the hole in the
seatstay it was too short- only about 3 threads stuck out the other
side, and with a washer would have made matters worse.
I then considered either cutting more threads onto the bolt and
shortening it or changing it out with the one from the no-name caliper
I took off.
I was worried about tapping the bolt, as the existing threads looked
like they were formed on, and the unthreaded part of the bolt looked
like it might be too thick to cut threads into (?). I also worried
that if it didn't work, I'd have ruined the whole caliper.
So I dissassembled the old caliper. The bolt involved is actually
kinda complex, it goes from one size thread to a smaller about 1/3 of
the way along. I worried that the no-name bolt might not work on the
shimano, but to my surprise it worked just fine.
Other than pinching my palm with the spring as I dissassembled the old
caliper, it went fine.
I adjusted the pads after installation, and I cant percieve any
problem with toe in/out.
Thank you everyone for the help. Sweet!
|
| |
Date: 02 Nov 2007 08:22:07
From: Ozark Bicycle
Subject: Re: Mount front brakes on rear?
|
On Nov 2, 8:18 am, jim beam <spamvor...@bad.example.net > wrote:
> _ wrote:
> > On Thu, 01 Nov 2007 19:27:33 -0600, A Muzi wrote:
>
> >>> unforgive...@juno.com wrote:
> >>>> 2) You absolutely cannot presume from your measurements of pad
> >>>> spacing that the brake arms are twisting. This assumes that the front
> >>>> and rear edges are exactly the same distance from the pivot axis. In
> >>>> practice, this is going to vary depending on things like fork rake,
> >>>> rear dropout design, and how well the brakes are set up. It will in
> >>>> fact vary from front to rear, but not because of any difference in the
> >>>> calipers.
> >> Michael Press wrote:
> >>> You seem to be talking about fork offset here.
> >>> When the fork rake is varied the fork tip and
> >>> fork crown move together; and therefore the
> >>> brake pad position wrt the wheel rim remains
> >>> invariant.
> >> I assumed he meant the angle of the pad to the arm
>
> > You were correct. The following jim beam quote makes this clear:
>
> > "...shimano & campy dual pivot brake
> > calipers have a pivot action that increases toe on the pad as the
> > caliper closes."
>
> eh? the pad doesn't change relative to the arm - the arm is responsible
> for the angle swing. misunderstanding is no reason to misrepresent meaning.
>
>
>
> > He's not yet explained[1]:
>
> > a) why nobody else can measure see this; and/or
>
> this is r.b.t, buddy. this is home to people that can't tell the
> difference between rolled and cut thread, but feel free to argue about
> thread fatigue. you have people that correctly identify the math
> regarding camber thrust, but fail to make their point because they're
> intent on personal disagreement, not the facts. and you have people
> that claim to be able to eliminate metal fatigue while being ignorant of
> 100+ years of materials research proving the opposite.
>
>
>
> > b) just how these pivots change their axis of rotation
>
> but i have.
>
>
>
> > [1] this assumes that the standard beamboy response of the form "f**king
> > moron f**ktard" does not qualify as "explanation".
>
> you seem very intent on keeping that stuff alive. is your appearance at
> the same time as "jambo"'s disappearance mere coincidence?
You are replying to the infamous "jtaylor" of Canada, psychotic anti-
helmet nutcase extraordinaire. Rotsa ruck.
IMO, just ignore the insane lil' sack-o-shit.
|
| |
Date: 02 Nov 2007 08:16:12
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net > wrote:
> _ wrote:
> > On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
>
> >>>> What should I be measuring?
> >> "jim beam" <spamvor...@bad.example.net> a ?crit:
>
> >>> distance between the front tips of the brake pads with the caliper
> >>> open vs. caliper closed, and for the rear tips, open vs closed. when
> >>> open, the front tips are further apart than the rears. when closed,
> >>> the front tips are closer than the rears. [front caliper]
> >> I'm using the moulding seam of the brake block at the point it touches the
> >> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> >> of a convenient moulding mark) trying to pick a consistent point on the
> >> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> >> I can't detect any sign of the effect you say is there.
>
> >> James Thomson
>
> > Either beam's bushings are worn or the arms are loose on the pivots - that
> > was already pointed out.
>
> no, these are new calipers - in perfect condition.
>
> > It's impossible for an arm to pivot on a
> > cylindrical bushing and change the axis of rotation without another pivot
> > (which is, in essemce, what beamboy is claiming).
>
> no it's not. it's a simple geometry problem. you not figuring it out
> doesn't mean it's impossible - after all, it is observed to be happening.
Yes, it's a very simple geometry problem. Far simpler than your
explanation of magic pivots describes. The brake pads are adjustable
in a number of directions, one of which is rotation about the pad
fixing bolt. Look at the brake from the side with the mounting bolt
horizontal, and if the brake is set up to go on the rear, the rear
ends of the pads are going to be sitting lower than the front ends.
Assuming everything is set up square and parallel when the pads are
about a rim width apart, this will will give the appearance of the
front ends of the pads pointing inwards when you open the caliper all
the way. The rear ends of the pads moved farther out horizontally
because they are father from the pivot axes. Close the caliper all
the way and the front ends of the pads will be pointed out, because
they traveled a shorter horizontal distance for the same angle. Re-
adjust the pads so that the front ends are sitting lower than the rear
when viewed from the side, and you get the exact opposite behavior.
Adjust them level, and you're back to boring old parallel motion,
which is what everyone who actually wasted their time obeying your
command to measure their brakes observed. This is why you need to
prove your magic pivot theory by measuring from the arms not the
pads. The pads may be fixed, but they are not always fixed in a
position that supports your theory. If the second pivot really is
angled, there will also be some fore-aft translation of the arm
attached to it. Another reason why common sense dictates that this
would be an incredibly stupid way to design a brake.
|
| | |
Date: 02 Nov 2007 18:18:47
From: jim beam
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
>> _ wrote:
>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
>>>>>> What should I be measuring?
>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
>>>>> distance between the front tips of the brake pads with the caliper
>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
>>>>> open, the front tips are further apart than the rears. when closed,
>>>>> the front tips are closer than the rears. [front caliper]
>>>> I'm using the moulding seam of the brake block at the point it touches the
>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
>>>> of a convenient moulding mark) trying to pick a consistent point on the
>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
>>>> I can't detect any sign of the effect you say is there.
>>>> James Thomson
>>> Either beam's bushings are worn or the arms are loose on the pivots - that
>>> was already pointed out.
>> no, these are new calipers - in perfect condition.
>>
>>> It's impossible for an arm to pivot on a
>>> cylindrical bushing and change the axis of rotation without another pivot
>>> (which is, in essemce, what beamboy is claiming).
>> no it's not. it's a simple geometry problem. you not figuring it out
>> doesn't mean it's impossible - after all, it is observed to be happening.
>
> Yes, it's a very simple geometry problem. Far simpler than your
> explanation of magic pivots describes. The brake pads are adjustable
> in a number of directions, one of which is rotation about the pad
> fixing bolt.
duh. and when that bolt is tightened, they remain fixed. from that
point on, it doesn't matter /what/ you do, the /delta/ measurements i
did, remain the same.
> Look at the brake from the side with the mounting bolt
> horizontal, and if the brake is set up to go on the rear, the rear
> ends of the pads are going to be sitting lower than the front ends.
> Assuming everything is set up square and parallel when the pads are
> about a rim width apart, this will will give the appearance of the
> front ends of the pads pointing inwards when you open the caliper all
> the way. The rear ends of the pads moved farther out horizontally
> because they are father from the pivot axes. Close the caliper all
> the way and the front ends of the pads will be pointed out, because
> they traveled a shorter horizontal distance for the same angle. Re-
> adjust the pads so that the front ends are sitting lower than the rear
> when viewed from the side, and you get the exact opposite behavior.
> Adjust them level, and you're back to boring old parallel motion,
> which is what everyone who actually wasted their time obeying your
> command to measure their brakes observed. This is why you need to
> prove your magic pivot theory by measuring from the arms not the
> pads. The pads may be fixed, but they are not always fixed in a
> position that supports your theory. If the second pivot really is
> angled, there will also be some fore-aft translation of the arm
> attached to it. Another reason why common sense dictates that this
> would be an incredibly stupid way to design a brake.
>
says the guy that doesn't understand the concepts.
|
| | |
Date: 02 Nov 2007 16:32:31
From: _
Subject: Re: Mount front brakes on rear?
|
On Fri, 02 Nov 2007 08:16:12 -0700, unforgiven99@juno.com wrote:
> Yes, it's a very simple geometry problem. Far simpler than your
> explanation of magic pivots describes. The brake pads are adjustable
> in a number of directions, one of which is rotation about the pad
> fixing bolt. Look at the brake from the side with the mounting bolt
> horizontal, and if the brake is set up to go on the rear, the rear
> ends of the pads are going to be sitting lower than the front ends.
> Assuming everything is set up square and parallel when the pads are
> about a rim width apart, this will will give the appearance of the
> front ends of the pads pointing inwards when you open the caliper all
> the way. The rear ends of the pads moved farther out horizontally
> because they are father from the pivot axes. Close the caliper all
> the way and the front ends of the pads will be pointed out, because
> they traveled a shorter horizontal distance for the same angle. Re-
> adjust the pads so that the front ends are sitting lower than the rear
> when viewed from the side, and you get the exact opposite behavior.
> Adjust them level, and you're back to boring old parallel motion,
> which is what everyone who actually wasted their time obeying your
> command to measure their brakes observed. This is why you need to
> prove your magic pivot theory by measuring from the arms not the
> pads. The pads may be fixed, but they are not always fixed in a
> position that supports your theory. If the second pivot really is
> angled, there will also be some fore-aft translation of the arm
> attached to it. Another reason why common sense dictates that this
> would be an incredibly stupid way to design a brake.
And as the pivots are not magical (except perhaps in jim beam's world) such
action is no support for his asserting that this magical pivoting action is
a reason for not putting a back brake on the front - or vice-versa.
|
| |
Date: 02 Nov 2007 05:46:57
From: bjw@mambo.ucolick.org
Subject: Re: Mount front brakes on rear?
|
On Nov 1, 9:52 pm, jim beam <spamvor...@bad.example.net > wrote:
> b...@mambo.ucolick.org wrote:
> > On Nov 1, 6:44 am, "James Thomson" <yosnap...@hotmail.com> wrote:
> >> There's no mechanism to allow one arm to move the axis of the other. One
> >> pivots about the brake bolt, and the other pivots about an axis that's fixed
> >> with respect to the brake bolt, and parallel to the first.
>
> > This horse surely doesn't need to be beaten any more, but
> > I'll just point out that there are three pieces in a dual pivot
> > caliper - the two arms and a short link piece - and three
> > pivot joints. If you think about it for a little, it's very difficult
> > to see how it could work to have the axes of the brake
> > arm pivots canted with respect to each other, as the
> > short link would somehow have to bend or flex.
>
> not at all. the axis on the end of the short arm is skewed. as the
> short arm rotates about the central pivot, the angle of the outer pivot
> rotates.
Okay, now that I'm home and have a brake in my hand
to play with, I see that that pivot _could_ be canted
without causing the brakes to bind. However, on my
brakes (2 diff kinds of Shimano), it isn't canted.
Furthermore, if one canted that pivot, it would not
cause the amount of toe-in to change as the brakes
close. The brake pad on that side would be toed
in by the axis cant angle in open or closed position.
What would change is that the pad would move
slightly fore-aft as the brakes closed. I can't
see what purpose that would serve.
So either there's something unique about your model of
brake arms, or the pads are rotated in such a way that
the tips at one end are describing a smaller circle
and touching earlier, as another poster suggested.
Anyway, I have a Tektro rear DP brake mounted on the
front of a bike, with the brake pads swapped,
and it hasn't killed me yet. So either Tektro didn't
get the memo for this feature, or I am doomed to die
and am passing up my chance to live forever with
this brake miscegenation.
Ben
|
| |
Date: 02 Nov 2007 03:53:33
From: bjw@mambo.ucolick.org
Subject: Re: Mount front brakes on rear?
|
On Nov 1, 6:44 am, "James Thomson" <yosnap...@hotmail.com > wrote:
> "jim beam" <spamvor...@bad.example.net> a =E9crit:
>
> > b...@mambo.ucolick.org wrote:
> >> Also, one arm of the dual pivot brake pivots on the
> >> brake bolt and is surely tracking straight, not canted.
> > indeed, but the other pivot on the short arm isn't. and as it
> > swings through its arc, it tilts the axis angle for the "c" arm.
>
> There's no mechanism to allow one arm to move the axis of the other. One
> pivots about the brake bolt, and the other pivots about an axis that's fi=
xed
> with respect to the brake bolt, and parallel to the first.
This horse surely doesn't need to be beaten any more, but
I'll just point out that there are three pieces in a dual pivot
caliper - the two arms and a short link piece - and three
pivot joints. If you think about it for a little, it's very difficult
to see how it could work to have the axes of the brake
arm pivots canted with respect to each other, as the
short link would somehow have to bend or flex.
Ben
|
| | |
Date: 01 Nov 2007 21:52:57
From: jim beam
Subject: Re: Mount front brakes on rear?
|
bjw@mambo.ucolick.org wrote:
> On Nov 1, 6:44 am, "James Thomson" <yosnap...@hotmail.com> wrote:
>> "jim beam" <spamvor...@bad.example.net> a �crit:
>>
>>> b...@mambo.ucolick.org wrote:
>>>> Also, one arm of the dual pivot brake pivots on the
>>>> brake bolt and is surely tracking straight, not canted.
>>> indeed, but the other pivot on the short arm isn't. and as it
>>> swings through its arc, it tilts the axis angle for the "c" arm.
>> There's no mechanism to allow one arm to move the axis of the other. One
>> pivots about the brake bolt, and the other pivots about an axis that's fixed
>> with respect to the brake bolt, and parallel to the first.
>
> This horse surely doesn't need to be beaten any more, but
> I'll just point out that there are three pieces in a dual pivot
> caliper - the two arms and a short link piece - and three
> pivot joints. If you think about it for a little, it's very difficult
> to see how it could work to have the axes of the brake
> arm pivots canted with respect to each other, as the
> short link would somehow have to bend or flex.
not at all. the axis on the end of the short arm is skewed. as the
short arm rotates about the central pivot, the angle of the outer pivot
rotates.
|
| |
Date: 01 Nov 2007 08:11:10
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 1, 5:19 am, jim beam <spamvor...@bad.example.net > wrote:
> A Muzi wrote:
> >>>>>>> zarf...@gmail.com wrote:
> >>>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted
> >>>>>>>> them on
> >>>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
> >>>>>>>> considering mounting another front caliper on the rear wheel... Is
> >>>>>>>> this a good idea?
>
> >>>>>> jim beam wrote:
> >>>>>>> as pointed out by others, the bolt length thing is not a big deal.
> >>>>>>> however, you need to be aware that shimano & campy dual pivot brake
> >>>>>>> calipers have a pivot action that increases toe on the pad as the
> >>>>>>> caliper closes. [easily observed for yourself if you have the
> >>>>>>> caliper
> >>>>>>> in your hand - simply squeeze and note how the relative angles of
> >>>>>>> the
> >>>>>>> pads change as the lever arms move through their arc.] if a front
> >>>>>>> caliper is used on the rear, the toe is towards the rear of the
> >>>>>>> pads,
> >>>>>>> not the front, relative to rim direction.
>
> >>>>> Gary Young wrote:
> >>>>>> According to Shimano spare parts lists
> >>>>>> (http://tinyurl.com/2kecg9), the
> >>>>>> front and rear brakes are identical except for a bolt, a nut and a
> >>>>>> washer
> >>>>>> or spacer.
>
> >>>> jim beam <spamvor...@bad.example.net> wrote:
> >>>>> no, that's the parts list for the nuts and bolts, not the caliper
> >>>>> arms.
>
> >>>>> Gary Young wrote:
> >>>>>> How is this magical effect achieved?
>
> >>>> jim beam <spamvor...@bad.example.net> wrote:
> >>>>> "magical"??? how about you ask an objective question rather than a
> >>>>> sarcastic one that presupposes bullshit instead? you could also take
> >>>>> the time to look for the shimano mounting instructions which do indeed
> >>>>> advise against switching front/rear calipers.
> >>>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
> >>>>> and observe for yourself.
>
> >>>>>>> will you notice any effect in practice? maybe some brake squeal,
> >>>>>>> but
> >>>>>>> probably not. is it correct in theory? no. and iirc, there's a
> >>>>>>> warning in the shimano literature to the effect that each caliper is
> >>>>>>> specific to front or rear application and should not be
> >>>>>>> interchanged.
>
> >>> zarf...@gmail.com wrote:
> >>>> I took a look at the instructins,
> >>>> Not to put too fine a point on it, but the instructions actually say
> >>>> "Brakes designed for use as rear brakes should not be used as front
> >>>> brakes." Oddly, they do not contain a similar prohibition against
> >>>> using front brakes as rear brakes...
>
> >> A Muzi wrote:
> >>> I believe that's merely because your average human would forget to
> >>> reverse the brake shoes.
>
> > jim beam wrote:
> >> andrew, you have stock of dual pivot brakes, and measuring calipers.
> >> please perform the measurements i requested. i can do it, but i have
> >> to strip a bike and that's going to have to wait until the weekend.
>
> > Campagnolo are variegated (SP rear) and the Tektro are indeed identical
> > front to rear except bolt length.
>
> > In The Olden Days calipers were bent slightly to correct pad angle, new
> > calipers have orbital shoe adjustment washers. Am I missing something
> > here?
>
> repost:
>
> dura-ace, 7700 rear:
>
> open, front tips, 26.2mm, rear tips, 28.8mm, i.e. rear tips further apart.
>
> closed, front tips, 4.3mm, rear tips, 0mm [touching], i.e. front tips
> further apart.
>
> the change in toe is /clearly/ visible in operation.
>
> > Mounting a 'front' brake on a classic rear bridge with a nylock
> > nut is 'bad' because... ??
But is this because of the calipers or because of the pads? Anyway,
so what? It just means that he will have to wear the pads in to the
correct toe in--they might squeal a little bit for a couple of weeks.
Big deal.
|
| | |
Date: 01 Nov 2007 21:52:40
From: jim beam
Subject: Re: Mount front brakes on rear?
|
peteymills@hotmail.com wrote:
> On Nov 1, 5:19 am, jim beam <spamvor...@bad.example.net> wrote:
>> A Muzi wrote:
>>>>>>>>> zarf...@gmail.com wrote:
>>>>>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted
>>>>>>>>>> them on
>>>>>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>>>>>> this a good idea?
>>>>>>>> jim beam wrote:
>>>>>>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>>>>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>>>>>>> calipers have a pivot action that increases toe on the pad as the
>>>>>>>>> caliper closes. [easily observed for yourself if you have the
>>>>>>>>> caliper
>>>>>>>>> in your hand - simply squeeze and note how the relative angles of
>>>>>>>>> the
>>>>>>>>> pads change as the lever arms move through their arc.] if a front
>>>>>>>>> caliper is used on the rear, the toe is towards the rear of the
>>>>>>>>> pads,
>>>>>>>>> not the front, relative to rim direction.
>>>>>>> Gary Young wrote:
>>>>>>>> According to Shimano spare parts lists
>>>>>>>> (http://tinyurl.com/2kecg9), the
>>>>>>>> front and rear brakes are identical except for a bolt, a nut and a
>>>>>>>> washer
>>>>>>>> or spacer.
>>>>>> jim beam <spamvor...@bad.example.net> wrote:
>>>>>>> no, that's the parts list for the nuts and bolts, not the caliper
>>>>>>> arms.
>>>>>>> Gary Young wrote:
>>>>>>>> How is this magical effect achieved?
>>>>>> jim beam <spamvor...@bad.example.net> wrote:
>>>>>>> "magical"??? how about you ask an objective question rather than a
>>>>>>> sarcastic one that presupposes bullshit instead? you could also take
>>>>>>> the time to look for the shimano mounting instructions which do indeed
>>>>>>> advise against switching front/rear calipers.
>>>>>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>>>>>>> and observe for yourself.
>>>>>>>>> will you notice any effect in practice? maybe some brake squeal,
>>>>>>>>> but
>>>>>>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>>>>>>> warning in the shimano literature to the effect that each caliper is
>>>>>>>>> specific to front or rear application and should not be
>>>>>>>>> interchanged.
>>>>> zarf...@gmail.com wrote:
>>>>>> I took a look at the instructins,
>>>>>> Not to put too fine a point on it, but the instructions actually say
>>>>>> "Brakes designed for use as rear brakes should not be used as front
>>>>>> brakes." Oddly, they do not contain a similar prohibition against
>>>>>> using front brakes as rear brakes...
>>>> A Muzi wrote:
>>>>> I believe that's merely because your average human would forget to
>>>>> reverse the brake shoes.
>>> jim beam wrote:
>>>> andrew, you have stock of dual pivot brakes, and measuring calipers.
>>>> please perform the measurements i requested. i can do it, but i have
>>>> to strip a bike and that's going to have to wait until the weekend.
>>> Campagnolo are variegated (SP rear) and the Tektro are indeed identical
>>> front to rear except bolt length.
>>> In The Olden Days calipers were bent slightly to correct pad angle, new
>>> calipers have orbital shoe adjustment washers. Am I missing something
>>> here?
>> repost:
>>
>> dura-ace, 7700 rear:
>>
>> open, front tips, 26.2mm, rear tips, 28.8mm, i.e. rear tips further apart.
>>
>> closed, front tips, 4.3mm, rear tips, 0mm [touching], i.e. front tips
>> further apart.
>>
>> the change in toe is /clearly/ visible in operation.
>>
>>> Mounting a 'front' brake on a classic rear bridge with a nylock
>>> nut is 'bad' because... ??
>
> But is this because of the calipers or because of the pads?
calipers - the pads are fixed.
> Anyway,
> so what? It just means that he will have to wear the pads in to the
> correct toe in--they might squeal a little bit for a couple of weeks.
> Big deal.
that's right, trivialize what is not understood. this is r.b.t.
|
| | |
Date: 01 Nov 2007 17:10:53
From: _
Subject: Re: Mount front brakes on rear?
|
On Thu, 01 Nov 2007 08:11:10 -0700, peteymills@hotmail.com wrote:
> On Nov 1, 5:19 am, jim beam <spamvor...@bad.example.net> wrote:
>> A Muzi wrote:
>>>>>>>>> zarf...@gmail.com wrote:
>>>>>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted
>>>>>>>>>> them on
>>>>>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>>>>>> this a good idea?
>>
>>>>>>>> jim beam wrote:
>>>>>>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>>>>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>>>>>>> calipers have a pivot action that increases toe on the pad as the
>>>>>>>>> caliper closes. [easily observed for yourself if you have the
>>>>>>>>> caliper
>>>>>>>>> in your hand - simply squeeze and note how the relative angles of
>>>>>>>>> the
>>>>>>>>> pads change as the lever arms move through their arc.] if a front
>>>>>>>>> caliper is used on the rear, the toe is towards the rear of the
>>>>>>>>> pads,
>>>>>>>>> not the front, relative to rim direction.
>>
>>>>>>> Gary Young wrote:
>>>>>>>> According to Shimano spare parts lists
>>>>>>>> (http://tinyurl.com/2kecg9), the
>>>>>>>> front and rear brakes are identical except for a bolt, a nut and a
>>>>>>>> washer
>>>>>>>> or spacer.
>>
>>>>>> jim beam <spamvor...@bad.example.net> wrote:
>>>>>>> no, that's the parts list for the nuts and bolts, not the caliper
>>>>>>> arms.
>>
>>>>>>> Gary Young wrote:
>>>>>>>> How is this magical effect achieved?
>>
>>>>>> jim beam <spamvor...@bad.example.net> wrote:
>>>>>>> "magical"??? how about you ask an objective question rather than a
>>>>>>> sarcastic one that presupposes bullshit instead? you could also take
>>>>>>> the time to look for the shimano mounting instructions which do indeed
>>>>>>> advise against switching front/rear calipers.
>>>>>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>>>>>>> and observe for yourself.
>>
>>>>>>>>> will you notice any effect in practice? maybe some brake squeal,
>>>>>>>>> but
>>>>>>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>>>>>>> warning in the shimano literature to the effect that each caliper is
>>>>>>>>> specific to front or rear application and should not be
>>>>>>>>> interchanged.
>>
>>>>> zarf...@gmail.com wrote:
>>>>>> I took a look at the instructins,
>>>>>> Not to put too fine a point on it, but the instructions actually say
>>>>>> "Brakes designed for use as rear brakes should not be used as front
>>>>>> brakes." Oddly, they do not contain a similar prohibition against
>>>>>> using front brakes as rear brakes...
>>
>>>> A Muzi wrote:
>>>>> I believe that's merely because your average human would forget to
>>>>> reverse the brake shoes.
>>
>>> jim beam wrote:
>>>> andrew, you have stock of dual pivot brakes, and measuring calipers.
>>>> please perform the measurements i requested. i can do it, but i have
>>>> to strip a bike and that's going to have to wait until the weekend.
>>
>>> Campagnolo are variegated (SP rear) and the Tektro are indeed identical
>>> front to rear except bolt length.
>>
>>> In The Olden Days calipers were bent slightly to correct pad angle, new
>>> calipers have orbital shoe adjustment washers. Am I missing something
>>> here?
>>
>> repost:
>>
>> dura-ace, 7700 rear:
>>
>> open, front tips, 26.2mm, rear tips, 28.8mm, i.e. rear tips further apart.
>>
>> closed, front tips, 4.3mm, rear tips, 0mm [touching], i.e. front tips
>> further apart.
>>
>> the change in toe is /clearly/ visible in operation.
>>
>>> Mounting a 'front' brake on a classic rear bridge with a nylock
>>> nut is 'bad' because... ??
>
> But is this because of the calipers or because of the pads? Anyway,
> so what? It just means that he will have to wear the pads in to the
> correct toe in--they might squeal a little bit for a couple of weeks.
> Big deal.
He's said that it is the arms - remember that the origin of his claim for
magic pivots was that the arms were different between front and rear brakes
- and that this difference was what somehow made the arms twist as they
rotated.
Not that it's true in the real world, of course...
|
| | | |
Date: 01 Nov 2007 21:52:20
From: jim beam
Subject: Re: Mount front brakes on rear?
|
_ wrote:
> On Thu, 01 Nov 2007 08:11:10 -0700, peteymills@hotmail.com wrote:
>
>> On Nov 1, 5:19 am, jim beam <spamvor...@bad.example.net> wrote:
>>> A Muzi wrote:
>>>>>>>>>> zarf...@gmail.com wrote:
>>>>>>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted
>>>>>>>>>>> them on
>>>>>>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>>>>>>> this a good idea?
>>>>>>>>> jim beam wrote:
>>>>>>>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>>>>>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>>>>>>>> calipers have a pivot action that increases toe on the pad as the
>>>>>>>>>> caliper closes. [easily observed for yourself if you have the
>>>>>>>>>> caliper
>>>>>>>>>> in your hand - simply squeeze and note how the relative angles of
>>>>>>>>>> the
>>>>>>>>>> pads change as the lever arms move through their arc.] if a front
>>>>>>>>>> caliper is used on the rear, the toe is towards the rear of the
>>>>>>>>>> pads,
>>>>>>>>>> not the front, relative to rim direction.
>>>>>>>> Gary Young wrote:
>>>>>>>>> According to Shimano spare parts lists
>>>>>>>>> (http://tinyurl.com/2kecg9), the
>>>>>>>>> front and rear brakes are identical except for a bolt, a nut and a
>>>>>>>>> washer
>>>>>>>>> or spacer.
>>>>>>> jim beam <spamvor...@bad.example.net> wrote:
>>>>>>>> no, that's the parts list for the nuts and bolts, not the caliper
>>>>>>>> arms.
>>>>>>>> Gary Young wrote:
>>>>>>>>> How is this magical effect achieved?
>>>>>>> jim beam <spamvor...@bad.example.net> wrote:
>>>>>>>> "magical"??? how about you ask an objective question rather than a
>>>>>>>> sarcastic one that presupposes bullshit instead? you could also take
>>>>>>>> the time to look for the shimano mounting instructions which do indeed
>>>>>>>> advise against switching front/rear calipers.
>>>>>>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>>>>>>>> and observe for yourself.
>>>>>>>>>> will you notice any effect in practice? maybe some brake squeal,
>>>>>>>>>> but
>>>>>>>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>>>>>>>> warning in the shimano literature to the effect that each caliper is
>>>>>>>>>> specific to front or rear application and should not be
>>>>>>>>>> interchanged.
>>>>>> zarf...@gmail.com wrote:
>>>>>>> I took a look at the instructins,
>>>>>>> Not to put too fine a point on it, but the instructions actually say
>>>>>>> "Brakes designed for use as rear brakes should not be used as front
>>>>>>> brakes." Oddly, they do not contain a similar prohibition against
>>>>>>> using front brakes as rear brakes...
>>>>> A Muzi wrote:
>>>>>> I believe that's merely because your average human would forget to
>>>>>> reverse the brake shoes.
>>>> jim beam wrote:
>>>>> andrew, you have stock of dual pivot brakes, and measuring calipers.
>>>>> please perform the measurements i requested. i can do it, but i have
>>>>> to strip a bike and that's going to have to wait until the weekend.
>>>> Campagnolo are variegated (SP rear) and the Tektro are indeed identical
>>>> front to rear except bolt length.
>>>> In The Olden Days calipers were bent slightly to correct pad angle, new
>>>> calipers have orbital shoe adjustment washers. Am I missing something
>>>> here?
>>> repost:
>>>
>>> dura-ace, 7700 rear:
>>>
>>> open, front tips, 26.2mm, rear tips, 28.8mm, i.e. rear tips further apart.
>>>
>>> closed, front tips, 4.3mm, rear tips, 0mm [touching], i.e. front tips
>>> further apart.
>>>
>>> the change in toe is /clearly/ visible in operation.
>>>
>>>> Mounting a 'front' brake on a classic rear bridge with a nylock
>>>> nut is 'bad' because... ??
>> But is this because of the calipers or because of the pads? Anyway,
>> so what? It just means that he will have to wear the pads in to the
>> correct toe in--they might squeal a little bit for a couple of weeks.
>> Big deal.
>
> He's said that it is the arms - remember that the origin of his claim for
> magic pivots was that the arms were different between front and rear brakes
> - and that this difference was what somehow made the arms twist as they
> rotated.
no, don't put those words in my mouth.
imagine the following:
^
|
| |
Date: 01 Nov 2007 06:23:30
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 1, 9:08 am, "James Thomson" <yosnap...@hotmail.com > wrote:
> >> What should I be measuring?
>
> "jim beam" <spamvor...@bad.example.net> a =E9crit:
>
> > distance between the front tips of the brake pads with the caliper
> > open vs. caliper closed, and for the rear tips, open vs closed. when
> > open, the front tips are further apart than the rears. when closed,
> > the front tips are closer than the rears. [front caliper]
>
> I'm using the moulding seam of the brake block at the point it touches the
> holder as a reference point on the Ultegra 6500 brakes, and (in the absen=
ce
> of a convenient moulding mark) trying to pick a consistent point on the
> Centaur pad holder. The measurements are repeatable to within about 1mm, =
and
> I can't detect any sign of the effect you say is there.
>
> James Thomson
Just for laughs, try it again with the pads rotated one way or another
about the pad fixing bolts. You'll be able to reproduce jim's magical
toe in mechanism in either direction with the same caliper. The end
of the pad that's closest to the pivot axis is going to travel along a
shorter arc giving you a wonderful optical illusion that both arms of
the caliper are twisting in ways that they are physically unable to.
|
| |
Date: 01 Nov 2007 06:03:00
From:
Subject: Re: Mount front brakes on rear?
|
On Oct 31, 11:37 pm, jim beam <spamvor...@bad.example.net > wrote:
> unforgive...@juno.com wrote:
> > On Oct 30, 11:48 pm, jim beam <spamvor...@bad.example.net> wrote:
> >> Gary Young wrote:
> >>> On Sun, 28 Oct 2007 20:01:29 -0700, jim beam wrote:
> >>>> zarf...@gmail.com wrote:
> >>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> >>>>> my front wheel. My rear caliper is kinda corroded, and I was
> >>>>> considering mounting another front caliper on the rear wheel... Is
> >>>>> this a good idea?
> >>>> as pointed out by others, the bolt length thing is not a big deal.
> >>>> however, you need to be aware that shimano & campy dual pivot brake
> >>>> calipers have a pivot action that increases toe on the pad as the
> >>>> caliper closes. [easily observed for yourself if you have the caliper
> >>>> in your hand - simply squeeze and note how the relative angles of the
> >>>> pads change as the lever arms move through their arc.] if a front
> >>>> caliper is used on the rear, the toe is towards the rear of the pads,
> >>>> not the front, relative to rim direction.
> >>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
> >>> front and rear brakes are identical except for a bolt, a nut and a washer
> >>> or spacer.
> >> no, that's the parts list for the nuts and bolts, not the caliper arms.
>
> >>> How is this magical effect achieved?
> >> "magical"??? how about you ask an objective question rather than a
> >> sarcastic one that presupposes bullshit instead? you could also take
> >> the time to look for the shimano mounting instructions which do indeed
> >> advise against switching front/rear calipers.
>
> >> the answer is pivot angle. buy a campy or shimano dual pivot caliper
> >> and observe for yourself.
>
> >>>> will you notice any effect in practice? maybe some brake squeal, but
> >>>> probably not. is it correct in theory? no. and iirc, there's a
> >>>> warning in the shimano literature to the effect that each caliper is
> >>>> specific to front or rear application and should not be interchanged.
>
> > No, the answer is that either your pivot bolts are loose or the
> > bushings are worn. The effect you're describing is geometrically
> > impossible with fixed pivots no matter what angle they're at. There's
> > slop in the pivots, and it looks like the arms are twisting because
> > the cable attachments and springs are out of plane. The mechanism was
> > most certainly not designed to move that way.
>
> brand new dura-ace, i.e. no loose pivots or worn bushings, says you need
> to check your facts. supposition or disbelief are no a basis for
> "certainly" statements.
Allow me to clarify, since there seem to be some differences in the
ways that engineers and pretend metallurgists approach problems. A
few of the things that I considered.
1) In all of the press releases, web copy, and magazine reviews I've
ever seen, all filled with outlandish claims of technical achievement,
neither Campy nor Shimano has ever said anything about variable toe
in. This is not terribly surprising, as I'm looking at the Campy
installation manual right now, and they don't seem to believe that the
pads should be toed in to begin with. Also, despite all manner of
uptight safety warnings, there's no mention of not interchanging front
and rear calipers.
2) Two pivots do not always mean two degrees of freedom. This is the
kind of thing that we teach the real engineers to stop and think about
before they rip machines apart to see how they work. We teach it to
them before they reach legal drinking age, so I'll understand if
you're a bit behind the curve. In a dual pivot brake, one of the arms
is only rotating around one axis. If the second pivot were somehow
being used to twist one arm relative to one that's fixed in plane, the
result would be bad for pad wear, and potentially bad for the rim.
Now on to fact checking and supposition of fact as a basis for
"certainly" statements
1) My assumption of worn/loose pivots was based on my assumption that
you understand what you're talking about. I promise not to make that
mistake again.
2) You absolutely cannot presume from your measurements of pad
spacing that the brake arms are twisting. This assumes that the front
and rear edges are exactly the same distance from the pivot axis. In
practice, this is going to vary depending on things like fork rake,
rear dropout design, and how well the brakes are set up. It will in
fact vary from front to rear, but not because of any difference in the
calipers. Now, before instructing other people to take their bikes
apart to make the same useless measurements, perhaps you should take
the pads off of those shiny new Dura-Ace brakes and make some
measurements that actually prove some caliper twist that's different
between front and rear.
|
| | |
Date: 02 Nov 2007 00:07:40
From: Michael Press
Subject: Re: Mount front brakes on rear?
|
In article
<1193922180.413134.155920@50g2000hsm.googlegroups.com >,
unforgiven99@juno.com wrote:
> 2) You absolutely cannot presume from your measurements of pad
> spacing that the brake arms are twisting. This assumes that the front
> and rear edges are exactly the same distance from the pivot axis. In
> practice, this is going to vary depending on things like fork rake,
> rear dropout design, and how well the brakes are set up. It will in
> fact vary from front to rear, but not because of any difference in the
> calipers.
You seem to be talking about fork offset here.
When the fork rake is varied the fork tip and
fork crown move together; and therefore the
brake pad position wrt the wheel rim remains
invariant.
--
Michael Press
|
| | | |
Date: 01 Nov 2007 19:27:33
From: A Muzi
Subject: Re: Mount front brakes on rear?
|
> unforgiven99@juno.com wrote:
>> 2) You absolutely cannot presume from your measurements of pad
>> spacing that the brake arms are twisting. This assumes that the front
>> and rear edges are exactly the same distance from the pivot axis. In
>> practice, this is going to vary depending on things like fork rake,
>> rear dropout design, and how well the brakes are set up. It will in
>> fact vary from front to rear, but not because of any difference in the
>> calipers.
Michael Press wrote:
> You seem to be talking about fork offset here.
> When the fork rake is varied the fork tip and
> fork crown move together; and therefore the
> brake pad position wrt the wheel rim remains
> invariant.
I assumed he meant the angle of the pad to the arm
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| | | | |
Date: 02 Nov 2007 08:36:53
From: _
Subject: Re: Mount front brakes on rear?
|
On Thu, 01 Nov 2007 19:27:33 -0600, A Muzi wrote:
>> unforgiven99@juno.com wrote:
>>> 2) You absolutely cannot presume from your measurements of pad
>>> spacing that the brake arms are twisting. This assumes that the front
>>> and rear edges are exactly the same distance from the pivot axis. In
>>> practice, this is going to vary depending on things like fork rake,
>>> rear dropout design, and how well the brakes are set up. It will in
>>> fact vary from front to rear, but not because of any difference in the
>>> calipers.
>
> Michael Press wrote:
>> You seem to be talking about fork offset here.
>> When the fork rake is varied the fork tip and
>> fork crown move together; and therefore the
>> brake pad position wrt the wheel rim remains
>> invariant.
>
> I assumed he meant the angle of the pad to the arm
You were correct. The following jim beam quote makes this clear:
"...shimano & campy dual pivot brake
calipers have a pivot action that increases toe on the pad as the
caliper closes."
He's not yet explained[1]:
a) why nobody else can measure see this; and/or
b) just how these pivots change their axis of rotation
[1] this assumes that the standard beamboy response of the form "f**king
moron f**ktard" does not qualify as "explanation".
|
| | | | | |
Date: 02 Nov 2007 07:18:27
From: jim beam
Subject: Re: Mount front brakes on rear?
|
_ wrote:
> On Thu, 01 Nov 2007 19:27:33 -0600, A Muzi wrote:
>
>>> unforgiven99@juno.com wrote:
>>>> 2) You absolutely cannot presume from your measurements of pad
>>>> spacing that the brake arms are twisting. This assumes that the front
>>>> and rear edges are exactly the same distance from the pivot axis. In
>>>> practice, this is going to vary depending on things like fork rake,
>>>> rear dropout design, and how well the brakes are set up. It will in
>>>> fact vary from front to rear, but not because of any difference in the
>>>> calipers.
>> Michael Press wrote:
>>> You seem to be talking about fork offset here.
>>> When the fork rake is varied the fork tip and
>>> fork crown move together; and therefore the
>>> brake pad position wrt the wheel rim remains
>>> invariant.
>> I assumed he meant the angle of the pad to the arm
>
> You were correct. The following jim beam quote makes this clear:
>
> "...shimano & campy dual pivot brake
> calipers have a pivot action that increases toe on the pad as the
> caliper closes."
eh? the pad doesn't change relative to the arm - the arm is responsible
for the angle swing. misunderstanding is no reason to misrepresent meaning.
>
> He's not yet explained[1]:
>
> a) why nobody else can measure see this; and/or
this is r.b.t, buddy. this is home to people that can't tell the
difference between rolled and cut thread, but feel free to argue about
thread fatigue. you have people that correctly identify the math
regarding camber thrust, but fail to make their point because they're
intent on personal disagreement, not the facts. and you have people
that claim to be able to eliminate metal fatigue while being ignorant of
100+ years of materials research proving the opposite.
>
> b) just how these pivots change their axis of rotation
but i have.
>
> [1] this assumes that the standard beamboy response of the form "f**king
> moron f**ktard" does not qualify as "explanation".
you seem very intent on keeping that stuff alive. is your appearance at
the same time as "jambo"'s disappearance mere coincidence?
|
| | |
Date: 01 Nov 2007 14:50:48
From: _
Subject: Re: Mount front brakes on rear?
|
On Thu, 01 Nov 2007 06:03:00 -0700, unforgiven99@juno.com wrote:
In re. jim beam's assertion of magic pivots in shimano brakes:
> 1) My assumption of worn/loose pivots was based on my assumption that
> you understand what you're talking about. I promise not to make that
> mistake again.
Ten cents says jim beam will now start using insults as his strongest
support for this impossible claim.
|
| | | |
Date: 01 Nov 2007 12:33:51
From: A Muzi
Subject: Re: Mount front brakes on rear?
|
> On Thu, 01 Nov 2007 06:03:00 -0700, unforgiven99@juno.com wrote:
> In re. jim beam's assertion of magic pivots in shimano brakes:
>> 1) My assumption of worn/loose pivots was based on my assumption that
>> you understand what you're talking about. I promise not to make that
>> mistake again.
_ wrote:
> Ten cents says jim beam will now start using insults as his strongest
> support for this impossible claim.
At that point just read "Hitler" for "f**king moron f**ktard" and we can
close this.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| | |
Date: 01 Nov 2007 06:07:07
From: jim beam
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
> On Oct 31, 11:37 pm, jim beam <spamvor...@bad.example.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Oct 30, 11:48 pm, jim beam <spamvor...@bad.example.net> wrote:
>>>> Gary Young wrote:
>>>>> On Sun, 28 Oct 2007 20:01:29 -0700, jim beam wrote:
>>>>>> zarf...@gmail.com wrote:
>>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>>> this a good idea?
>>>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>>>> calipers have a pivot action that increases toe on the pad as the
>>>>>> caliper closes. [easily observed for yourself if you have the caliper
>>>>>> in your hand - simply squeeze and note how the relative angles of the
>>>>>> pads change as the lever arms move through their arc.] if a front
>>>>>> caliper is used on the rear, the toe is towards the rear of the pads,
>>>>>> not the front, relative to rim direction.
>>>>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
>>>>> front and rear brakes are identical except for a bolt, a nut and a washer
>>>>> or spacer.
>>>> no, that's the parts list for the nuts and bolts, not the caliper arms.
>>>>> How is this magical effect achieved?
>>>> "magical"??? how about you ask an objective question rather than a
>>>> sarcastic one that presupposes bullshit instead? you could also take
>>>> the time to look for the shimano mounting instructions which do indeed
>>>> advise against switching front/rear calipers.
>>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>>>> and observe for yourself.
>>>>>> will you notice any effect in practice? maybe some brake squeal, but
>>>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>>>> warning in the shimano literature to the effect that each caliper is
>>>>>> specific to front or rear application and should not be interchanged.
>>> No, the answer is that either your pivot bolts are loose or the
>>> bushings are worn. The effect you're describing is geometrically
>>> impossible with fixed pivots no matter what angle they're at. There's
>>> slop in the pivots, and it looks like the arms are twisting because
>>> the cable attachments and springs are out of plane. The mechanism was
>>> most certainly not designed to move that way.
>> brand new dura-ace, i.e. no loose pivots or worn bushings, says you need
>> to check your facts. supposition or disbelief are no a basis for
>> "certainly" statements.
>
> Allow me to clarify, since there seem to be some differences in the
> ways that engineers and pretend metallurgists approach problems. A
> few of the things that I considered.
> 1) In all of the press releases, web copy, and magazine reviews I've
> ever seen, all filled with outlandish claims of technical achievement,
> neither Campy nor Shimano has ever said anything about variable toe
> in. This is not terribly surprising, as I'm looking at the Campy
> installation manual right now, and they don't seem to believe that the
> pads should be toed in to begin with. Also, despite all manner of
> uptight safety warnings, there's no mention of not interchanging front
> and rear calipers.
> 2) Two pivots do not always mean two degrees of freedom. This is the
> kind of thing that we teach the real engineers to stop and think about
> before they rip machines apart to see how they work. We teach it to
> them before they reach legal drinking age, so I'll understand if
> you're a bit behind the curve. In a dual pivot brake, one of the arms
> is only rotating around one axis. If the second pivot were somehow
> being used to twist one arm relative to one that's fixed in plane, the
> result would be bad for pad wear, and potentially bad for the rim.
> Now on to fact checking and supposition of fact as a basis for
> "certainly" statements
> 1) My assumption of worn/loose pivots was based on my assumption that
> you understand what you're talking about. I promise not to make that
> mistake again.
> 2) You absolutely cannot presume from your measurements of pad
> spacing that the brake arms are twisting. This assumes that the front
> and rear edges are exactly the same distance from the pivot axis. In
> practice, this is going to vary depending on things like fork rake,
> rear dropout design, and how well the brakes are set up. It will in
> fact vary from front to rear, but not because of any difference in the
> calipers. Now, before instructing other people to take their bikes
> apart to make the same useless measurements, perhaps you should take
> the pads off of those shiny new Dura-Ace brakes and make some
> measurements that actually prove some caliper twist that's different
> between front and rear.
>
that "argument" is pure presumption. get a caliper and check for yourself.
|
| |
Date: 01 Nov 2007 01:05:31
From: bjw@mambo.ucolick.org
Subject: Re: Mount front brakes on rear?
|
On Oct 31, 8:55 pm, jim beam <spamvor...@bad.example.net > wrote:
> jim beam wrote:
> ok, i found a caliper still in a box. dura-ace, 7700 rear:
>
> open, front tips, 26.2mm, rear tips, 28.8mm, i.e. rear tips further apart.
>
> closed, front tips, 4.3mm, rear tips, 0mm [touching], i.e. front tips
> further apart.
>
> the change in toe is /clearly/ visible in operation.
I tried this with two types of Shimano dual pivot brakes
and I can't see any cammed toe-in effect, either on or
off a bike. I think I might be able to get one end to
touch first on the off-bike pair if the pads are
rotated up (no longer parallel to the brake bolt)
but that isn't how they are usually used.
Further, in usage, brakes are never closed to 0mm, since
rims are of order 18-20mm wide. Also, one arm of the
dual pivot brake pivots on the brake bolt and is surely
tracking straight, not canted.
I can't see this as a valid safety argument against
exchanging rear and front brake. You just have to
be careful to change around cartridge pads if you
have them to avoid pad ejection. And to make sure
the nut engages enough threads on the bolt, of course.
Naturally, when mounting any brake, you should
try to get the toe-in correct as the pads hit the
rim. The toe-in when the pads are off the rim only
affects brake clearance.
Ben
|
| | |
Date: 01 Nov 2007 06:02:52
From: jim beam
Subject: Re: Mount front brakes on rear?
|
bjw@mambo.ucolick.org wrote:
> On Oct 31, 8:55 pm, jim beam <spamvor...@bad.example.net> wrote:
>> jim beam wrote:
>> ok, i found a caliper still in a box. dura-ace, 7700 rear:
>>
>> open, front tips, 26.2mm, rear tips, 28.8mm, i.e. rear tips further apart.
>>
>> closed, front tips, 4.3mm, rear tips, 0mm [touching], i.e. front tips
>> further apart.
>>
>> the change in toe is /clearly/ visible in operation.
>
> I tried this with two types of Shimano dual pivot brakes
> and I can't see any cammed toe-in effect, either on or
> off a bike.
well, i've observed this on both campy and shimano. hence the above
measurements.
> I think I might be able to get one end to
> touch first on the off-bike pair if the pads are
> rotated up (no longer parallel to the brake bolt)
> but that isn't how they are usually used.
>
> Further, in usage, brakes are never closed to 0mm, since
> rims are of order 18-20mm wide.
full open to full close exaggerates the effect for sure, but the point
is that this operation is a design feature. i can only presume that
it's for increasing toe in operation.
> Also, one arm of the
> dual pivot brake pivots on the brake bolt and is surely
> tracking straight, not canted.
indeed, but the other pivot on the short arm isn't. and as it swings
through its arc, it tilts the axis angle for the "c" arm.
>
> I can't see this as a valid safety argument against
> exchanging rear and front brake. You just have to
> be careful to change around cartridge pads if you
> have them to avoid pad ejection.
well /that/ is a given - and not relevant to pivot angles.
> And to make sure
> the nut engages enough threads on the bolt, of course.
> Naturally, when mounting any brake, you should
> try to get the toe-in correct as the pads hit the
> rim.
my personal experience of this is that toe simply acts as a trap for
grit - all my bikes have orbital pad holders and i take the toe out.
and the caliper having its own toe action makes it even more unnecessary
imo.
> The toe-in when the pads are off the rim only
> affects brake clearance.
>
> Ben
>
|
| | | |
Date: 01 Nov 2007 14:44:42
From: James Thomson
Subject: Re: Mount front brakes on rear?
|
"jim beam" <spamvortex@bad.example.net > a écrit:
> bjw@mambo.ucolick.org wrote:
>> Also, one arm of the dual pivot brake pivots on the
>> brake bolt and is surely tracking straight, not canted.
> indeed, but the other pivot on the short arm isn't. and as it
> swings through its arc, it tilts the axis angle for the "c" arm.
There's no mechanism to allow one arm to move the axis of the other. One
pivots about the brake bolt, and the other pivots about an axis that's fixed
with respect to the brake bolt, and parallel to the first.
James Thomson
|
| |
Date: 31 Oct 2007 13:43:10
From:
Subject: Re: Mount front brakes on rear?
|
On Oct 30, 11:48 pm, jim beam <spamvor...@bad.example.net > wrote:
> Gary Young wrote:
> > On Sun, 28 Oct 2007 20:01:29 -0700, jim beam wrote:
>
> >> zarf...@gmail.com wrote:
> >>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> >>> my front wheel. My rear caliper is kinda corroded, and I was
> >>> considering mounting another front caliper on the rear wheel... Is
> >>> this a good idea?
>
> >> as pointed out by others, the bolt length thing is not a big deal.
> >> however, you need to be aware that shimano & campy dual pivot brake
> >> calipers have a pivot action that increases toe on the pad as the
> >> caliper closes. [easily observed for yourself if you have the caliper
> >> in your hand - simply squeeze and note how the relative angles of the
> >> pads change as the lever arms move through their arc.] if a front
> >> caliper is used on the rear, the toe is towards the rear of the pads,
> >> not the front, relative to rim direction.
>
> > According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
> > front and rear brakes are identical except for a bolt, a nut and a washer
> > or spacer.
>
> no, that's the parts list for the nuts and bolts, not the caliper arms.
>
> > How is this magical effect achieved?
>
> "magical"??? how about you ask an objective question rather than a
> sarcastic one that presupposes bullshit instead? you could also take
> the time to look for the shimano mounting instructions which do indeed
> advise against switching front/rear calipers.
>
> the answer is pivot angle. buy a campy or shimano dual pivot caliper
> and observe for yourself.
>
>
>
>
>
> >> will you notice any effect in practice? maybe some brake squeal, but
> >> probably not. is it correct in theory? no. and iirc, there's a
> >> warning in the shimano literature to the effect that each caliper is
> >> specific to front or rear application and should not be interchanged.- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
Hi,
I took a look at the instructins,
Not to put too fine a point on it, but the instructions actually say
"Brakes designed for use as rear brakes should not be used as front
brakes." Oddly, they do not contain a similar prohibition against
using front brakes as rear brakes...
regards,
dan
|
| | |
Date: 31 Oct 2007 16:01:35
From: A Muzi
Subject: Re: Mount front brakes on rear?
|
>>>> zarf...@gmail.com wrote:
>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>> this a good idea?
>>> jim beam wrote:
>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>> calipers have a pivot action that increases toe on the pad as the
>>>> caliper closes. [easily observed for yourself if you have the caliper
>>>> in your hand - simply squeeze and note how the relative angles of the
>>>> pads change as the lever arms move through their arc.] if a front
>>>> caliper is used on the rear, the toe is towards the rear of the pads,
>>>> not the front, relative to rim direction.
>> Gary Young wrote:
>>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
>>> front and rear brakes are identical except for a bolt, a nut and a washer
>>> or spacer.
> jim beam <spamvor...@bad.example.net> wrote:
>> no, that's the parts list for the nuts and bolts, not the caliper arms.
>> Gary Young wrote:
>>> How is this magical effect achieved?
> jim beam <spamvor...@bad.example.net> wrote:
>> "magical"??? how about you ask an objective question rather than a
>> sarcastic one that presupposes bullshit instead? you could also take
>> the time to look for the shimano mounting instructions which do indeed
>> advise against switching front/rear calipers.
>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>> and observe for yourself.
>>>> will you notice any effect in practice? maybe some brake squeal, but
>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>> warning in the shimano literature to the effect that each caliper is
>>>> specific to front or rear application and should not be interchanged.
zarfus1@gmail.com wrote:
> I took a look at the instructins,
> Not to put too fine a point on it, but the instructions actually say
> "Brakes designed for use as rear brakes should not be used as front
> brakes." Oddly, they do not contain a similar prohibition against
> using front brakes as rear brakes...
I believe that's merely because your average human would forget to
reverse the brake shoes.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| | | |
Date: 31 Oct 2007 20:36:59
From: jim beam
Subject: Re: Mount front brakes on rear?
|
A Muzi wrote:
>>>>> zarf...@gmail.com wrote:
>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>> this a good idea?
>
>>>> jim beam wrote:
>>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>>> calipers have a pivot action that increases toe on the pad as the
>>>>> caliper closes. [easily observed for yourself if you have the caliper
>>>>> in your hand - simply squeeze and note how the relative angles of the
>>>>> pads change as the lever arms move through their arc.] if a front
>>>>> caliper is used on the rear, the toe is towards the rear of the pads,
>>>>> not the front, relative to rim direction.
>
>>> Gary Young wrote:
>>>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
>>>> front and rear brakes are identical except for a bolt, a nut and a
>>>> washer
>>>> or spacer.
>
>> jim beam <spamvor...@bad.example.net> wrote:
>>> no, that's the parts list for the nuts and bolts, not the caliper arms.
>
>>> Gary Young wrote:
>>>> How is this magical effect achieved?
>
>> jim beam <spamvor...@bad.example.net> wrote:
>>> "magical"??? how about you ask an objective question rather than a
>>> sarcastic one that presupposes bullshit instead? you could also take
>>> the time to look for the shimano mounting instructions which do indeed
>>> advise against switching front/rear calipers.
>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>>> and observe for yourself.
>
>>>>> will you notice any effect in practice? maybe some brake squeal, but
>>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>>> warning in the shimano literature to the effect that each caliper is
>>>>> specific to front or rear application and should not be interchanged.
>
> zarfus1@gmail.com wrote:
>> I took a look at the instructins,
>> Not to put too fine a point on it, but the instructions actually say
>> "Brakes designed for use as rear brakes should not be used as front
>> brakes." Oddly, they do not contain a similar prohibition against
>> using front brakes as rear brakes...
>
> I believe that's merely because your average human would forget to
> reverse the brake shoes.
andrew, you have stock of dual pivot brakes, and measuring calipers.
please perform the measurements i requested. i can do it, but i have to
strip a bike and that's going to have to wait until the weekend.
|
| | | | |
Date: 31 Oct 2007 22:59:00
From: A Muzi
Subject: Re: Mount front brakes on rear?
|
>>>>>> zarf...@gmail.com wrote:
>>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>>> this a good idea?
>>
>>>>> jim beam wrote:
>>>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>>>> calipers have a pivot action that increases toe on the pad as the
>>>>>> caliper closes. [easily observed for yourself if you have the
>>>>>> caliper
>>>>>> in your hand - simply squeeze and note how the relative angles of the
>>>>>> pads change as the lever arms move through their arc.] if a front
>>>>>> caliper is used on the rear, the toe is towards the rear of the pads,
>>>>>> not the front, relative to rim direction.
>>>> Gary Young wrote:
>>>>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9),
>>>>> the
>>>>> front and rear brakes are identical except for a bolt, a nut and a
>>>>> washer
>>>>> or spacer.
>>> jim beam <spamvor...@bad.example.net> wrote:
>>>> no, that's the parts list for the nuts and bolts, not the caliper arms.
>>>> Gary Young wrote:
>>>>> How is this magical effect achieved?
>>> jim beam <spamvor...@bad.example.net> wrote:
>>>> "magical"??? how about you ask an objective question rather than a
>>>> sarcastic one that presupposes bullshit instead? you could also take
>>>> the time to look for the shimano mounting instructions which do indeed
>>>> advise against switching front/rear calipers.
>>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>>>> and observe for yourself.
>>>>>> will you notice any effect in practice? maybe some brake squeal, but
>>>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>>>> warning in the shimano literature to the effect that each caliper is
>>>>>> specific to front or rear application and should not be interchanged.
>> zarfus1@gmail.com wrote:
>>> I took a look at the instructins,
>>> Not to put too fine a point on it, but the instructions actually say
>>> "Brakes designed for use as rear brakes should not be used as front
>>> brakes." Oddly, they do not contain a similar prohibition against
>>> using front brakes as rear brakes...
> A Muzi wrote:
>> I believe that's merely because your average human would forget to
>> reverse the brake shoes.
jim beam wrote:
> andrew, you have stock of dual pivot brakes, and measuring calipers.
> please perform the measurements i requested. i can do it, but i have to
> strip a bike and that's going to have to wait until the weekend.
Campagnolo are variegated (SP rear) and the Tektro are indeed identical
front to rear except bolt length.
In The Olden Days calipers were bent slightly to correct pad angle, new
calipers have orbital shoe adjustment washers. Am I missing something
here? Mounting a 'front' brake on a classic rear bridge with a nylock
nut is 'bad' because... ??
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| | | | | |
Date: 31 Oct 2007 21:19:14
From: jim beam
Subject: Re: Mount front brakes on rear?
|
A Muzi wrote:
>>>>>>> zarf...@gmail.com wrote:
>>>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted
>>>>>>>> them on
>>>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>>>> this a good idea?
>>>
>>>>>> jim beam wrote:
>>>>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>>>>> calipers have a pivot action that increases toe on the pad as the
>>>>>>> caliper closes. [easily observed for yourself if you have the
>>>>>>> caliper
>>>>>>> in your hand - simply squeeze and note how the relative angles of
>>>>>>> the
>>>>>>> pads change as the lever arms move through their arc.] if a front
>>>>>>> caliper is used on the rear, the toe is towards the rear of the
>>>>>>> pads,
>>>>>>> not the front, relative to rim direction.
>
>>>>> Gary Young wrote:
>>>>>> According to Shimano spare parts lists
>>>>>> (http://tinyurl.com/2kecg9), the
>>>>>> front and rear brakes are identical except for a bolt, a nut and a
>>>>>> washer
>>>>>> or spacer.
>
>>>> jim beam <spamvor...@bad.example.net> wrote:
>>>>> no, that's the parts list for the nuts and bolts, not the caliper
>>>>> arms.
>
>>>>> Gary Young wrote:
>>>>>> How is this magical effect achieved?
>
>>>> jim beam <spamvor...@bad.example.net> wrote:
>>>>> "magical"??? how about you ask an objective question rather than a
>>>>> sarcastic one that presupposes bullshit instead? you could also take
>>>>> the time to look for the shimano mounting instructions which do indeed
>>>>> advise against switching front/rear calipers.
>>>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>>>>> and observe for yourself.
>
>>>>>>> will you notice any effect in practice? maybe some brake squeal,
>>>>>>> but
>>>>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>>>>> warning in the shimano literature to the effect that each caliper is
>>>>>>> specific to front or rear application and should not be
>>>>>>> interchanged.
>
>>> zarfus1@gmail.com wrote:
>>>> I took a look at the instructins,
>>>> Not to put too fine a point on it, but the instructions actually say
>>>> "Brakes designed for use as rear brakes should not be used as front
>>>> brakes." Oddly, they do not contain a similar prohibition against
>>>> using front brakes as rear brakes...
>
>> A Muzi wrote:
>>> I believe that's merely because your average human would forget to
>>> reverse the brake shoes.
>
> jim beam wrote:
>> andrew, you have stock of dual pivot brakes, and measuring calipers.
>> please perform the measurements i requested. i can do it, but i have
>> to strip a bike and that's going to have to wait until the weekend.
>
> Campagnolo are variegated (SP rear) and the Tektro are indeed identical
> front to rear except bolt length.
>
> In The Olden Days calipers were bent slightly to correct pad angle, new
> calipers have orbital shoe adjustment washers. Am I missing something
> here?
repost:
dura-ace, 7700 rear:
open, front tips, 26.2mm, rear tips, 28.8mm, i.e. rear tips further apart.
closed, front tips, 4.3mm, rear tips, 0mm [touching], i.e. front tips
further apart.
the change in toe is /clearly/ visible in operation.
> Mounting a 'front' brake on a classic rear bridge with a nylock
> nut is 'bad' because... ??
|
| | | | |
Date: 31 Oct 2007 20:55:31
From: jim beam
Subject: Re: Mount front brakes on rear?
|
jim beam wrote:
> A Muzi wrote:
>>>>>> zarf...@gmail.com wrote:
>>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>>> this a good idea?
>>
>>>>> jim beam wrote:
>>>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>>>> calipers have a pivot action that increases toe on the pad as the
>>>>>> caliper closes. [easily observed for yourself if you have the
>>>>>> caliper
>>>>>> in your hand - simply squeeze and note how the relative angles of the
>>>>>> pads change as the lever arms move through their arc.] if a front
>>>>>> caliper is used on the rear, the toe is towards the rear of the pads,
>>>>>> not the front, relative to rim direction.
>>
>>>> Gary Young wrote:
>>>>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9),
>>>>> the
>>>>> front and rear brakes are identical except for a bolt, a nut and a
>>>>> washer
>>>>> or spacer.
>>
>>> jim beam <spamvor...@bad.example.net> wrote:
>>>> no, that's the parts list for the nuts and bolts, not the caliper arms.
>>
>>>> Gary Young wrote:
>>>>> How is this magical effect achieved?
>>
>>> jim beam <spamvor...@bad.example.net> wrote:
>>>> "magical"??? how about you ask an objective question rather than a
>>>> sarcastic one that presupposes bullshit instead? you could also take
>>>> the time to look for the shimano mounting instructions which do indeed
>>>> advise against switching front/rear calipers.
>>>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>>>> and observe for yourself.
>>
>>>>>> will you notice any effect in practice? maybe some brake squeal, but
>>>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>>>> warning in the shimano literature to the effect that each caliper is
>>>>>> specific to front or rear application and should not be interchanged.
>>
>> zarfus1@gmail.com wrote:
>>> I took a look at the instructins,
>>> Not to put too fine a point on it, but the instructions actually say
>>> "Brakes designed for use as rear brakes should not be used as front
>>> brakes." Oddly, they do not contain a similar prohibition against
>>> using front brakes as rear brakes...
>>
>> I believe that's merely because your average human would forget to
>> reverse the brake shoes.
>
> andrew, you have stock of dual pivot brakes, and measuring calipers.
> please perform the measurements i requested. i can do it, but i have to
> strip a bike and that's going to have to wait until the weekend.
ok, i found a caliper still in a box. dura-ace, 7700 rear:
open, front tips, 26.2mm, rear tips, 28.8mm, i.e. rear tips further apart.
closed, front tips, 4.3mm, rear tips, 0mm [touching], i.e. front tips
further apart.
the change in toe is /clearly/ visible in operation.
|
| |
Date: 31 Oct 2007 10:39:33
From:
Subject: Re: Mount front brakes on rear?
|
On Oct 30, 11:48 pm, jim beam <spamvor...@bad.example.net > wrote:
> Gary Young wrote:
> > On Sun, 28 Oct 2007 20:01:29 -0700, jim beam wrote:
>
> >> zarf...@gmail.com wrote:
> >>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> >>> my front wheel. My rear caliper is kinda corroded, and I was
> >>> considering mounting another front caliper on the rear wheel... Is
> >>> this a good idea?
>
> >> as pointed out by others, the bolt length thing is not a big deal.
> >> however, you need to be aware that shimano & campy dual pivot brake
> >> calipers have a pivot action that increases toe on the pad as the
> >> caliper closes. [easily observed for yourself if you have the caliper
> >> in your hand - simply squeeze and note how the relative angles of the
> >> pads change as the lever arms move through their arc.] if a front
> >> caliper is used on the rear, the toe is towards the rear of the pads,
> >> not the front, relative to rim direction.
>
> > According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
> > front and rear brakes are identical except for a bolt, a nut and a washer
> > or spacer.
>
> no, that's the parts list for the nuts and bolts, not the caliper arms.
>
> > How is this magical effect achieved?
>
> "magical"??? how about you ask an objective question rather than a
> sarcastic one that presupposes bullshit instead? you could also take
> the time to look for the shimano mounting instructions which do indeed
> advise against switching front/rear calipers.
>
> the answer is pivot angle. buy a campy or shimano dual pivot caliper
> and observe for yourself.
>
>
>
> >> will you notice any effect in practice? maybe some brake squeal, but
> >> probably not. is it correct in theory? no. and iirc, there's a
> >> warning in the shimano literature to the effect that each caliper is
> >> specific to front or rear application and should not be interchanged.
No, the answer is that either your pivot bolts are loose or the
bushings are worn. The effect you're describing is geometrically
impossible with fixed pivots no matter what angle they're at. There's
slop in the pivots, and it looks like the arms are twisting because
the cable attachments and springs are out of plane. The mechanism was
most certainly not designed to move that way.
|
| | |
Date: 31 Oct 2007 20:37:12
From: jim beam
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
> On Oct 30, 11:48 pm, jim beam <spamvor...@bad.example.net> wrote:
>> Gary Young wrote:
>>> On Sun, 28 Oct 2007 20:01:29 -0700, jim beam wrote:
>>>> zarf...@gmail.com wrote:
>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>> this a good idea?
>>>> as pointed out by others, the bolt length thing is not a big deal.
>>>> however, you need to be aware that shimano & campy dual pivot brake
>>>> calipers have a pivot action that increases toe on the pad as the
>>>> caliper closes. [easily observed for yourself if you have the caliper
>>>> in your hand - simply squeeze and note how the relative angles of the
>>>> pads change as the lever arms move through their arc.] if a front
>>>> caliper is used on the rear, the toe is towards the rear of the pads,
>>>> not the front, relative to rim direction.
>>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
>>> front and rear brakes are identical except for a bolt, a nut and a washer
>>> or spacer.
>> no, that's the parts list for the nuts and bolts, not the caliper arms.
>>
>>> How is this magical effect achieved?
>> "magical"??? how about you ask an objective question rather than a
>> sarcastic one that presupposes bullshit instead? you could also take
>> the time to look for the shimano mounting instructions which do indeed
>> advise against switching front/rear calipers.
>>
>> the answer is pivot angle. buy a campy or shimano dual pivot caliper
>> and observe for yourself.
>>
>>
>>
>>>> will you notice any effect in practice? maybe some brake squeal, but
>>>> probably not. is it correct in theory? no. and iirc, there's a
>>>> warning in the shimano literature to the effect that each caliper is
>>>> specific to front or rear application and should not be interchanged.
>
> No, the answer is that either your pivot bolts are loose or the
> bushings are worn. The effect you're describing is geometrically
> impossible with fixed pivots no matter what angle they're at. There's
> slop in the pivots, and it looks like the arms are twisting because
> the cable attachments and springs are out of plane. The mechanism was
> most certainly not designed to move that way.
>
brand new dura-ace, i.e. no loose pivots or worn bushings, says you need
to check your facts. supposition or disbelief are no a basis for
"certainly" statements.
|
| |
Date: 31 Oct 2007 00:40:52
From: Gary Young
Subject: Re: Mount front brakes on rear?
|
On Tue, 30 Oct 2007 20:48:24 -0700, jim beam wrote:
> Gary Young wrote:
>> On Sun, 28 Oct 2007 20:01:29 -0700, jim beam wrote:
>>
>>> zarfus1@gmail.com wrote:
>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>> considering mounting another front caliper on the rear wheel... Is
>>>> this a good idea?
>>>>
>>> as pointed out by others, the bolt length thing is not a big deal.
>>> however, you need to be aware that shimano & campy dual pivot brake
>>> calipers have a pivot action that increases toe on the pad as the
>>> caliper closes. [easily observed for yourself if you have the caliper
>>> in your hand - simply squeeze and note how the relative angles of the
>>> pads change as the lever arms move through their arc.] if a front
>>> caliper is used on the rear, the toe is towards the rear of the pads,
>>> not the front, relative to rim direction.
>>
>>
>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
>> front and rear brakes are identical except for a bolt, a nut and a washer
>> or spacer.
>
> no, that's the parts list for the nuts and bolts, not the caliper arms.
>
Much as I hate to admit it, you are right that those lists are
inconclusive -- they list all the parts but the arms.
>
>> How is this magical effect achieved?
>
> "magical"??? how about you ask an objective question rather than a
> sarcastic one that presupposes bullshit instead? you could also take
> the time to look for the shimano mounting instructions which do indeed
> advise against switching front/rear calipers.
>
> the answer is pivot angle. buy a campy or shimano dual pivot caliper
> and observe for yourself.
>
>>
>>> will you notice any effect in practice? maybe some brake squeal, but
>>> probably not. is it correct in theory? no. and iirc, there's a
>>> warning in the shimano literature to the effect that each caliper is
>>> specific to front or rear application and should not be interchanged.
|
| |
Date: 30 Oct 2007 17:40:37
From: philcycles
Subject: Re: Mount front brakes on rear?
|
_ wrote:
>
> Or run a die down the longer bolt and cut the excess off.
Not really a good idea. These bolts are commonly chromed and the
chrome will ruin the die.
Phil Brown
|
| | |
Date: 31 Oct 2007 13:56:09
From: _
Subject: Re: Mount front brakes on rear?
|
On 30 Oct 2007 17:40:37 -0700, philcycles wrote:
> _ wrote:
>>
>> Or run a die down the longer bolt and cut the excess off.
>
> Not really a good idea. These bolts are commonly chromed and the
> chrome will ruin the die.
> Phil Brown
Not for one bolt. It's not a very thick plate, and while the wear on the
die will be greater unless you are looking at production quantities it
won't matter.
|
| |
Date: 30 Oct 2007 10:15:01
From:
Subject: Re: Mount front brakes on rear?
|
What if I were to put a spacer on the bolt supplied with the front
caliper to back the bolt down the hole in the seatstay? Would the
increased lever arm bend the bolt?
|
| | |
Date: 30 Oct 2007 11:36:55
From: Kerry Montgomery
Subject: Re: Mount front brakes on rear?
|
<zarfus1@gmail.com > wrote in message
news:1193764501.368127.290020@k79g2000hse.googlegroups.com...
> What if I were to put a spacer on the bolt supplied with the front
> caliper to back the bolt down the hole in the seatstay? Would the
> increased lever arm bend the bolt?
>
>
If the spacer goes between the brake bridge and the nut; should be OK. If
between the brake bridge and the caliper; maybe not so good.
Kerry
|
| |
Date: 30 Oct 2007 09:39:18
From: Gary Young
Subject: Re: Mount front brakes on rear?
|
On Sun, 28 Oct 2007 20:01:29 -0700, jim beam wrote:
> zarfus1@gmail.com wrote:
>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>> my front wheel. My rear caliper is kinda corroded, and I was
>> considering mounting another front caliper on the rear wheel... Is
>> this a good idea?
>>
>
> as pointed out by others, the bolt length thing is not a big deal.
> however, you need to be aware that shimano & campy dual pivot brake
> calipers have a pivot action that increases toe on the pad as the
> caliper closes. [easily observed for yourself if you have the caliper
> in your hand - simply squeeze and note how the relative angles of the
> pads change as the lever arms move through their arc.] if a front
> caliper is used on the rear, the toe is towards the rear of the pads,
> not the front, relative to rim direction.
According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
front and rear brakes are identical except for a bolt, a nut and a washer
or spacer. How is this magical effect achieved?
>
> will you notice any effect in practice? maybe some brake squeal, but
> probably not. is it correct in theory? no. and iirc, there's a
> warning in the shimano literature to the effect that each caliper is
> specific to front or rear application and should not be interchanged.
|
| | |
Date: 07 Nov 2007 08:27:51
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 6, 11:32 pm, jim beam <spamvor...@bad.example.net > wrote:
> unforgive...@juno.com wrote:
> > On Nov 4, 12:23 pm, jim beam <spamvor...@bad.example.net> wrote:
> >> unforgive...@juno.com wrote:
> >>> On Nov 3, 7:27 pm, jim beam <spamvor...@bad.example.net> wrote:
> >>>> unforgive...@juno.com wrote:
> >>>>> On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net> wrote:
> >>>>>> unforgive...@juno.com wrote:
> >>>>>>> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
> >>>>>>>> _ wrote:
> >>>>>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
> >>>>>>>>>>>> What should I be measuring?
> >>>>>>>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
> >>>>>>>>>>> distance between the front tips of the brake pads with the caliper
> >>>>>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
> >>>>>>>>>>> open, the front tips are further apart than the rears. when closed,
> >>>>>>>>>>> the front tips are closer than the rears. [front caliper]
> >>>>>>>>>> I'm using the moulding seam of the brake block at the point it touches the
> >>>>>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> >>>>>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
> >>>>>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> >>>>>>>>>> I can't detect any sign of the effect you say is there.
> >>>>>>>>>> James Thomson
> >>>>>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
> >>>>>>>>> was already pointed out.
> >>>>>>>> no, these are new calipers - in perfect condition.
> >>>>>>>>> It's impossible for an arm to pivot on a
> >>>>>>>>> cylindrical bushing and change the axis of rotation without another pivot
> >>>>>>>>> (which is, in essemce, what beamboy is claiming).
> >>>>>>>> no it's not. it's a simple geometry problem. you not figuring it out
> >>>>>>>> doesn't mean it's impossible - after all, it is observed to be happening.
> >>>>>>> Yes, it's a very simple geometry problem. Far simpler than your
> >>>>>>> explanation of magic pivots describes. The brake pads are adjustable
> >>>>>>> in a number of directions, one of which is rotation about the pad
> >>>>>>> fixing bolt.
> >>>>>> duh. and when that bolt is tightened, they remain fixed. from that
> >>>>>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
> >>>>>> did, remain the same.
> >>>>>>> Look at the brake from the side with the mounting bolt
> >>>>>>> horizontal, and if the brake is set up to go on the rear, the rear
> >>>>>>> ends of the pads are going to be sitting lower than the front ends.
> >>>>>>> Assuming everything is set up square and parallel when the pads are
> >>>>>>> about a rim width apart, this will will give the appearance of the
> >>>>>>> front ends of the pads pointing inwards when you open the caliper all
> >>>>>>> the way. The rear ends of the pads moved farther out horizontally
> >>>>>>> because they are father from the pivot axes. Close the caliper all
> >>>>>>> the way and the front ends of the pads will be pointed out, because
> >>>>>>> they traveled a shorter horizontal distance for the same angle. Re-
> >>>>>>> adjust the pads so that the front ends are sitting lower than the rear
> >>>>>>> when viewed from the side, and you get the exact opposite behavior.
> >>>>>>> Adjust them level, and you're back to boring old parallel motion,
> >>>>>>> which is what everyone who actually wasted their time obeying your
> >>>>>>> command to measure their brakes observed. This is why you need to
> >>>>>>> prove your magic pivot theory by measuring from the arms not the
> >>>>>>> pads. The pads may be fixed, but they are not always fixed in a
> >>>>>>> position that supports your theory. If the second pivot really is
> >>>>>>> angled, there will also be some fore-aft translation of the arm
> >>>>>>> attached to it. Another reason why common sense dictates that this
> >>>>>>> would be an incredibly stupid way to design a brake.
> >>>>>> says the guy that doesn't understand the concepts.
> >>>>> And what concepts would those be? That the distance traveled by a
> >>>>> point on a rigid rotating body does not depend on that point's
> >>>>> distance from the axis of rotation? Because that's what you're trying
> >>>>> to claim, and you're exactly right that I don't understand it. You
> >>>>> would be hard pressed to find anyone with a passing knowledge of
> >>>>> geometry who would buy that one. If you change the relative distances
> >>>>> of the pad ends from the pivot axes (in whichever direction you
> >>>>> believe them to be pointing) the delta measurements you performed will
> >>>>> change. Front or rear, and I'm looking at it right now on a single
> >>>>> pivot caliper.
> >>>> eh? you're basing your entire comment on single pivot???? holy carp.
> >>>>> The ends of the pads farthest from the pivot will
> >>>>> always be farther apart when the caliper is open, and closer together
> >>>>> when it's closed. How do you suppose it is that I can observe
> >>>>> something that you say absolutely has to be the result of one of a two
> >>>>> degree of freedom mechanism on a brake with only one degree of freedom?
> >>>> forget it. if you can't be bothered, nor can i.
> >>> No, I'm basing it on single pivot, dual pivot, and common sense.
> >> no, you're basing it on single pivot and underinformed presumption.
>
> >>> And
> >>> if your observation of changing brake pad distances can be observed in
> >>> a single pivot brake, then it absolutely cannot be proof of out of
> >>> plane rotation.
> >> rubbish.
>
> > Please tell me what it is that I'm presuming. I've duplicated your
> > progressive toe in measurements on both single and dual pivot brakes,
> > and I've changed it to a progressive toe out simply by changing the
> > pad adjustment. If either of those calipers has an arm that's
> > rotating out of plane, brake pad measurements simply are not
> > sufficient proof. Seeing how you're the only person on the planet
> > that believes that this rotation is happening, you're going to have to
> > do a lot more than stomp your feet and yell rubbish to convince me.
>
> i'm not trying to "convince" you - i simply want you to stop confusing
> yourself with irrelevancies about single pivot and pad adjustments [as
> long as they remain fixed, the deltas remain the same] and focus on
> observation of the dual pivot lever action! and even then, the ones i
> have stated. it may indeed be the case that some brakes don't have this
> feature, but as i have observed, campy veloce and record, and 7700
> dura-ace, these definitely do!
As long as they remain fixed where? Fix them in a different place and
the deltas disappear or reverse. This is not irrelevant. It shows
that while your observations of pad angle are necessary conditions to
prove your hypothesis of arm twisting, they are not sufficient. You
have not posted any observations of lever action. Only pad movement,
and only movement in directions that point to more realistic
explanations.
|
| | | |
Date: 08 Nov 2007 09:32:51
From: _
Subject: Re: Mount front brakes on rear?
|
On Wed, 07 Nov 2007 21:49:42 -0600, Tim McNamara wrote:
> _ wrote:
>> On Wed, 07 Nov 2007 08:27:51 -0800, unforgiven99@juno.com wrote:
>>
>>
>>>> observation of the dual pivot lever action! and even then, the
>>>> ones i have stated. it may indeed be the case that some brakes
>>>> don't have this feature, but as i have observed, campy veloce and
>>>> record, and 7700 dura-ace, these definitely do!
> >>
>>> As long as they remain fixed where? Fix them in a different place
>>> and the deltas disappear or reverse. This is not irrelevant. It
>>> shows that while your observations of pad angle are necessary
>>> conditions to prove your hypothesis of arm twisting, they are not
>>> sufficient. You have not posted any observations of lever action.
>>> Only pad movement, and only movement in directions that point to
>>> more realistic explanations.
>>
>> And further, since the arms do not twist, there is no support for
>> this being a reason for not interchanging front and rear brakes ("jim
>> beam"'s original assertion).
>>
>> Were it not "jim beam" on the other side of the argument, it would be
>> amazing that someone could continue to insist that an arm pivoting
>> on a single bushing can have two degrees of freedom...
>
> It depends on how much slop is in the bushing. The primary motion of
> rotating on the pivot would be large, but there are at least two other
> potential movements of the brake arm on the pivot: sliding along the
> axis of the pivot, and rocking on the pivot. The latter two would be
> driven by the rim pulling on the brake pad. These two movements would
> be very small, however, and unlikely to be of significant consequence.
> Might contribute to brake squeal, though. These motions are especially
> noticeable on brakes that mount on cantilever pivots.
"Slop in the pivots" aka worn bushings was indeed suggested as a reason for
"jim beam" seeing two degrees of freedom where geometry will allow but one;
one can but admire the charitable nature of such a poster.
|
| | | | |
Date: 08 Nov 2007 06:06:00
From: jim beam
Subject: Re: Mount front brakes on rear?
|
_ wrote:
> On Wed, 07 Nov 2007 21:49:42 -0600, Tim McNamara wrote:
>
>> _ wrote:
>>> On Wed, 07 Nov 2007 08:27:51 -0800, unforgiven99@juno.com wrote:
>>>
>>>
>>>>> observation of the dual pivot lever action! and even then, the
>>>>> ones i have stated. it may indeed be the case that some brakes
>>>>> don't have this feature, but as i have observed, campy veloce and
>>>>> record, and 7700 dura-ace, these definitely do!
>> >>
>>>> As long as they remain fixed where? Fix them in a different place
>>>> and the deltas disappear or reverse. This is not irrelevant. It
>>>> shows that while your observations of pad angle are necessary
>>>> conditions to prove your hypothesis of arm twisting, they are not
>>>> sufficient. You have not posted any observations of lever action.
>>>> Only pad movement, and only movement in directions that point to
>>>> more realistic explanations.
>>> And further, since the arms do not twist, there is no support for
>>> this being a reason for not interchanging front and rear brakes ("jim
>>> beam"'s original assertion).
>>>
>>> Were it not "jim beam" on the other side of the argument, it would be
>>> amazing that someone could continue to insist that an arm pivoting
>>> on a single bushing can have two degrees of freedom...
>> It depends on how much slop is in the bushing. The primary motion of
>> rotating on the pivot would be large, but there are at least two other
>> potential movements of the brake arm on the pivot: sliding along the
>> axis of the pivot, and rocking on the pivot. The latter two would be
>> driven by the rim pulling on the brake pad. These two movements would
>> be very small, however, and unlikely to be of significant consequence.
>> Might contribute to brake squeal, though. These motions are especially
>> noticeable on brakes that mount on cantilever pivots.
>
> "Slop in the pivots" aka worn bushings was indeed suggested as a reason
brand new dura-ace. no slop.
> for
> "jim beam" seeing two degrees of freedom where geometry will allow but one;
> one can but admire the charitable nature of such a poster.
found that geometry teacher yet?
|
| | | |
Date: 07 Nov 2007 20:26:45
From: jim beam
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
> On Nov 6, 11:32 pm, jim beam <spamvor...@bad.example.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Nov 4, 12:23 pm, jim beam <spamvor...@bad.example.net> wrote:
>>>> unforgive...@juno.com wrote:
>>>>> On Nov 3, 7:27 pm, jim beam <spamvor...@bad.example.net> wrote:
>>>>>> unforgive...@juno.com wrote:
>>>>>>> On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net> wrote:
>>>>>>>> unforgive...@juno.com wrote:
>>>>>>>>> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
>>>>>>>>>> _ wrote:
>>>>>>>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
>>>>>>>>>>>>>> What should I be measuring?
>>>>>>>>>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
>>>>>>>>>>>>> distance between the front tips of the brake pads with the caliper
>>>>>>>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
>>>>>>>>>>>>> open, the front tips are further apart than the rears. when closed,
>>>>>>>>>>>>> the front tips are closer than the rears. [front caliper]
>>>>>>>>>>>> I'm using the moulding seam of the brake block at the point it touches the
>>>>>>>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
>>>>>>>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
>>>>>>>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
>>>>>>>>>>>> I can't detect any sign of the effect you say is there.
>>>>>>>>>>>> James Thomson
>>>>>>>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
>>>>>>>>>>> was already pointed out.
>>>>>>>>>> no, these are new calipers - in perfect condition.
>>>>>>>>>>> It's impossible for an arm to pivot on a
>>>>>>>>>>> cylindrical bushing and change the axis of rotation without another pivot
>>>>>>>>>>> (which is, in essemce, what beamboy is claiming).
>>>>>>>>>> no it's not. it's a simple geometry problem. you not figuring it out
>>>>>>>>>> doesn't mean it's impossible - after all, it is observed to be happening.
>>>>>>>>> Yes, it's a very simple geometry problem. Far simpler than your
>>>>>>>>> explanation of magic pivots describes. The brake pads are adjustable
>>>>>>>>> in a number of directions, one of which is rotation about the pad
>>>>>>>>> fixing bolt.
>>>>>>>> duh. and when that bolt is tightened, they remain fixed. from that
>>>>>>>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
>>>>>>>> did, remain the same.
>>>>>>>>> Look at the brake from the side with the mounting bolt
>>>>>>>>> horizontal, and if the brake is set up to go on the rear, the rear
>>>>>>>>> ends of the pads are going to be sitting lower than the front ends.
>>>>>>>>> Assuming everything is set up square and parallel when the pads are
>>>>>>>>> about a rim width apart, this will will give the appearance of the
>>>>>>>>> front ends of the pads pointing inwards when you open the caliper all
>>>>>>>>> the way. The rear ends of the pads moved farther out horizontally
>>>>>>>>> because they are father from the pivot axes. Close the caliper all
>>>>>>>>> the way and the front ends of the pads will be pointed out, because
>>>>>>>>> they traveled a shorter horizontal distance for the same angle. Re-
>>>>>>>>> adjust the pads so that the front ends are sitting lower than the rear
>>>>>>>>> when viewed from the side, and you get the exact opposite behavior.
>>>>>>>>> Adjust them level, and you're back to boring old parallel motion,
>>>>>>>>> which is what everyone who actually wasted their time obeying your
>>>>>>>>> command to measure their brakes observed. This is why you need to
>>>>>>>>> prove your magic pivot theory by measuring from the arms not the
>>>>>>>>> pads. The pads may be fixed, but they are not always fixed in a
>>>>>>>>> position that supports your theory. If the second pivot really is
>>>>>>>>> angled, there will also be some fore-aft translation of the arm
>>>>>>>>> attached to it. Another reason why common sense dictates that this
>>>>>>>>> would be an incredibly stupid way to design a brake.
>>>>>>>> says the guy that doesn't understand the concepts.
>>>>>>> And what concepts would those be? That the distance traveled by a
>>>>>>> point on a rigid rotating body does not depend on that point's
>>>>>>> distance from the axis of rotation? Because that's what you're trying
>>>>>>> to claim, and you're exactly right that I don't understand it. You
>>>>>>> would be hard pressed to find anyone with a passing knowledge of
>>>>>>> geometry who would buy that one. If you change the relative distances
>>>>>>> of the pad ends from the pivot axes (in whichever direction you
>>>>>>> believe them to be pointing) the delta measurements you performed will
>>>>>>> change. Front or rear, and I'm looking at it right now on a single
>>>>>>> pivot caliper.
>>>>>> eh? you're basing your entire comment on single pivot???? holy carp.
>>>>>>> The ends of the pads farthest from the pivot will
>>>>>>> always be farther apart when the caliper is open, and closer together
>>>>>>> when it's closed. How do you suppose it is that I can observe
>>>>>>> something that you say absolutely has to be the result of one of a two
>>>>>>> degree of freedom mechanism on a brake with only one degree of freedom?
>>>>>> forget it. if you can't be bothered, nor can i.
>>>>> No, I'm basing it on single pivot, dual pivot, and common sense.
>>>> no, you're basing it on single pivot and underinformed presumption.
>>>>> And
>>>>> if your observation of changing brake pad distances can be observed in
>>>>> a single pivot brake, then it absolutely cannot be proof of out of
>>>>> plane rotation.
>>>> rubbish.
>>> Please tell me what it is that I'm presuming. I've duplicated your
>>> progressive toe in measurements on both single and dual pivot brakes,
>>> and I've changed it to a progressive toe out simply by changing the
>>> pad adjustment. If either of those calipers has an arm that's
>>> rotating out of plane, brake pad measurements simply are not
>>> sufficient proof. Seeing how you're the only person on the planet
>>> that believes that this rotation is happening, you're going to have to
>>> do a lot more than stomp your feet and yell rubbish to convince me.
>> i'm not trying to "convince" you - i simply want you to stop confusing
>> yourself with irrelevancies about single pivot and pad adjustments [as
>> long as they remain fixed, the deltas remain the same] and focus on
>> observation of the dual pivot lever action! and even then, the ones i
>> have stated. it may indeed be the case that some brakes don't have this
>> feature, but as i have observed, campy veloce and record, and 7700
>> dura-ace, these definitely do!
>
> As long as they remain fixed where? Fix them in a different place and
> the deltas disappear or reverse. This is not irrelevant. It shows
> that while your observations of pad angle are necessary conditions to
> prove your hypothesis of arm twisting, they are not sufficient. You
> have not posted any observations of lever action. Only pad movement,
> and only movement in directions that point to more realistic
> explanations.
>
read the thread again. i explained how it works back on 11/1 in a reply
to "_".
|
| | | |
Date: 08 Nov 2007 02:17:31
From: _
Subject: Re: Mount front brakes on rear?
|
On Wed, 07 Nov 2007 08:27:51 -0800, unforgiven99@juno.com wrote:
>> observation of the dual pivot lever action! and even then, the ones i
>> have stated. it may indeed be the case that some brakes don't have this
>> feature, but as i have observed, campy veloce and record, and 7700
>> dura-ace, these definitely do!
>
> As long as they remain fixed where? Fix them in a different place and
> the deltas disappear or reverse. This is not irrelevant. It shows
> that while your observations of pad angle are necessary conditions to
> prove your hypothesis of arm twisting, they are not sufficient. You
> have not posted any observations of lever action. Only pad movement,
> and only movement in directions that point to more realistic
> explanations.
And further, since the arms do not twist, there is no support for this
being a reason for not interchanging front and rear brakes ("jim beam"'s
original assertion).
Were it not "jim beam" on the other side of the argument, it would be
amazing that someone could continue to insist that an arm pivoting on a
single bushing can have two degrees of freedom...
|
| | | | |
Date: 07 Nov 2007 20:26:52
From: jim beam
Subject: Re: Mount front brakes on rear?
|
_ wrote:
> On Wed, 07 Nov 2007 08:27:51 -0800, unforgiven99@juno.com wrote:
>
>
>>> observation of the dual pivot lever action! and even then, the ones i
>>> have stated. it may indeed be the case that some brakes don't have this
>>> feature, but as i have observed, campy veloce and record, and 7700
>>> dura-ace, these definitely do!
>> As long as they remain fixed where? Fix them in a different place and
>> the deltas disappear or reverse. This is not irrelevant. It shows
>> that while your observations of pad angle are necessary conditions to
>> prove your hypothesis of arm twisting, they are not sufficient. You
>> have not posted any observations of lever action. Only pad movement,
>> and only movement in directions that point to more realistic
>> explanations.
>
> And further, since the arms do not twist, there is no support for this
> being a reason for not interchanging front and rear brakes ("jim beam"'s
> original assertion).
>
> Were it not "jim beam" on the other side of the argument, it would be
> amazing that someone could continue to insist that an arm pivoting on a
> single bushing can have two degrees of freedom...
still not good at geometry, are you.
|
| | | | |
Date: 07 Nov 2007 21:49:42
From: Tim McNamara
Subject: Re: Mount front brakes on rear?
|
_ wrote:
> On Wed, 07 Nov 2007 08:27:51 -0800, unforgiven99@juno.com wrote:
>
>
>>> observation of the dual pivot lever action! and even then, the
>>> ones i have stated. it may indeed be the case that some brakes
>>> don't have this feature, but as i have observed, campy veloce and
>>> record, and 7700 dura-ace, these definitely do!
>>
>> As long as they remain fixed where? Fix them in a different place
>> and the deltas disappear or reverse. This is not irrelevant. It
>> shows that while your observations of pad angle are necessary
>> conditions to prove your hypothesis of arm twisting, they are not
>> sufficient. You have not posted any observations of lever action.
>> Only pad movement, and only movement in directions that point to
>> more realistic explanations.
>
> And further, since the arms do not twist, there is no support for
> this being a reason for not interchanging front and rear brakes ("jim
> beam"'s original assertion).
>
> Were it not "jim beam" on the other side of the argument, it would be
> amazing that someone could continue to insist that an arm pivoting
> on a single bushing can have two degrees of freedom...
It depends on how much slop is in the bushing. The primary motion of
rotating on the pivot would be large, but there are at least two other
potential movements of the brake arm on the pivot: sliding along the
axis of the pivot, and rocking on the pivot. The latter two would be
driven by the rim pulling on the brake pad. These two movements would
be very small, however, and unlikely to be of significant consequence.
Might contribute to brake squeal, though. These motions are especially
noticeable on brakes that mount on cantilever pivots.
|
| | |
Date: 30 Oct 2007 20:48:24
From: jim beam
Subject: Re: Mount front brakes on rear?
|
Gary Young wrote:
> On Sun, 28 Oct 2007 20:01:29 -0700, jim beam wrote:
>
>> zarfus1@gmail.com wrote:
>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>> my front wheel. My rear caliper is kinda corroded, and I was
>>> considering mounting another front caliper on the rear wheel... Is
>>> this a good idea?
>>>
>> as pointed out by others, the bolt length thing is not a big deal.
>> however, you need to be aware that shimano & campy dual pivot brake
>> calipers have a pivot action that increases toe on the pad as the
>> caliper closes. [easily observed for yourself if you have the caliper
>> in your hand - simply squeeze and note how the relative angles of the
>> pads change as the lever arms move through their arc.] if a front
>> caliper is used on the rear, the toe is towards the rear of the pads,
>> not the front, relative to rim direction.
>
>
> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
> front and rear brakes are identical except for a bolt, a nut and a washer
> or spacer.
no, that's the parts list for the nuts and bolts, not the caliper arms.
> How is this magical effect achieved?
"magical"??? how about you ask an objective question rather than a
sarcastic one that presupposes bullshit instead? you could also take
the time to look for the shimano mounting instructions which do indeed
advise against switching front/rear calipers.
the answer is pivot angle. buy a campy or shimano dual pivot caliper
and observe for yourself.
>
>> will you notice any effect in practice? maybe some brake squeal, but
>> probably not. is it correct in theory? no. and iirc, there's a
>> warning in the shimano literature to the effect that each caliper is
>> specific to front or rear application and should not be interchanged.
|
| | |
Date: 30 Oct 2007 13:59:33
From: A Muzi
Subject: Re: Mount front brakes on rear?
|
>> zarfus1@gmail.com wrote:
>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>> my front wheel. My rear caliper is kinda corroded, and I was
>>> considering mounting another front caliper on the rear wheel... Is
>>> this a good idea?
> jim beam wrote:
>> as pointed out by others, the bolt length thing is not a big deal.
>> however, you need to be aware that shimano & campy dual pivot brake
>> calipers have a pivot action that increases toe on the pad as the
>> caliper closes. [easily observed for yourself if you have the caliper
>> in your hand - simply squeeze and note how the relative angles of the
>> pads change as the lever arms move through their arc.] if a front
>> caliper is used on the rear, the toe is towards the rear of the pads,
>> not the front, relative to rim direction.
Gary Young wrote:
> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
> front and rear brakes are identical except for a bolt, a nut and a washer
> or spacer. How is this magical effect achieved?
> jim beam wrote:
>> will you notice any effect in practice? maybe some brake squeal, but
>> probably not. is it correct in theory? no. and iirc, there's a
>> warning in the shimano literature to the effect that each caliper is
>> specific to front or rear application and should not be interchanged.
AFAIK rear and front calipers are only different after the mounting
bolt's installed and the shoes reversed. That's been standard industry
practice forever as there's no reason the other parts and hardware
should be different. (exceptions include 'self energizing' models)
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| | | |
Date: 30 Oct 2007 20:47:58
From: jim beam
Subject: Re: Mount front brakes on rear?
|
A Muzi wrote:
>>> zarfus1@gmail.com wrote:
>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>> considering mounting another front caliper on the rear wheel... Is
>>>> this a good idea?
>
>> jim beam wrote:
>>> as pointed out by others, the bolt length thing is not a big deal.
>>> however, you need to be aware that shimano & campy dual pivot brake
>>> calipers have a pivot action that increases toe on the pad as the
>>> caliper closes. [easily observed for yourself if you have the
>>> caliper in your hand - simply squeeze and note how the relative
>>> angles of the pads change as the lever arms move through their arc.]
>>> if a front caliper is used on the rear, the toe is towards the rear
>>> of the pads, not the front, relative to rim direction.
>
> Gary Young wrote:
>> According to Shimano spare parts lists (http://tinyurl.com/2kecg9), the
>> front and rear brakes are identical except for a bolt, a nut and a washer
>> or spacer. How is this magical effect achieved?
>
>> jim beam wrote:
>>> will you notice any effect in practice? maybe some brake squeal, but
>>> probably not. is it correct in theory? no. and iirc, there's a
>>> warning in the shimano literature to the effect that each caliper is
>>> specific to front or rear application and should not be interchanged.
>
> AFAIK rear and front calipers are only different after the mounting
> bolt's installed and the shoes reversed. That's been standard industry
> practice forever as there's no reason the other parts and hardware
> should be different. (exceptions include 'self energizing' models)
since you presumably have these things laying about your store, new in
box, why not dig out both brake calipers and measuring calipers and
measure what i describe?
|
| | | | |
Date: 09 Nov 2007 06:38:58
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 7, 11:26 pm, jim beam <spamvor...@bad.example.net > wrote:
> unforgive...@juno.com wrote:
> > On Nov 6, 11:32 pm, jim beam <spamvor...@bad.example.net> wrote:
> >> unforgive...@juno.com wrote:
> >>> On Nov 4, 12:23 pm, jim beam <spamvor...@bad.example.net> wrote:
> >>>> unforgive...@juno.com wrote:
> >>>>> On Nov 3, 7:27 pm, jim beam <spamvor...@bad.example.net> wrote:
> >>>>>> unforgive...@juno.com wrote:
> >>>>>>> On Nov 2, 9:18 pm, jim beam <spamvor...@bad.example.net> wrote:
> >>>>>>>> unforgive...@juno.com wrote:
> >>>>>>>>> On Nov 2, 12:53 am, jim beam <spamvor...@bad.example.net> wrote:
> >>>>>>>>>> _ wrote:
> >>>>>>>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
> >>>>>>>>>>>>>> What should I be measuring?
> >>>>>>>>>>>> "jim beam" <spamvor...@bad.example.net> a ?crit:
> >>>>>>>>>>>>> distance between the front tips of the brake pads with the caliper
> >>>>>>>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
> >>>>>>>>>>>>> open, the front tips are further apart than the rears. when closed,
> >>>>>>>>>>>>> the front tips are closer than the rears. [front caliper]
> >>>>>>>>>>>> I'm using the moulding seam of the brake block at the point it touches the
> >>>>>>>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> >>>>>>>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
> >>>>>>>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> >>>>>>>>>>>> I can't detect any sign of the effect you say is there.
> >>>>>>>>>>>> James Thomson
> >>>>>>>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
> >>>>>>>>>>> was already pointed out.
> >>>>>>>>>> no, these are new calipers - in perfect condition.
> >>>>>>>>>>> It's impossible for an arm to pivot on a
> >>>>>>>>>>> cylindrical bushing and change the axis of rotation without another pivot
> >>>>>>>>>>> (which is, in essemce, what beamboy is claiming).
> >>>>>>>>>> no it's not. it's a simple geometry problem. you not figuring it out
> >>>>>>>>>> doesn't mean it's impossible - after all, it is observed to be happening.
> >>>>>>>>> Yes, it's a very simple geometry problem. Far simpler than your
> >>>>>>>>> explanation of magic pivots describes. The brake pads are adjustable
> >>>>>>>>> in a number of directions, one of which is rotation about the pad
> >>>>>>>>> fixing bolt.
> >>>>>>>> duh. and when that bolt is tightened, they remain fixed. from that
> >>>>>>>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
> >>>>>>>> did, remain the same.
> >>>>>>>>> Look at the brake from the side with the mounting bolt
> >>>>>>>>> horizontal, and if the brake is set up to go on the rear, the rear
> >>>>>>>>> ends of the pads are going to be sitting lower than the front ends.
> >>>>>>>>> Assuming everything is set up square and parallel when the pads are
> >>>>>>>>> about a rim width apart, this will will give the appearance of the
> >>>>>>>>> front ends of the pads pointing inwards when you open the caliper all
> >>>>>>>>> the way. The rear ends of the pads moved farther out horizontally
> >>>>>>>>> because they are father from the pivot axes. Close the caliper all
> >>>>>>>>> the way and the front ends of the pads will be pointed out, because
> >>>>>>>>> they traveled a shorter horizontal distance for the same angle. Re-
> >>>>>>>>> adjust the pads so that the front ends are sitting lower than the rear
> >>>>>>>>> when viewed from the side, and you get the exact opposite behavior.
> >>>>>>>>> Adjust them level, and you're back to boring old parallel motion,
> >>>>>>>>> which is what everyone who actually wasted their time obeying your
> >>>>>>>>> command to measure their brakes observed. This is why you need to
> >>>>>>>>> prove your magic pivot theory by measuring from the arms not the
> >>>>>>>>> pads. The pads may be fixed, but they are not always fixed in a
> >>>>>>>>> position that supports your theory. If the second pivot really is
> >>>>>>>>> angled, there will also be some fore-aft translation of the arm
> >>>>>>>>> attached to it. Another reason why common sense dictates that this
> >>>>>>>>> would be an incredibly stupid way to design a brake.
> >>>>>>>> says the guy that doesn't understand the concepts.
> >>>>>>> And what concepts would those be? That the distance traveled by a
> >>>>>>> point on a rigid rotating body does not depend on that point's
> >>>>>>> distance from the axis of rotation? Because that's what you're trying
> >>>>>>> to claim, and you're exactly right that I don't understand it. You
> >>>>>>> would be hard pressed to find anyone with a passing knowledge of
> >>>>>>> geometry who would buy that one. If you change the relative distances
> >>>>>>> of the pad ends from the pivot axes (in whichever direction you
> >>>>>>> believe them to be pointing) the delta measurements you performed will
> >>>>>>> change. Front or rear, and I'm looking at it right now on a single
> >>>>>>> pivot caliper.
> >>>>>> eh? you're basing your entire comment on single pivot???? holy carp.
> >>>>>>> The ends of the pads farthest from the pivot will
> >>>>>>> always be farther apart when the caliper is open, and closer together
> >>>>>>> when it's closed. How do you suppose it is that I can observe
> >>>>>>> something that you say absolutely has to be the result of one of a two
> >>>>>>> degree of freedom mechanism on a brake with only one degree of freedom?
> >>>>>> forget it. if you can't be bothered, nor can i.
> >>>>> No, I'm basing it on single pivot, dual pivot, and common sense.
> >>>> no, you're basing it on single pivot and underinformed presumption.
> >>>>> And
> >>>>> if your observation of changing brake pad distances can be observed in
> >>>>> a single pivot brake, then it absolutely cannot be proof of out of
> >>>>> plane rotation.
> >>>> rubbish.
> >>> Please tell me what it is that I'm presuming. I've duplicated your
> >>> progressive toe in measurements on both single and dual pivot brakes,
> >>> and I've changed it to a progressive toe out simply by changing the
> >>> pad adjustment. If either of those calipers has an arm that's
> >>> rotating out of plane, brake pad measurements simply are not
> >>> sufficient proof. Seeing how you're the only person on the planet
> >>> that believes that this rotation is happening, you're going to have to
> >>> do a lot more than stomp your feet and yell rubbish to convince me.
> >> i'm not trying to "convince" you - i simply want you to stop confusing
> >> yourself with irrelevancies about single pivot and pad adjustments [as
> >> long as they remain fixed, the deltas remain the same] and focus on
> >> observation of the dual pivot lever action! and even then, the ones i
> >> have stated. it may indeed be the case that some brakes don't have this
> >> feature, but as i have observed, campy veloce and record, and 7700
> >> dura-ace, these definitely do!
>
> > As long as they remain fixed where? Fix them in a different place and
> > the deltas disappear or reverse. This is not irrelevant. It shows
> > that while your observations of pad angle are necessary conditions to
> > prove your hypothesis of arm twisting, they are not sufficient. You
> > have not posted any observations of lever action. Only pad movement,
> > and only movement in directions that point to more realistic
> > explanations.
>
> read the thread again. i explained how it works back on 11/1 in a reply
> to "_".
You didn't explain how it works. You explained how it could work, but
your observations are not sufficient to support your explanation.
Your observation of changing relative brake pad distances may be
explained by either the orientation of the brake pads (which you
refuse to accept) or an out of plane orientation of the second pivot
(which the rest of us refuse to accept). The tie breaker is fore-aft
pad translation. One arm of the dual pivot caliper cannot twist.
It's rotating about the mounting bolt, with one degree of freedom. If
there is something special about that second pivot, which
differentiates the caliper as front or rear by making the arm twist
one way or another, then the pad attached to it will be moving fore
and aft relative to the other pad as the caliper opens and closes.
Since you have such a great geometry teacher, this should be obvious.
This is not happening though, and nobody has claimed to have observed
it happening, including yourself.
|
| | | | | |
Date: 09 Nov 2007 09:10:47
From: Tim McNamara
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
<snip much verbiage >
> On Nov 7, 11:26 pm, jim beam <spamvor...@bad.example.net> wrote:
>
>> read the thread again. i explained how it works back on 11/1 in a
>> reply to "_".
>
> You didn't explain how it works. You explained how it could work,
> but your observations are not sufficient to support your explanation.
> Your observation of changing relative brake pad distances may be
> explained by either the orientation of the brake pads (which you
> refuse to accept) or an out of plane orientation of the second pivot
> (which the rest of us refuse to accept). The tie breaker is fore-aft
> pad translation. One arm of the dual pivot caliper cannot twist.
If that was the case, then brake squeal would not happen. The caliper
arm can flex in at least two ways; the longer the distance from the
pivot to the brake pad, the greater this is an issue.
> It's rotating about the mounting bolt, with one degree of freedom.
That's assuming a perfect bearing, which doesn't exist. There are at
least three degrees of freedom there. One is large, the other two are
(or should be) very small.
> If there is something special about that second pivot, which
> differentiates the caliper as front or rear by making the arm twist
> one way or another, then the pad attached to it will be moving fore
> and aft relative to the other pad as the caliper opens and closes.
> Since you have such a great geometry teacher, this should be obvious.
> This is not happening though, and nobody has claimed to have
> observed it happening, including yourself.
Grab a brake lever and squeeze tight. Now rock the bike back and forth.
Do the brake pads move relative to the fork blades or seatstays? On
my bikes I can detect a very small fore and aft movement by placing my
finger between the brake and the frame. There is no visual movement of
the pads vis a vis the frame on my bikes, except on one with
cantilever brakes- there's much more play in the pivots as well as twice
as many pivots. On all my bikes the movement is more pronounced for the
front brake, which is probably due to fork flex. Note that the forces
in this little experiment are much smaller than actual braking forces
when riding. In real life, my guess (and it is a guess) is that frame
flex would account for more undesirable movement of the brake pads than
odd motions in the pivot.
Strain gauges on the brake caliper arms might answer the question.
Anybody here got some? Maybe a project for Fogel Labs!
|
| | | | |
Date: 31 Oct 2007 15:33:32
From: James Thomson
Subject: Re: Mount front brakes on rear?
|
"jim beam" <spamvortex@bad.example.net > a écrit:
>>>> shimano & campy dual pivot brake calipers have a pivot action that
>>>> increases toe on the pad
>>>> as the caliper closes. [easily observed for yourself if you
>>>> have the caliper in your hand - simply squeeze and note
>>>> how the relative angles of the pads change as the lever
>>>> arms move through their arc.]
> since you presumably have these things laying about your store,
> new in box, why not dig out both brake calipers and measuring
> calipers and measure what i describe?
What should I be measuring? I have new (previous generation) Campag Centaur
and Shimano Ultegra calipers here on my desk, and I can't see or measure any
change in angle between the pads relative to the plane of the rim. In fact I
can't readily see how that would be possible, as the pivot of one arm is
co-axial with the brake bolt in each case (and that's true of all dual-pivot
brakes I've seen).
James Thomson
|
| | | | | |
Date: 31 Oct 2007 20:36:47
From: jim beam
Subject: Re: Mount front brakes on rear?
|
James Thomson wrote:
> "jim beam" <spamvortex@bad.example.net> a �crit:
>
>>>>> shimano & campy dual pivot brake calipers have a pivot action that
>>>>> increases toe on the pad
>>>>> as the caliper closes. [easily observed for yourself if you
>>>>> have the caliper in your hand - simply squeeze and note
>>>>> how the relative angles of the pads change as the lever
>>>>> arms move through their arc.]
>
>> since you presumably have these things laying about your store,
>> new in box, why not dig out both brake calipers and measuring
>> calipers and measure what i describe?
>
> What should I be measuring?
distance between the front tips of the brake pads with the caliper open
vs. caliper closed, and for the rear tips, open vs closed. when open,
the front tips are further apart than the rears. when closed, the front
tips are closer than the rears. [front caliper]
> I have new (previous generation) Campag Centaur
> and Shimano Ultegra calipers here on my desk, and I can't see or measure any
> change in angle between the pads relative to the plane of the rim. In fact I
> can't readily see how that would be possible, as the pivot of one arm is
> co-axial with the brake bolt in each case (and that's true of all dual-pivot
> brakes I've seen).
>
> James Thomson
>
>
|
| | | | | | |
Date: 09 Nov 2007 07:37:18
From:
Subject: Re: Mount front brakes on rear?
|
On Nov 9, 10:10 am, Tim McNamara <tim...@bitstream.net > wrote:
> unforgive...@juno.com wrote:
>
> <snip much verbiage>
>
> > On Nov 7, 11:26 pm, jim beam <spamvor...@bad.example.net> wrote:
>
> >> read the thread again. i explained how it works back on 11/1 in a
> >> reply to "_".
>
> > You didn't explain how it works. You explained how it could work,
> > but your observations are not sufficient to support your explanation.
> > Your observation of changing relative brake pad distances may be
> > explained by either the orientation of the brake pads (which you
> > refuse to accept) or an out of plane orientation of the second pivot
> > (which the rest of us refuse to accept). The tie breaker is fore-aft
> > pad translation. One arm of the dual pivot caliper cannot twist.
>
> If that was the case, then brake squeal would not happen. The caliper
> arm can flex in at least two ways; the longer the distance from the
> pivot to the brake pad, the greater this is an issue.
>
> > It's rotating about the mounting bolt, with one degree of freedom.
>
> That's assuming a perfect bearing, which doesn't exist. There are at
> least three degrees of freedom there. One is large, the other two are
> (or should be) very small.
>
> > If there is something special about that second pivot, which
> > differentiates the caliper as front or rear by making the arm twist
> > one way or another, then the pad attached to it will be moving fore
> > and aft relative to the other pad as the caliper opens and closes.
> > Since you have such a great geometry teacher, this should be obvious.
> > This is not happening though, and nobody has claimed to have
> > observed it happening, including yourself.
>
> Grab a brake lever and squeeze tight. Now rock the bike back and forth.
> Do the brake pads move relative to the fork blades or seatstays? On
> my bikes I can detect a very small fore and aft movement by placing my
> finger between the brake and the frame. There is no visual movement of
> the pads vis a vis the frame on my bikes, except on one with
> cantilever brakes- there's much more play in the pivots as well as twice
> as many pivots. On all my bikes the movement is more pronounced for the
> front brake, which is probably due to fork flex. Note that the forces
> in this little experiment are much smaller than actual braking forces
> when riding. In real life, my guess (and it is a guess) is that frame
> flex would account for more undesirable movement of the brake pads than
> odd motions in the pivot.
>
> Strain gauges on the brake caliper arms might answer the question.
> Anybody here got some? Maybe a project for Fogel Labs!
All very good points, but the ways in which a caliper deflects under
load aren't the issue here. There's a claim here that there's an arm
twisting under no load that's a result of a design feature. There
has been no credible evidence to support this, only optical tricks.
|
| | | | | | | |
Date: 09 Nov 2007 19:55:39
From: jim beam
Subject: Re: Mount front brakes on rear?
|
unforgiven99@juno.com wrote:
> On Nov 9, 10:10 am, Tim McNamara <tim...@bitstream.net> wrote:
>> unforgive...@juno.com wrote:
>>
>> <snip much verbiage>
>>
>>> On Nov 7, 11:26 pm, jim beam <spamvor...@bad.example.net> wrote:
>>>> read the thread again. i explained how it works back on 11/1 in a
>>>> reply to "_".
>>> You didn't explain how it works. You explained how it could work,
>>> but your observations are not sufficient to support your explanation.
>>> Your observation of changing relative brake pad distances may be
>>> explained by either the orientation of the brake pads (which you
>>> refuse to accept) or an out of plane orientation of the second pivot
>>> (which the rest of us refuse to accept). The tie breaker is fore-aft
>>> pad translation. One arm of the dual pivot caliper cannot twist.
>> If that was the case, then brake squeal would not happen. The caliper
>> arm can flex in at least two ways; the longer the distance from the
>> pivot to the brake pad, the greater this is an issue.
>>
>>> It's rotating about the mounting bolt, with one degree of freedom.
>> That's assuming a perfect bearing, which doesn't exist. There are at
>> least three degrees of freedom there. One is large, the other two are
>> (or should be) very small.
>>
>>> If there is something special about that second pivot, which
>>> differentiates the caliper as front or rear by making the arm twist
>>> one way or another, then the pad attached to it will be moving fore
>>> and aft relative to the other pad as the caliper opens and closes.
>>> Since you have such a great geometry teacher, this should be obvious.
>>> This is not happening though, and nobody has claimed to have
>>> observed it happening, including yourself.
>> Grab a brake lever and squeeze tight. Now rock the bike back and forth.
>> Do the brake pads move relative to the fork blades or seatstays? On
>> my bikes I can detect a very small fore and aft movement by placing my
>> finger between the brake and the frame. There is no visual movement of
>> the pads vis a vis the frame on my bikes, except on one with
>> cantilever brakes- there's much more play in the pivots as well as twice
>> as many pivots. On all my bikes the movement is more pronounced for the
>> front brake, which is probably due to fork flex. Note that the forces
>> in this little experiment are much smaller than actual braking forces
>> when riding. In real life, my guess (and it is a guess) is that frame
>> flex would account for more undesirable movement of the brake pads than
>> odd motions in the pivot.
>>
>> Strain gauges on the brake caliper arms might answer the question.
>> Anybody here got some? Maybe a project for Fogel Labs!
>
> All very good points, but the ways in which a caliper deflects under
> load aren't the issue here. There's a claim here that there's an arm
> twisting under no load that's a result of a design feature. There
> has been no credible evidence to support this, only optical tricks.
>
er, you said:
"If there is something special about that second pivot, which
differentiates the caliper as front or rear by making the arm twist one
way or another, then the pad attached to it will be moving fore and aft
relative to the other pad as the caliper opens and closes."
and my pics just so happen to show precisely that. but now you're
back-tracking saying it's some kind of deception? that's ridiculous.
|
| | | | | | |
Date: 01 Nov 2007 14:08:07
From: James Thomson
Subject: Re: Mount front brakes on rear?
|
>> What should I be measuring?
"jim beam" <spamvortex@bad.example.net > a écrit:
> distance between the front tips of the brake pads with the caliper
> open vs. caliper closed, and for the rear tips, open vs closed. when
> open, the front tips are further apart than the rears. when closed,
> the front tips are closer than the rears. [front caliper]
I'm using the moulding seam of the brake block at the point it touches the
holder as a reference point on the Ultegra 6500 brakes, and (in the absence
of a convenient moulding mark) trying to pick a consistent point on the
Centaur pad holder. The measurements are repeatable to within about 1mm, and
I can't detect any sign of the effect you say is there.
James Thomson
|
| | | | | | | |
Date: 01 Nov 2007 14:45:20
From: _
Subject: Re: Mount front brakes on rear?
|
On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
>>> What should I be measuring?
>
> "jim beam" <spamvortex@bad.example.net> a écrit:
>
>> distance between the front tips of the brake pads with the caliper
>> open vs. caliper closed, and for the rear tips, open vs closed. when
>> open, the front tips are further apart than the rears. when closed,
>> the front tips are closer than the rears. [front caliper]
>
> I'm using the moulding seam of the brake block at the point it touches the
> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> of a convenient moulding mark) trying to pick a consistent point on the
> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> I can't detect any sign of the effect you say is there.
>
> James Thomson
Either beam's bushings are worn or the arms are loose on the pivots - that
was already pointed out. It's impossible for an arm to pivot on a
cylindrical bushing and change the axis of rotation without another pivot
(which is, in essemce, what beamboy is claiming).
|
| | | | | |
Date: 31 Oct 2007 22:35:17
From: _
Subject: Re: Mount front brakes on rear?
|
On Wed, 31 Oct 2007 15:33:32 +0100, James Thomson wrote:
> "jim beam" <spamvortex@bad.example.net> a écrit:
>
>>>>> shimano & campy dual pivot brake calipers have a pivot action that
>>>>> increases toe on the pad
>>>>> as the caliper closes. [easily observed for yourself if you
>>>>> have the caliper in your hand - simply squeeze and note
>>>>> how the relative angles of the pads change as the lever
>>>>> arms move through their arc.]
>
>> since you presumably have these things laying about your store,
>> new in box, why not dig out both brake calipers and measuring
>> calipers and measure what i describe?
>
> What should I be measuring? I have new (previous generation) Campag Centaur
> and Shimano Ultegra calipers here on my desk, and I can't see or measure any
> change in angle between the pads relative to the plane of the rim. In fact I
> can't readily see how that would be possible, as the pivot of one arm is
> co-axial with the brake bolt in each case (and that's true of all dual-pivot
> brakes I've seen).
>
Exactly - as another poster has said, it is geometrically impossible to
produce two degrees of freedom with one pivot axis.
|
| | | | | | |
Date: 31 Oct 2007 20:37:23
From: jim beam
Subject: Re: Mount front brakes on rear?
|
_ wrote:
> On Wed, 31 Oct 2007 15:33:32 +0100, James Thomson wrote:
>
>> "jim beam" <spamvortex@bad.example.net> a �crit:
>>
>>>>>> shimano & campy dual pivot brake calipers have a pivot action that
>>>>>> increases toe on the pad
>>>>>> as the caliper closes. [easily observed for yourself if you
>>>>>> have the caliper in your hand - simply squeeze and note
>>>>>> how the relative angles of the pads change as the lever
>>>>>> arms move through their arc.]
>>> since you presumably have these things laying about your store,
>>> new in box, why not dig out both brake calipers and measuring
>>> calipers and measure what i describe?
>> What should I be measuring? I have new (previous generation) Campag Centaur
>> and Shimano Ultegra calipers here on my desk, and I can't see or measure any
>> change in angle between the pads relative to the plane of the rim. In fact I
>> can't readily see how that would be possible, as the pivot of one arm is
>> co-axial with the brake bolt in each case (and that's true of all dual-pivot
>> brakes I've seen).
>>
>
> Exactly - as another poster has said, it is geometrically impossible to
> produce two degrees of freedom with one pivot axis.
and with a _dual pivot_ brake caliper you have, wait for it, _two_ pivot
axes! now, that gives /how/ many degrees of freedom?
|
| | | | | | | |
Date: 01 Nov 2007 08:27:05
From: _
Subject: Re: Mount front brakes on rear?
|
On Wed, 31 Oct 2007 20:37:23 -0700, jim beam wrote:
> _ wrote:
>> On Wed, 31 Oct 2007 15:33:32 +0100, James Thomson wrote:
>>
>>> "jim beam" <spamvortex@bad.example.net> a �crit:
>>>
>>>>>>> shimano & campy dual pivot brake calipers have a pivot action that
>>>>>>> increases toe on the pad
>>>>>>> as the caliper closes. [easily observed for yourself if you
>>>>>>> have the caliper in your hand - simply squeeze and note
>>>>>>> how the relative angles of the pads change as the lever
>>>>>>> arms move through their arc.]
>>>> since you presumably have these things laying about your store,
>>>> new in box, why not dig out both brake calipers and measuring
>>>> calipers and measure what i describe?
>>> What should I be measuring? I have new (previous generation) Campag Centaur
>>> and Shimano Ultegra calipers here on my desk, and I can't see or measure any
>>> change in angle between the pads relative to the plane of the rim. In fact I
>>> can't readily see how that would be possible, as the pivot of one arm is
>>> co-axial with the brake bolt in each case (and that's true of all dual-pivot
>>> brakes I've seen).
>>>
>>
>> Exactly - as another poster has said, it is geometrically impossible to
>> produce two degrees of freedom with one pivot axis.
>
> and with a _dual pivot_ brake caliper you have, wait for it, _two_ pivot
> axes! now, that gives /how/ many degrees of freedom?
One for each arm. You were saying that each arm changes angle as it
pivots; as another poster has stated, that is geometrically impossible with
a single axis.
Time to weasle again, beamboy.
|
| | | | | | | | |
Date: 01 Nov 2007 06:03:01
From: jim beam
Subject: Re: Mount front brakes on rear?
|
_ wrote:
> On Wed, 31 Oct 2007 20:37:23 -0700, jim beam wrote:
>
>> _ wrote:
>>> On Wed, 31 Oct 2007 15:33:32 +0100, James Thomson wrote:
>>>
>>>> "jim beam" <spamvortex@bad.example.net> a �crit:
>>>>
>>>>>>>> shimano & campy dual pivot brake calipers have a pivot action that
>>>>>>>> increases toe on the pad
>>>>>>>> as the caliper closes. [easily observed for yourself if you
>>>>>>>> have the caliper in your hand - simply squeeze and note
>>>>>>>> how the relative angles of the pads change as the lever
>>>>>>>> arms move through their arc.]
>>>>> since you presumably have these things laying about your store,
>>>>> new in box, why not dig out both brake calipers and measuring
>>>>> calipers and measure what i describe?
>>>> What should I be measuring? I have new (previous generation) Campag Centaur
>>>> and Shimano Ultegra calipers here on my desk, and I can't see or measure any
>>>> change in angle between the pads relative to the plane of the rim. In fact I
>>>> can't readily see how that would be possible, as the pivot of one arm is
>>>> co-axial with the brake bolt in each case (and that's true of all dual-pivot
>>>> brakes I've seen).
>>>>
>>> Exactly - as another poster has said, it is geometrically impossible to
>>> produce two degrees of freedom with one pivot axis.
>> and with a _dual pivot_ brake caliper you have, wait for it, _two_ pivot
>> axes! now, that gives /how/ many degrees of freedom?
>
> One for each arm. You were saying that each arm changes angle as it
> pivots; as another poster has stated, that is geometrically impossible with
> a single axis.
>
> Time to weasle again, beamboy.
1. you need to find a better math teacher.
2. go find yourself a dual pivot caliper and observe for yourself.
|
| |
Date: 29 Oct 2007 09:33:12
From:
Subject: Re: Mount front brakes on rear?
|
On Oct 28, 6:48 pm, zarf...@gmail.com wrote:
> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> my front wheel. My rear caliper is kinda corroded, and I was
> considering mounting another front caliper on the rear wheel... Is
> this a good idea?
If you have an old bolt for the rear, you can disassemble the brake
and replace the longer front bolt with a shorter one required for the
rear. I believe this is even easier to do with dual pivot sidepulls
than the old style single pivots, but it's been a while since I've
taken one of these apart.
|
| | |
Date: 30 Oct 2007 12:55:20
From: _
Subject: Re: Mount front brakes on rear?
|
On Mon, 29 Oct 2007 09:33:12 -0700, peteymills@hotmail.com wrote:
> On Oct 28, 6:48 pm, zarf...@gmail.com wrote:
>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>> my front wheel. My rear caliper is kinda corroded, and I was
>> considering mounting another front caliper on the rear wheel... Is
>> this a good idea?
>
> If you have an old bolt for the rear, you can disassemble the brake
> and replace the longer front bolt with a shorter one required for the
> rear. I believe this is even easier to do with dual pivot sidepulls
> than the old style single pivots, but it's been a while since I've
> taken one of these apart.
Or run a die down the longer bolt and cut the excess off.
|
| | | |
Date: 30 Oct 2007 10:09:43
From: Kerry Montgomery
Subject: Re: Mount front brakes on rear?
|
"_" <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com > wrote in message
news:ax344p6chxxu.vm8hk1s7uucy$.dlg@40tude.net...
> On Mon, 29 Oct 2007 09:33:12 -0700, peteymills@hotmail.com wrote:
>
>> On Oct 28, 6:48 pm, zarf...@gmail.com wrote:
>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>> my front wheel. My rear caliper is kinda corroded, and I was
>>> considering mounting another front caliper on the rear wheel... Is
>>> this a good idea?
>>
>> If you have an old bolt for the rear, you can disassemble the brake
>> and replace the longer front bolt with a shorter one required for the
>> rear. I believe this is even easier to do with dual pivot sidepulls
>> than the old style single pivots, but it's been a while since I've
>> taken one of these apart.
>
> Or run a die down the longer bolt and cut the excess off.
But then you'd have cut threads instead of the superior rolled threads
(vastly superior if they're Italian rolled threads).
Kerry
|
| | | | |
Date: 31 Oct 2007 13:57:14
From: _
Subject: Re: Mount front brakes on rear?
|
On Tue, 30 Oct 2007 10:09:43 -0700, Kerry Montgomery wrote:
> "_" <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com> wrote in message
> news:ax344p6chxxu.vm8hk1s7uucy$.dlg@40tude.net...
>> On Mon, 29 Oct 2007 09:33:12 -0700, peteymills@hotmail.com wrote:
>>
>>> On Oct 28, 6:48 pm, zarf...@gmail.com wrote:
>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>> considering mounting another front caliper on the rear wheel... Is
>>>> this a good idea?
>>>
>>> If you have an old bolt for the rear, you can disassemble the brake
>>> and replace the longer front bolt with a shorter one required for the
>>> rear. I believe this is even easier to do with dual pivot sidepulls
>>> than the old style single pivots, but it's been a while since I've
>>> taken one of these apart.
>>
>> Or run a die down the longer bolt and cut the excess off.
>
> But then you'd have cut threads instead of the superior rolled threads
> (vastly superior if they're Italian rolled threads).
> Kerry
For the strength required of a brake bolt, it makes no difference.
|
| | | | | |
Date: 31 Oct 2007 16:56:13
From: Michael Press
Subject: Re: Mount front brakes on rear?
|
In article <1pau2vo0ooci.oczfdfwk7ium.dlg@40tude.net >,
_ <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com > wrote:
> On Tue, 30 Oct 2007 10:09:43 -0700, Kerry Montgomery wrote:
>
> > "_" <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com> wrote in message
> > news:ax344p6chxxu.vm8hk1s7uucy$.dlg@40tude.net...
> >> On Mon, 29 Oct 2007 09:33:12 -0700, peteymills@hotmail.com wrote:
> >>
> >>> On Oct 28, 6:48 pm, zarf...@gmail.com wrote:
> >>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> >>>> my front wheel. My rear caliper is kinda corroded, and I was
> >>>> considering mounting another front caliper on the rear wheel... Is
> >>>> this a good idea?
> >>>
> >>> If you have an old bolt for the rear, you can disassemble the brake
> >>> and replace the longer front bolt with a shorter one required for the
> >>> rear. I believe this is even easier to do with dual pivot sidepulls
> >>> than the old style single pivots, but it's been a while since I've
> >>> taken one of these apart.
> >>
> >> Or run a die down the longer bolt and cut the excess off.
> >
> > But then you'd have cut threads instead of the superior rolled threads
> > (vastly superior if they're Italian rolled threads).
> > Kerry
>
> For the strength required of a brake bolt, it makes no difference.
Do you skip messages that are in jim beam debate threads?
--
Michael Press
|
| | | | | | |
Date: 02 Nov 2007 13:38:45
From: _
Subject: Re: Mount front brakes on rear?
|
On Wed, 31 Oct 2007 16:56:13 -0700, Michael Press wrote:
> In article <1pau2vo0ooci.oczfdfwk7ium.dlg@40tude.net>,
> _ <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com> wrote:
>
>> On Tue, 30 Oct 2007 10:09:43 -0700, Kerry Montgomery wrote:
>>
>>> "_" <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com> wrote in message
>>> news:ax344p6chxxu.vm8hk1s7uucy$.dlg@40tude.net...
>>>> On Mon, 29 Oct 2007 09:33:12 -0700, peteymills@hotmail.com wrote:
>>>>
>>>>> On Oct 28, 6:48 pm, zarf...@gmail.com wrote:
>>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>>>>>> my front wheel. My rear caliper is kinda corroded, and I was
>>>>>> considering mounting another front caliper on the rear wheel... Is
>>>>>> this a good idea?
>>>>>
>>>>> If you have an old bolt for the rear, you can disassemble the brake
>>>>> and replace the longer front bolt with a shorter one required for the
>>>>> rear. I believe this is even easier to do with dual pivot sidepulls
>>>>> than the old style single pivots, but it's been a while since I've
>>>>> taken one of these apart.
>>>>
>>>> Or run a die down the longer bolt and cut the excess off.
>>>
>>> But then you'd have cut threads instead of the superior rolled threads
>>> (vastly superior if they're Italian rolled threads).
>>> Kerry
>>
>> For the strength required of a brake bolt, it makes no difference.
>
> Do you skip messages that are in jim beam debate threads?
Who is "jim beam"?
|
| | | | | | | |
Date: 03 Nov 2007 05:19:25
From: Michael Press
Subject: Re: Mount front brakes on rear?
|
In article
<z62uybw4gxso.1ste875wxeb04$.dlg@40tude.net >,
_ <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com > wrote:
> On Wed, 31 Oct 2007 16:56:13 -0700, Michael Press wrote:
>
> > In article <1pau2vo0ooci.oczfdfwk7ium.dlg@40tude.net>,
> > _ <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com> wrote:
> >
> >> On Tue, 30 Oct 2007 10:09:43 -0700, Kerry Montgomery wrote:
> >>
> >>> "_" <jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com> wrote in message
> >>> news:ax344p6chxxu.vm8hk1s7uucy$.dlg@40tude.net...
> >>>> On Mon, 29 Oct 2007 09:33:12 -0700, peteymills@hotmail.com wrote:
> >>>>
> >>>>> On Oct 28, 6:48 pm, zarf...@gmail.com wrote:
> >>>>>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> >>>>>> my front wheel. My rear caliper is kinda corroded, and I was
> >>>>>> considering mounting another front caliper on the rear wheel... Is
> >>>>>> this a good idea?
> >>>>>
> >>>>> If you have an old bolt for the rear, you can disassemble the brake
> >>>>> and replace the longer front bolt with a shorter one required for the
> >>>>> rear. I believe this is even easier to do with dual pivot sidepulls
> >>>>> than the old style single pivots, but it's been a while since I've
> >>>>> taken one of these apart.
> >>>>
> >>>> Or run a die down the longer bolt and cut the excess off.
> >>>
> >>> But then you'd have cut threads instead of the superior rolled threads
> >>> (vastly superior if they're Italian rolled threads).
> >>> Kerry
> >>
> >> For the strength required of a brake bolt, it makes no difference.
> >
> > Do you skip messages that are in jim beam debate threads?
>
> Who is "jim beam"?
Accounts for you being trolled on the
great brake bolt thread controversy.
--
Michael Press
|
| | | | | | | |
Date: 02 Nov 2007 18:43:36
From: Tom Sherman
Subject: Re: Mount front brakes on rear?
|
J. Taylor wrote:
>
> Who is "jim beam"?
I think its a bot.
--
Tom Sherman - Holstein-Friesland Bovinia
When did ignorance of biology become a "family value"?
|
| | |
Date: 29 Oct 2007 19:55:03
From: jim beam
Subject: Re: Mount front brakes on rear?
|
peteymills@hotmail.com wrote:
> On Oct 28, 6:48 pm, zarf...@gmail.com wrote:
>> Nashbar has a good deal on ultegra brake calipers; I mounted them on
>> my front wheel. My rear caliper is kinda corroded, and I was
>> considering mounting another front caliper on the rear wheel... Is
>> this a good idea?
>
> If you have an old bolt for the rear, you can disassemble the brake
> and replace the longer front bolt with a shorter one required for the
> rear.
not with dual pivot - you run into the toe problem i described in my
other post.
> I believe this is even easier to do with dual pivot sidepulls
> than the old style single pivots, but it's been a while since I've
> taken one of these apart.
>
|
| |
Date: 28 Oct 2007 20:01:29
From: jim beam
Subject: Re: Mount front brakes on rear?
|
zarfus1@gmail.com wrote:
> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> my front wheel. My rear caliper is kinda corroded, and I was
> considering mounting another front caliper on the rear wheel... Is
> this a good idea?
>
as pointed out by others, the bolt length thing is not a big deal.
however, you need to be aware that shimano & campy dual pivot brake
calipers have a pivot action that increases toe on the pad as the
caliper closes. [easily observed for yourself if you have the caliper
in your hand - simply squeeze and note how the relative angles of the
pads change as the lever arms move through their arc.] if a front
caliper is used on the rear, the toe is towards the rear of the pads,
not the front, relative to rim direction.
will you notice any effect in practice? maybe some brake squeal, but
probably not. is it correct in theory? no. and iirc, there's a
warning in the shimano literature to the effect that each caliper is
specific to front or rear application and should not be interchanged.
|
| |
Date: 28 Oct 2007 14:36:41
From:
Subject: Re: Mount front brakes on rear?
|
On Oct 28, 5:22 pm, landotter <landot...@gmail.com > wrote:
> On Oct 28, 4:04 pm, Stephen Bauman <sbau...@abt.net> wrote:
>
> > On Sun, 28 Oct 2007 11:28:58 -0700, zarfus1 wrote:
>
> > > Is it ok to do this with a carbon chainstay?
>
> > Aren't rear brakes usually mounted on the seat stays?
>
> I'll take Brake Bridge for $200, Alex.
oops yes seat stays.
|
| |
Date: 28 Oct 2007 14:22:53
From: landotter
Subject: Re: Mount front brakes on rear?
|
On Oct 28, 4:04 pm, Stephen Bauman <sbau...@abt.net > wrote:
> On Sun, 28 Oct 2007 11:28:58 -0700, zarfus1 wrote:
>
> > Is it ok to do this with a carbon chainstay?
>
> Aren't rear brakes usually mounted on the seat stays?
>
I'll take Brake Bridge for $200, Alex.
|
| |
Date: 28 Oct 2007 15:08:09
From: A Muzi
Subject: Re: Mount front brakes on rear?
|
zarfus1@gmail.com wrote:
> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> my front wheel. My rear caliper is kinda corroded, and I was
> considering mounting another front caliper on the rear wheel... Is
> this a good idea?
A front is a rear with the brake shoes reversed. Bolt length varies so
if you can, you may. Check the mounting format.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| |
Date: 28 Oct 2007 16:04:38
From: Stephen Bauman
Subject: Re: Mount front brakes on rear?
|
On Sun, 28 Oct 2007 11:28:58 -0700, zarfus1 wrote:
>
> Is it ok to do this with a carbon chainstay?
Aren't rear brakes usually mounted on the seat stays?
Stephen Bauman
|
| |
Date: 28 Oct 2007 11:45:45
From: landotter
Subject: Re: Mount front brakes on rear?
|
On Oct 28, 1:28 pm, zarf...@gmail.com wrote:
> On Oct 28, 2:22 pm, landotter <landot...@gmail.com> wrote:
>
> > On Oct 28, 12:48 pm, zarf...@gmail.com wrote:
>
> > > Nashbar has a good deal on ultegra brake calipers; I mounted them on
> > > my front wheel. My rear caliper is kinda corroded, and I was
> > > considering mounting another front caliper on the rear wheel... Is
> > > this a good idea?
>
> > It should work fine if you use a washer and a regular nut instead of
> > the recessed one that comes with it.
>
> Is it ok to do this with a carbon chainstay?
I don't see why not.
|
| |
Date: 28 Oct 2007 11:28:58
From:
Subject: Re: Mount front brakes on rear?
|
On Oct 28, 2:22 pm, landotter <landot...@gmail.com > wrote:
> On Oct 28, 12:48 pm, zarf...@gmail.com wrote:
>
> > Nashbar has a good deal on ultegra brake calipers; I mounted them on
> > my front wheel. My rear caliper is kinda corroded, and I was
> > considering mounting another front caliper on the rear wheel... Is
> > this a good idea?
>
> It should work fine if you use a washer and a regular nut instead of
> the recessed one that comes with it.
Is it ok to do this with a carbon chainstay?
|
| |
Date: 28 Oct 2007 11:22:43
From: landotter
Subject: Re: Mount front brakes on rear?
|
On Oct 28, 12:48 pm, zarf...@gmail.com wrote:
> Nashbar has a good deal on ultegra brake calipers; I mounted them on
> my front wheel. My rear caliper is kinda corroded, and I was
> considering mounting another front caliper on the rear wheel... Is
> this a good idea?
It should work fine if you use a washer and a regular nut instead of
the recessed one that comes with it.
|
|
