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Main
Date: 09 Nov 2007 16:37:32
From: Jim Flom
Subject: rear rim seems to rub
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My rear rim seems to rub on a brake pad when I am standing on the pedals on
steep climbs. At least that's what I THINK it is. Off the bike, everything
appears trued up well with good clearance. It's my 1998 Raleigh R500 7005
alu frame with oversized tubes.
Any theories? Any suggestions?
--
JF
"A really great man is known by three signs,--generosity in the design,
humanity in the execution, and moderation in success."
- Karl Otto von Schonhausen Bismarck
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Date: 14 Nov 2007 07:49:31
From: Joe Riel
Subject: Re: rear rim seems to rub
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Ben C <spamspam@spam.eggs > writes:
> On 2007-11-14, Joe Riel <joer@san.rr.com> wrote:
> [...]
>> Here's a simple, possibly relevant, thought experiment. Start with an
>> auto disk with a single piston. The caliper floats so that both pads,
>> the moving one and the fixed one on the opposing side, apply opposing
>> forces of equal magnitude. Add a second, identical piston, on the
>> same side. The mechanical advantage doubles (assume all pistons are
>> driven by a common master cylinder).
>
>> What if, instead, the second piston is installed on the other side of
>> the disk? In that case, the mechanical advantage is equivalent to
>> that of a single piston.
>
> Isn't it just the same? It doesn't matter which side of the disk either
> piston is.
But it does. For any fluid pressure, P, the force exerted by each
piston, whether on the same side or opposing sides, is F=P*A, where A
is the area of the piston's slave cylinder. But with both pistons on
the same side, then the fixed pads on the opposing side also exert a
force F, so the normal force on each side is 2*F.
> You've still doubled the area that the fluid is pushing against at the
> slave end.
Another way to think about is strictly in terms of piston travel.
Adding a second piston to the same side causes the master cylinder to
must twice as far (pump twice the fluid) for the same slave cylinder
stroke. The mechanical advantage has doubled.
Adding the second piston to the opposing side doesn't change the
stroke of the master cylinder, each slave cylinder has to move
half as far. So the mechanical advantage is the same as with one
slave cylinder and a fixed opposing pad.
>> pistons on one side, one opposing. The mechanical advantage is twice
>> that of the single piston, but the single piston does no work;
>> instead, after it makes contact with the disk, it will be forced back
>> by the two on the other side (as the caliper assembly floats).
>> Assuming it hits a stop, we are then in a situation identical to two
>> pistons on one side.
>
> Then I think you just get even more leverage (so three times the
> original one-piston set-up), and the brake should work fine.
With n1 pistons on one side and n2 on the other, the mechanical
advantage is max(n1,n2), and unless n1=n2, only one side does any
effective work (assuming pistons can compress to a stop, otherwise
there is no braking force).
--
Joe Riel
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Date: 14 Nov 2007 16:19:42
From: Ben C
Subject: Re: rear rim seems to rub
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On 2007-11-14, Joe Riel <joer@san.rr.com > wrote:
> Ben C <spamspam@spam.eggs> writes:
>
>> On 2007-11-14, Joe Riel <joer@san.rr.com> wrote:
>> [...]
>>> Here's a simple, possibly relevant, thought experiment. Start with an
>>> auto disk with a single piston. The caliper floats so that both pads,
>>> the moving one and the fixed one on the opposing side, apply opposing
>>> forces of equal magnitude. Add a second, identical piston, on the
>>> same side. The mechanical advantage doubles (assume all pistons are
>>> driven by a common master cylinder).
>>
>>> What if, instead, the second piston is installed on the other side of
>>> the disk? In that case, the mechanical advantage is equivalent to
>>> that of a single piston.
>>
>> Isn't it just the same? It doesn't matter which side of the disk either
>> piston is.
[...]
> Another way to think about is strictly in terms of piston travel.
Yes, that's the one I find easiest. F*d must be the same both ends. Make
d shorter on the output and F on the output must be correspondingly
bigger.
> Adding a second piston to the same side causes the master cylinder to
> must twice as far (pump twice the fluid) for the same slave cylinder
> stroke. The mechanical advantage has doubled.
>
> Adding the second piston to the opposing side doesn't change the
> stroke of the master cylinder, each slave cylinder has to move
> half as far.
OK, yes.
Suppose the total amount you squeeze the pads by is 4mm, with the left
pad and right pad each compressing by 2mm.
With both pistons on one side, each piston moves 4mm in its own bore,
moving 2mm relative to the disk and another 2mm relative to the caliper.
The far side of the caliper moves -2mm relative to the disk.
With one piston on each side, each piston extends 2mm relative to the
caliper (one does 2mm and the other -2mm) and the caliper stays where it
is.
So with both pistons on the same side, you need to pump in twice as much
fluid to get the 4mm total displacement
You would therefore require double the stroke on the master piston,
which means twice as much force over those 4mm.
So you're right: twice the mechanical advantage.
Two pistons on one side is like using a fatter piston. One piston on
each side is just like using a longer one with the same bore (i.e makes
no difference to mechanical advantage).
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Date: 14 Nov 2007 19:56:44
From: jim beam
Subject: Re: rear rim seems to rub
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Ben C wrote:
> On 2007-11-14, Joe Riel <joer@san.rr.com> wrote:
>> Ben C <spamspam@spam.eggs> writes:
>>
>>> On 2007-11-14, Joe Riel <joer@san.rr.com> wrote:
>>> [...]
>>>> Here's a simple, possibly relevant, thought experiment. Start with an
>>>> auto disk with a single piston. The caliper floats so that both pads,
>>>> the moving one and the fixed one on the opposing side, apply opposing
>>>> forces of equal magnitude. Add a second, identical piston, on the
>>>> same side. The mechanical advantage doubles (assume all pistons are
>>>> driven by a common master cylinder).
>>>> What if, instead, the second piston is installed on the other side of
>>>> the disk? In that case, the mechanical advantage is equivalent to
>>>> that of a single piston.
>>> Isn't it just the same? It doesn't matter which side of the disk either
>>> piston is.
> [...]
>> Another way to think about is strictly in terms of piston travel.
>
> Yes, that's the one I find easiest. F*d must be the same both ends. Make
> d shorter on the output and F on the output must be correspondingly
> bigger.
>
>> Adding a second piston to the same side causes the master cylinder to
>> must twice as far (pump twice the fluid) for the same slave cylinder
>> stroke. The mechanical advantage has doubled.
>>
>> Adding the second piston to the opposing side doesn't change the
>> stroke of the master cylinder, each slave cylinder has to move
>> half as far.
>
> OK, yes.
>
> Suppose the total amount you squeeze the pads by is 4mm, with the left
> pad and right pad each compressing by 2mm.
>
> With both pistons on one side, each piston moves 4mm in its own bore,
> moving 2mm relative to the disk and another 2mm relative to the caliper.
> The far side of the caliper moves -2mm relative to the disk.
>
> With one piston on each side, each piston extends 2mm relative to the
> caliper (one does 2mm and the other -2mm) and the caliper stays where it
> is.
>
> So with both pistons on the same side, you need to pump in twice as much
> fluid to get the 4mm total displacement
>
> You would therefore require double the stroke on the master piston,
> which means twice as much force over those 4mm.
>
> So you're right: twice the mechanical advantage.
>
> Two pistons on one side is like using a fatter piston.
yes. and two pistons on either side.
> One piston on
> each side is just like using a longer one with the same bore (i.e makes
> no difference to mechanical advantage).
see above, if the caliper or disk floats.
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Date: 13 Nov 2007 21:01:45
From: Joe Riel
Subject: Re: rear rim seems to rub
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jim beam <spamvortex@bad.example.net > writes:
> Joe Riel wrote:
>> The force of the fixed
>> piston comes through the body of the caliper assembly. If the caliper
>> has just one piston, the caliper is designed to float relative to the
>> disk (the float isn't completely free, however, the force required to
>> move the caliper body is negligible compared to that applied to the
>> disk).
>
> that's true of sliding caliper disk brakes found in automotive
> applications, but i've never seen one like that for a bike. avid use
> a fixed caliper and the movement is accommodated solely by flexing of
> the actual disk.
Yes, I was referring to an automotive disk brake. A disk for a bicycle
can be thin enough to flex and provide the needed float.
>> On a rim brake, it is clear that the net lateral force applied to the
>> rim must be zero, otherwise the rim will move, and continue to move,
>> laterally.
>
> indeed. and this is observed if a dual-pivot brake caliper is mounted
> off center. all this stuff about "100N on one side and 200N on the
> other" is gross failure to understand the fundamentals.
Here's a simple, possibly relevant, thought experiment. Start with an
auto disk with a single piston. The caliper floats so that both pads,
the moving one and the fixed one on the opposing side, apply opposing
forces of equal magnitude. Add a second, identical piston, on the
same side. The mechanical advantage doubles (assume all pistons are
driven by a common master cylinder). What if, instead, the second
piston is installed on the other side of the disk? In that case, the
mechanical advantage is equivalent to that of a single piston.
Now for the fun part. Install a third piston, so there are two
pistons on one side, one opposing. The mechanical advantage is twice
that of the single piston, but the single piston does no work;
instead, after it makes contact with the disk, it will be forced back
by the two on the other side (as the caliper assembly floats).
Assuming it hits a stop, we are then in a situation identical to two
pistons on one side.
--
Joe Riel
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Date: 14 Nov 2007 06:06:30
From: jim beam
Subject: Re: rear rim seems to rub
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Joe Riel wrote:
> jim beam <spamvortex@bad.example.net> writes:
>
>> Joe Riel wrote:
>
>>> The force of the fixed
>>> piston comes through the body of the caliper assembly. If the caliper
>>> has just one piston, the caliper is designed to float relative to the
>>> disk (the float isn't completely free, however, the force required to
>>> move the caliper body is negligible compared to that applied to the
>>> disk).
>> that's true of sliding caliper disk brakes found in automotive
>> applications, but i've never seen one like that for a bike. avid use
>> a fixed caliper and the movement is accommodated solely by flexing of
>> the actual disk.
>
> Yes, I was referring to an automotive disk brake. A disk for a bicycle
> can be thin enough to flex and provide the needed float.
>
>>> On a rim brake, it is clear that the net lateral force applied to the
>>> rim must be zero, otherwise the rim will move, and continue to move,
>>> laterally.
>> indeed. and this is observed if a dual-pivot brake caliper is mounted
>> off center. all this stuff about "100N on one side and 200N on the
>> other" is gross failure to understand the fundamentals.
>
> Here's a simple, possibly relevant, thought experiment. Start with an
> auto disk with a single piston. The caliper floats so that both pads,
> the moving one and the fixed one on the opposing side, apply opposing
> forces of equal magnitude. Add a second, identical piston, on the
> same side. The mechanical advantage doubles (assume all pistons are
> driven by a common master cylinder). What if, instead, the second
> piston is installed on the other side of the disk? In that case, the
> mechanical advantage is equivalent to that of a single piston.
>
> Now for the fun part. Install a third piston, so there are two
> pistons on one side, one opposing. The mechanical advantage is twice
> that of the single piston, but the single piston does no work;
> instead, after it makes contact with the disk, it will be forced back
> by the two on the other side (as the caliper assembly floats).
> Assuming it hits a stop, we are then in a situation identical to two
> pistons on one side.
>
>
that's a good thought experiment! indeed - the single piston will be
forced back. this is effectively the same as the bike caliper with two
different arm leverage ratios except that the y-arm can't move backwards
because of the application of brake pressure.
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Date: 14 Nov 2007 03:11:38
From: Ben C
Subject: Re: rear rim seems to rub
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On 2007-11-14, Joe Riel <joer@san.rr.com > wrote:
[...]
> Here's a simple, possibly relevant, thought experiment. Start with an
> auto disk with a single piston. The caliper floats so that both pads,
> the moving one and the fixed one on the opposing side, apply opposing
> forces of equal magnitude. Add a second, identical piston, on the
> same side. The mechanical advantage doubles (assume all pistons are
> driven by a common master cylinder).
> What if, instead, the second piston is installed on the other side of
> the disk? In that case, the mechanical advantage is equivalent to
> that of a single piston.
Isn't it just the same? It doesn't matter which side of the disk either
piston is.
You've still doubled the area that the fluid is pushing against at the
slave end.
> Now for the fun part. Install a third piston, so there are two
> pistons on one side, one opposing. The mechanical advantage is twice
> that of the single piston, but the single piston does no work;
> instead, after it makes contact with the disk, it will be forced back
> by the two on the other side (as the caliper assembly floats).
> Assuming it hits a stop, we are then in a situation identical to two
> pistons on one side.
Then I think you just get even more leverage (so three times the
original one-piston set-up), and the brake should work fine.
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Date: 13 Nov 2007 13:22:06
From: Joe Riel
Subject: Re: rear rim seems to rub
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jobst.brandt@stanfordalumni.org writes:
> Dual pivot calipers cannot float, that being one of their weaknesses;
> not being able to track a wobbling rim. The two arms of the caliper
> are bound to articulate together equally at all times. Therefore the
> scenario of the floating rim is meaningless. By pushing either pad
> inward, notice mirror image motion of the opposite one.
That isn't precisely correct. It is possible to push one arm in and
not have the other track. However, if both arms are held together and
torque applied to them (such as would happen with a wobbling rim), the
torque is transferred to the mounting bolt, through the fixed "half
arm". It isn't clear that that would prevent tracking, since I'd
expect the mounting bolt to turn. The braking wouldn't be
particularly nice. I suspect that the bigger problem is that with the
higher gain it isn't possible to get enough to clearance for a wobbly
rim *and* still have useful lever travel.
With a single pivot, only friction torque is applied to the mounting
bolt, through the bushing, and that isn't enough to cause the bolt to
rotate nor to interfere with braking.
> Trying to measure effective caliper arm lengths is illusive. Measure
> relative travel as I suggested. That's how I arrived at my ratios.
Measuring the relative travel is the straightforward technique.
--
Joe Riel
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Date: 13 Nov 2007 20:15:22
From: jim beam
Subject: Re: rear rim seems to rub
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Joe Riel wrote:
> jobst.brandt@stanfordalumni.org writes:
>
>> Dual pivot calipers cannot float, that being one of their weaknesses;
>> not being able to track a wobbling rim. The two arms of the caliper
>> are bound to articulate together equally at all times. Therefore the
>> scenario of the floating rim is meaningless. By pushing either pad
>> inward, notice mirror image motion of the opposite one.
>
> That isn't precisely correct. It is possible to push one arm in and
> not have the other track. However, if both arms are held together and
> torque applied to them (such as would happen with a wobbling rim), the
> torque is transferred to the mounting bolt, through the fixed "half
> arm". It isn't clear that that would prevent tracking, since I'd
> expect the mounting bolt to turn. The braking wouldn't be
> particularly nice. I suspect that the bigger problem is that with the
> higher gain it isn't possible to get enough to clearance for a wobbly
> rim *and* still have useful lever travel.
that is indeed true. but in a world where we have deeper rims that take
more before they bend, that can be less of an issue.
>
> With a single pivot, only friction torque is applied to the mounting
> bolt, through the bushing, and that isn't enough to cause the bolt to
> rotate nor to interfere with braking.
>
>> Trying to measure effective caliper arm lengths is illusive. Measure
>> relative travel as I suggested. That's how I arrived at my ratios.
>
> Measuring the relative travel is the straightforward technique.
>
but not terribly accurate. measuring the gap between pad and rim, if
you're doing it on the bike, is full of error.
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Date: 13 Nov 2007 07:42:56
From: Joe Riel
Subject: Re: rear rim seems to rub
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jim beam <spamvortex@bad.example.net > writes:
>> One more time: how do you propose that the Y arm with 1:1 ratio
>> between lever and pad supports 100N at the cable and 200N at the pad as
>> you propose? I've asked this several times now, but you have yet to
>> give an answer other than waving your hands about the floating rim. The
>> floating rim is not an answer - it only deals with how the 200N gets to
>> the pad, not how the lever is able to support it.
>
> disk brake!!! check it out.
Both pads on a disk brake, regardless that it has a piston on just one
side, apply a force of the same magnitude. The force of the fixed
piston comes through the body of the caliper assembly. If the caliper
has just one piston, the caliper is designed to float relative to the
disk (the float isn't completely free, however, the force required to
move the caliper body is negligible compared to that applied to the
disk).
On a rim brake, it is clear that the net lateral force applied to the
rim must be zero, otherwise the rim will move, and continue to move,
laterally.
--
Joe Riel
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Date: 13 Nov 2007 20:15:47
From: jim beam
Subject: Re: rear rim seems to rub
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Joe Riel wrote:
> jim beam <spamvortex@bad.example.net> writes:
>
>>> One more time: how do you propose that the Y arm with 1:1 ratio
>>> between lever and pad supports 100N at the cable and 200N at the pad as
>>> you propose? I've asked this several times now, but you have yet to
>>> give an answer other than waving your hands about the floating rim. The
>>> floating rim is not an answer - it only deals with how the 200N gets to
>>> the pad, not how the lever is able to support it.
>> disk brake!!! check it out.
>
> Both pads on a disk brake, regardless that it has a piston on just one
> side, apply a force of the same magnitude.
indeed.
> The force of the fixed
> piston comes through the body of the caliper assembly. If the caliper
> has just one piston, the caliper is designed to float relative to the
> disk (the float isn't completely free, however, the force required to
> move the caliper body is negligible compared to that applied to the
> disk).
that's true of sliding caliper disk brakes found in automotive
applications, but i've never seen one like that for a bike. avid use a
fixed caliper and the movement is accommodated solely by flexing of the
actual disk.
>
> On a rim brake, it is clear that the net lateral force applied to the
> rim must be zero, otherwise the rim will move, and continue to move,
> laterally.
indeed. and this is observed if a dual-pivot brake caliper is mounted
off center. all this stuff about "100N on one side and 200N on the
other" is gross failure to understand the fundamentals.
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Date: 10 Nov 2007 13:53:28
From: Joe Riel
Subject: Re: rear rim seems to rub
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jim beam <spamvortex@bad.example.net > writes:
> jobst.brandt@stanfordalumni.org wrote:
>> To assess the mechanical advantage of a dual pivot caliper, measure
>> the cable stroke and pad closure.
>
> that's inaccurate and pointless. the lever ratios are easy and much
> more accessible. maybe that's why you got it wrong?
>
>> The caliper has the same effect of
>> the centerpull with two arms, each twice as long as the pivot-to-pad
>> dimension, but there are two of them, each providing half the motion.
>
> doesn't matter - the rim effectively floats. one pad could be static
> for all it matters to mechanical advantage. indeed, avid mechanical
> disk brakes use this principle.
>
>> It was this geometric gimmick that led people to believe that hey were
>> twice as powerful grabbers as sidepull brakes of that time. It wasn't
>> so.
>
> maybe to people that didn't measure their lever ratios correctly.
I just measured my Campy Record dual pivots.
Lever throw : 1.5 in
Pad movement 0.3 in
ratio is 5:1.
--
Joe Riel
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Date: 10 Nov 2007 14:26:18
From: jim beam
Subject: Re: rear rim seems to rub
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Joe Riel wrote:
> jim beam <spamvortex@bad.example.net> writes:
>
>> jobst.brandt@stanfordalumni.org wrote:
>>> To assess the mechanical advantage of a dual pivot caliper, measure
>>> the cable stroke and pad closure.
>> that's inaccurate and pointless. the lever ratios are easy and much
>> more accessible. maybe that's why you got it wrong?
>>
>>> The caliper has the same effect of
>>> the centerpull with two arms, each twice as long as the pivot-to-pad
>>> dimension, but there are two of them, each providing half the motion.
>> doesn't matter - the rim effectively floats. one pad could be static
>> for all it matters to mechanical advantage. indeed, avid mechanical
>> disk brakes use this principle.
>>
>>> It was this geometric gimmick that led people to believe that hey were
>>> twice as powerful grabbers as sidepull brakes of that time. It wasn't
>>> so.
>> maybe to people that didn't measure their lever ratios correctly.
>
> I just measured my Campy Record dual pivots.
>
> Lever throw : 1.5 in
> Pad movement 0.3 in
>
> ratio is 5:1.
>
if we measure the lever ratios directly, we get:
1. brake lever is ~4:1,
2. caliper [single pivot shimano 600] is 51mm:55mm [center pivot to
center of cable mount:center pivot to center of the brake mount slot] ~1:1.
3. caliper [dual pivot dura-ace 7700] is ~62mm:31mm ["C" arm pivot to
center of cable mount:"C" arm pivot to the center of the brake mount
slot] ~2:1.
4. caliper ['98 record dual pivot] is ~68mm:42mm ["C" arm pivot to
center of cable mount:"C" arm pivot to the center of the brake mount
slot] ~1.6:1. <- as best as i can measure without stripping yet
another bike.
1*2 = 4:1
1*3 = 8:1
1*4 = 6.4:1
interestingly, the pivot offset arm on campy is shorter than shimano -
explains the slightly different ratio.
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Date: 11 Nov 2007 02:50:05
From: Luns Tee
Subject: Re: rear rim seems to rub
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In article <1K6dnc0ZrKGWravanZ2dnUVZ_vKunZ2d@speakeasy.net >,
jim beam <spamvortex@bad.example.net > wrote:
>2. caliper [single pivot shimano 600] is 51mm:55mm [center pivot to
>center of cable mount:center pivot to center of the brake mount slot] ~1:1.
That's not a meaningful measurement, though the mistake you're
making, you make twice such that it more or less cancels out.
The cable does not pull at a right angle from the line from pivot
to cable mount, nor does the pad press orthogonal to the other line
you're measuring on.
Unless you want to measure angles and include their cosines into
your ratio, the correct distances to measure are the distance from the
line the cable pulls along to the pivot, and the distance from the
line the pads press along to the pivot.
By dumb luck, the angles at both ends is about the same, so your
mistake on one end cancels itself out on the other.
>3. caliper [dual pivot dura-ace 7700] is ~62mm:31mm ["C" arm pivot to
>center of cable mount:"C" arm pivot to the center of the brake mount
>slot] ~2:1.
What you measure here is the ratio for one arm of the caliper,
not the caliper as a whole: the two aren't the same. If you want to
look at the ratio from from force perspective, note that there is a
coupling between the C and Y arm through the centering setscrew. The
ratio of cable tension to pad force is not 2:1 - you have to account
for force transferred through this coupling. If you want to look at the
ratio from a motion perspective, then you have to account for the motion
of the Y arm's pad, and more importantly, cable end.
The coupling between arms is there to ensure the pads move equal
distances (remain centered) as the caliper opens or closes. To see the
ratio of the caliper as a whole, consider a 1mm change of pad distance.
The centering linkage makes it so that each pad moves 1/2mm individually.
With a ratio of ~2:1, the C arm pulls 2* 1/2mm of cable, while
the Y arm with its ~1:1 ratio, pulls another 1*1/2mm of cable, for a total
of about 1.5mm. The ratio of the caliper as a whole is thus about 1.5:
this is the average of the individual arm ratios.
My measurements of a Shimano 105 BR5500 caliper give 64mm:34mm
or about 1.9:1 for the C arm, and 37mm:42mm or 0.9:1 for the Y arm. The
average of these is 1.4:1. With a 4:1 lever gives an overall ratio of
5.6:1.
-Luns
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Date: 10 Nov 2007 23:18:57
From: jim beam
Subject: Re: rear rim seems to rub
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Luns Tee wrote:
> In article <1K6dnc0ZrKGWravanZ2dnUVZ_vKunZ2d@speakeasy.net>,
> jim beam <spamvortex@bad.example.net> wrote:
>> 2. caliper [single pivot shimano 600] is 51mm:55mm [center pivot to
>> center of cable mount:center pivot to center of the brake mount slot] ~1:1.
>
> That's not a meaningful measurement, though the mistake you're
> making, you make twice such that it more or less cancels out.
>
> The cable does not pull at a right angle from the line from pivot
> to cable mount, nor does the pad press orthogonal to the other line
> you're measuring on.
> Unless you want to measure angles and include their cosines into
> your ratio, the correct distances to measure are the distance from the
> line the cable pulls along to the pivot, and the distance from the
> line the pads press along to the pivot.
>
> By dumb luck, the angles at both ends is about the same, so your
> mistake on one end cancels itself out on the other.
you think i hadn't thunk of that?
>
>> 3. caliper [dual pivot dura-ace 7700] is ~62mm:31mm ["C" arm pivot to
>> center of cable mount:"C" arm pivot to the center of the brake mount
>> slot] ~2:1.
>
>
> What you measure here is the ratio for one arm of the caliper,
> not the caliper as a whole: the two aren't the same. If you want to
> look at the ratio from from force perspective, note that there is a
> coupling between the C and Y arm through the centering setscrew. The
> ratio of cable tension to pad force is not 2:1 - you have to account
> for force transferred through this coupling. If you want to look at the
> ratio from a motion perspective, then you have to account for the motion
> of the Y arm's pad, and more importantly, cable end.
>
> The coupling between arms is there to ensure the pads move equal
> distances (remain centered) as the caliper opens or closes. To see the
> ratio of the caliper as a whole, consider a 1mm change of pad distance.
> The centering linkage makes it so that each pad moves 1/2mm individually.
>
> With a ratio of ~2:1, the C arm pulls 2* 1/2mm of cable, while
> the Y arm with its ~1:1 ratio, pulls another 1*1/2mm of cable, for a total
> of about 1.5mm. The ratio of the caliper as a whole is thus about 1.5:
> this is the average of the individual arm ratios.
>
> My measurements of a Shimano 105 BR5500 caliper give 64mm:34mm
> or about 1.9:1 for the C arm, and 37mm:42mm or 0.9:1 for the Y arm. The
> average of these is 1.4:1. With a 4:1 lever gives an overall ratio of
> 5.6:1.
>
> -Luns
just like avid's disk brake caliper is only activated from one side, the
effective ratio for a dual pivot caliper is that of the highest ratio
side - the rim "floats". it's therefore 2:1 [or with your measurements,
1.9:1].
|
| | | | | |
Date: 11 Nov 2007 08:25:06
From: Luns Tee
Subject: Re: rear rim seems to rub
|
In article <542dnTeaROZ_MavanZ2dnUVZ_tijnZ2d@speakeasy.net >,
jim beam <spamvortex@bad.example.net > wrote:
>just like avid's disk brake caliper is only activated from one side, the
>effective ratio for a dual pivot caliper is that of the highest ratio
>side - the rim "floats". it's therefore 2:1 [or with your measurements,
>1.9:1].
You are not accounting for the relationship between the two
pivots, and more importantly, the coupling between the arms.
Please explain the balance of forces on the Y arm with say, a
100N cable tension. If the ratio is 2:1 as you say, there would be a 200N
force at the brake pad. With its ~1:1 cable to pad ratio, how does the
Y arm support 200N at the brake pad with 100N at the cable?
-Luns
|
| | | | | | |
Date: 11 Nov 2007 00:29:33
From: jim beam
Subject: Re: rear rim seems to rub
|
Luns Tee wrote:
> In article <542dnTeaROZ_MavanZ2dnUVZ_tijnZ2d@speakeasy.net>,
> jim beam <spamvortex@bad.example.net> wrote:
>> just like avid's disk brake caliper is only activated from one side, the
>> effective ratio for a dual pivot caliper is that of the highest ratio
>> side - the rim "floats". it's therefore 2:1 [or with your measurements,
>> 1.9:1].
>
> You are not accounting for the relationship between the two
> pivots, and more importantly, the coupling between the arms.
if the rim floats, and it does, then it doesn't make any difference!
>
> Please explain the balance of forces on the Y arm with say, a
> 100N cable tension. If the ratio is 2:1 as you say, there would be a 200N
> force at the brake pad. With its ~1:1 cable to pad ratio, how does the
> Y arm support 200N at the brake pad with 100N at the cable?
see above.
|
| | | | | | | |
Date: 11 Nov 2007 08:34:37
From: Luns Tee
Subject: Re: rear rim seems to rub
|
In article <jZqdnTLIgovwIKvanZ2dnUVZ_qzinZ2d@speakeasy.net >,
jim beam <spamvortex@bad.example.net > wrote:
>Luns Tee wrote:
>> In article <542dnTeaROZ_MavanZ2dnUVZ_tijnZ2d@speakeasy.net>,
>> jim beam <spamvortex@bad.example.net> wrote:
>>> just like avid's disk brake caliper is only activated from one side, the
>>> effective ratio for a dual pivot caliper is that of the highest ratio
>>> side - the rim "floats". it's therefore 2:1 [or with your measurements,
>>> 1.9:1].
>>
>> You are not accounting for the relationship between the two
>> pivots, and more importantly, the coupling between the arms.
>
>if the rim floats, and it does, then it doesn't make any difference!
The only thing that rim float provides is that the force from
one brake pad will equal the force on the other brake pad, the rim being
unable to resist any imbalance between the two. This does not free you
from having to consider the interaction between the arms.
>> Please explain the balance of forces on the Y arm with say, a
>> 100N cable tension. If the ratio is 2:1 as you say, there would be a 200N
>> force at the brake pad. With its ~1:1 cable to pad ratio, how does the
>> Y arm support 200N at the brake pad with 100N at the cable?
>
>see above.
Your argument of float does not answer my question: how does an
arm with a 1:1 ratio from cable to pad, support a 200N pad force with
100N cable tension.
-Luns
|
| | | | | | | | |
Date: 11 Nov 2007 00:43:50
From: jim beam
Subject: Re: rear rim seems to rub
|
Luns Tee wrote:
> In article <jZqdnTLIgovwIKvanZ2dnUVZ_qzinZ2d@speakeasy.net>,
> jim beam <spamvortex@bad.example.net> wrote:
>> Luns Tee wrote:
>>> In article <542dnTeaROZ_MavanZ2dnUVZ_tijnZ2d@speakeasy.net>,
>>> jim beam <spamvortex@bad.example.net> wrote:
>>>> just like avid's disk brake caliper is only activated from one side, the
>>>> effective ratio for a dual pivot caliper is that of the highest ratio
>>>> side - the rim "floats". it's therefore 2:1 [or with your measurements,
>>>> 1.9:1].
>>> You are not accounting for the relationship between the two
>>> pivots, and more importantly, the coupling between the arms.
>> if the rim floats, and it does, then it doesn't make any difference!
>
> The only thing that rim float provides is that the force from
> one brake pad will equal the force on the other brake pad, the rim being
> unable to resist any imbalance between the two.
that's what i've been saying.
> This does not free you
> from having to consider the interaction between the arms.
but the "interaction" is simply that of centering. if you look at the
mechanism, it's not designed for any load other than the caliper's own
return spring. brake load is that of squeezing the the rim between the
"y" and "c" arms, and that can occur entirely without the centering action.
>
>
>>> Please explain the balance of forces on the Y arm with say, a
>>> 100N cable tension. If the ratio is 2:1 as you say, there would be a 200N
>>> force at the brake pad. With its ~1:1 cable to pad ratio, how does the
>>> Y arm support 200N at the brake pad with 100N at the cable?
>> see above.
>
> Your argument of float does not answer my question: how does an
> arm with a 1:1 ratio from cable to pad, support a 200N pad force with
> 100N cable tension.
because one arm has a 2:1 ratio and the rim floats.
|
| | | | | | | | | |
Date: 11 Nov 2007 09:07:16
From: Luns Tee
Subject: Re: rear rim seems to rub
|
In article <K_mdndLUKLJbXavanZ2dnUVZ_uevnZ2d@speakeasy.net >,
jim beam <spamvortex@bad.example.net > wrote:
>> This does not free you
>> from having to consider the interaction between the arms.
>
>but the "interaction" is simply that of centering. if you look at the
>mechanism, it's not designed for any load other than the caliper's own
>return spring. brake load is that of squeezing the the rim between the
>"y" and "c" arms, and that can occur entirely without the centering action.
How does the centering happen if not by transmitting a force
where the Y and C arms meet? Your neglecting this force is the heart
of why your conclusions are wrong.
>> Your argument of float does not answer my question: how does an
>> arm with a 1:1 ratio from cable to pad, support a 200N pad force with
>> 100N cable tension.
>
>because one arm has a 2:1 ratio and the rim floats.
That is not an answer. I'm not asking about the 2:1 arm, or the
rim, I'm asking about a 1:1 lever which you claim can have 100N on one
end, and 200N on the other.
-Luns
|
| |
Date: 09 Nov 2007 15:22:32
From: Joe Bernard
Subject: Re: rear rim seems to rub
|
On Nov 9, 11:26 am, jobst.bra...@stanfordalumni.org wrote:
> Tim McNamara writes:
> >> My rear rim seems to rub on a brake pad when I am standing on the
> >> pedals on steep climbs. At least that's what I THINK it is. Off
> >> the bike, everything appears trued up well with good clearance.
> >> It's my 1998 Raleigh R500 7005 alu frame with oversized tubes. Any
> >> theories? Any suggestions?
> > This is normal (it's due to lateral frame and wheel flex) and became
> > a problem with the advent of dual pivot brakes and low-ratio levers,
> > which requires the pads to be set much closer to the rim to avoid
> > the brake lever hitting the bar. Just do what the pros do- flip
> > your rear brake QR open at the bottom of the hill.
>
> Riders asked for it and got it. Old brake calipers, side/center/canti
> were all 1:1 ratio and the hand lever 4:1 mechanical advantage
> (measured from the lever crook to pivot and pivot to cable). That ws
> not enough for the riders who couldn't stop as easily as they wanted
> so the mechanical advantage was increased to a total of about 5.6:1.
>
> This required reducing pad clearance or the whole hand lever travel
> wold be used up getting the pads to touch the rim. To do that, a
> precisely centered caliper was needed and the brute force method was
> to use two pivot points, one on axis and the other off to one side.
> This causes the pad on the short arm to climb into the tire with wear.
>
> Accurate centering could have been achieved by coiling the return
> spring around the center bolt instead of having a spring with
> "elephant ears" on either side of center. The centers of rotation of
> the return spring is the center of the elephant ears and that causes
> cosine error, the sliding motion you can readily see on a dual pivot
> caliper. They even have a sliding plastic sleeve to accommodate that
> unnecessary motion.
>
> Campagnolo was aware that riders climbed hills with open QR's on the
> rear brake and offered a 1:1 single pivot brake with good pad
> clearance for the rear, where heavy braking is not done anyway.
>
> Today, closely spaced rear hub flanges work together with low pad
> clearance to make brakes drag when climbing. This is more noticeable
> when riding in rain, when wet road grit makes an audible complaint.
>
> Jobst Brandt
Does your wheel wiggle back and forth when you tug on it? Your hub-
bearing adjustment may need attention. Hard torque will pull the wheel
to the drivetrain side, rubbing your brakes.
|
| |
Date: 09 Nov 2007 12:08:51
From: Tim McNamara
Subject: Re: rear rim seems to rub
|
Jim Flom wrote:
> My rear rim seems to rub on a brake pad when I am standing on the pedals on
> steep climbs. At least that's what I THINK it is. Off the bike, everything
> appears trued up well with good clearance. It's my 1998 Raleigh R500 7005
> alu frame with oversized tubes.
>
> Any theories? Any suggestions?
This is normal (it's due to lateral frame and wheel flex) and became a
problem with the advent of dual pivot brakes and low-ratio levers, which
requires the pads to be set much closer to the rim to avoid the brake
lever hitting the bar. Just do what the pros do- flip your rear brake
QR open at the bottom of the hill.
|
| | |
Date: 09 Nov 2007 19:26:25
From:
Subject: Re: rear rim seems to rub
|
Tim McNamara writes:
>> My rear rim seems to rub on a brake pad when I am standing on the
>> pedals on steep climbs. At least that's what I THINK it is. Off
>> the bike, everything appears trued up well with good clearance.
>> It's my 1998 Raleigh R500 7005 alu frame with oversized tubes. Any
>> theories? Any suggestions?
> This is normal (it's due to lateral frame and wheel flex) and became
> a problem with the advent of dual pivot brakes and low-ratio levers,
> which requires the pads to be set much closer to the rim to avoid
> the brake lever hitting the bar. Just do what the pros do- flip
> your rear brake QR open at the bottom of the hill.
Riders asked for it and got it. Old brake calipers, side/center/canti
were all 1:1 ratio and the hand lever 4:1 mechanical advantage
(measured from the lever crook to pivot and pivot to cable). That ws
not enough for the riders who couldn't stop as easily as they wanted
so the mechanical advantage was increased to a total of about 5.6:1.
This required reducing pad clearance or the whole hand lever travel
wold be used up getting the pads to touch the rim. To do that, a
precisely centered caliper was needed and the brute force method was
to use two pivot points, one on axis and the other off to one side.
This causes the pad on the short arm to climb into the tire with wear.
Accurate centering could have been achieved by coiling the return
spring around the center bolt instead of having a spring with
"elephant ears" on either side of center. The centers of rotation of
the return spring is the center of the elephant ears and that causes
cosine error, the sliding motion you can readily see on a dual pivot
caliper. They even have a sliding plastic sleeve to accommodate that
unnecessary motion.
Campagnolo was aware that riders climbed hills with open QR's on the
rear brake and offered a 1:1 single pivot brake with good pad
clearance for the rear, where heavy braking is not done anyway.
Today, closely spaced rear hub flanges work together with low pad
clearance to make brakes drag when climbing. This is more noticeable
when riding in rain, when wet road grit makes an audible complaint.
Jobst Brandt
|
| | | |
Date: 10 Nov 2007 06:19:59
From: jim beam
Subject: Re: rear rim seems to rub
|
jobst.brandt@stanfordalumni.org wrote:
> Tim McNamara writes:
>
>>> My rear rim seems to rub on a brake pad when I am standing on the
>>> pedals on steep climbs. At least that's what I THINK it is. Off
>>> the bike, everything appears trued up well with good clearance.
>>> It's my 1998 Raleigh R500 7005 alu frame with oversized tubes. Any
>>> theories? Any suggestions?
>
>> This is normal (it's due to lateral frame and wheel flex) and became
>> a problem with the advent of dual pivot brakes and low-ratio levers,
>> which requires the pads to be set much closer to the rim to avoid
>> the brake lever hitting the bar. Just do what the pros do- flip
>> your rear brake QR open at the bottom of the hill.
>
> Riders asked for it and got it. Old brake calipers, side/center/canti
> were all 1:1 ratio and the hand lever 4:1 mechanical advantage
> (measured from the lever crook to pivot and pivot to cable). That ws
> not enough for the riders who couldn't stop as easily as they wanted
> so the mechanical advantage was increased to a total of about 5.6:1.
actually, the total is more like 8:1 - the ratio of arm lengths on the
"C" arm of a dual pivot caliper is ~2:1. [62mm:31mm for dura-ace 7700.]
the mechanical ratio is not affected by the 1:1 ratio on the "Y" arm
side of the caliper because the lateral stiffness of the rim is many
orders of magnitude less than that of the caliper so the rim simply
"floats".
>
> This required reducing pad clearance or the whole hand lever travel
> wold be used up getting the pads to touch the rim. To do that, a
> precisely centered caliper was needed and the brute force method was
> to use two pivot points, one on axis and the other off to one side.
> This causes the pad on the short arm to climb into the tire with wear.
>
> Accurate centering could have been achieved by coiling the return
> spring around the center bolt instead of having a spring with
> "elephant ears" on either side of center. The centers of rotation of
> the return spring is the center of the elephant ears and that causes
> cosine error, the sliding motion you can readily see on a dual pivot
> caliper. They even have a sliding plastic sleeve to accommodate that
> unnecessary motion.
>
> Campagnolo was aware that riders climbed hills with open QR's on the
> rear brake and offered a 1:1 single pivot brake with good pad
> clearance for the rear, where heavy braking is not done anyway.
>
> Today, closely spaced rear hub flanges work together with low pad
> clearance to make brakes drag when climbing. This is more noticeable
> when riding in rain, when wet road grit makes an audible complaint.
>
> Jobst Brandt
|
| | | | |
Date: 10 Nov 2007 16:00:46
From:
Subject: Re: rear rim seems to rub
|
To assess the mechanical advantage of a dual pivot caliper, measure
the cable stroke and pad closure. The caliper has the same effect of
the centerpull with two arms, each twice as long as the pivot-to-pad
dimension, but there are two of them, each providing half the motion.
It was this geometric gimmick that led people to believe that hey were
twice as powerful grabbers as sidepull brakes of that time. It wasn't
so.
Jobst Brandt
|
| | | | | |
Date: 10 Nov 2007 10:32:47
From: jim beam
Subject: Re: rear rim seems to rub
|
jobst.brandt@stanfordalumni.org wrote:
> To assess the mechanical advantage of a dual pivot caliper, measure
> the cable stroke and pad closure.
that's inaccurate and pointless. the lever ratios are easy and much
more accessible. maybe that's why you got it wrong?
> The caliper has the same effect of
> the centerpull with two arms, each twice as long as the pivot-to-pad
> dimension, but there are two of them, each providing half the motion.
doesn't matter - the rim effectively floats. one pad could be static
for all it matters to mechanical advantage. indeed, avid mechanical
disk brakes use this principle.
> It was this geometric gimmick that led people to believe that hey were
> twice as powerful grabbers as sidepull brakes of that time. It wasn't
> so.
maybe to people that didn't measure their lever ratios correctly.
|
| | | |
Date: 10 Nov 2007 06:37:48
From: Jim Flom
Subject: Re: rear rim seems to rub
|
<jobst.brandt@stanfordalumni.org > wrote in message
news:4734b461$0$14150$742ec2ed@news.sonic.net...
> Tim McNamara writes:
>
>>> My rear rim seems to rub on a brake pad when I am standing on the
>>> pedals on steep climbs. At least that's what I THINK it is. Off
>>> the bike, everything appears trued up well with good clearance.
>>> It's my 1998 Raleigh R500 7005 alu frame with oversized tubes. Any
>>> theories? Any suggestions?
>
>> This is normal (it's due to lateral frame and wheel flex) and became
>> a problem with the advent of dual pivot brakes and low-ratio levers,
>> which requires the pads to be set much closer to the rim to avoid
>> the brake lever hitting the bar. Just do what the pros do- flip
>> your rear brake QR open at the bottom of the hill.
>
> Riders asked for it and got it. Old brake calipers, side/center/canti
> were all 1:1 ratio and the hand lever 4:1 mechanical advantage
> (measured from the lever crook to pivot and pivot to cable). That ws
> not enough for the riders who couldn't stop as easily as they wanted
> so the mechanical advantage was increased to a total of about 5.6:1.
>
> This required reducing pad clearance or the whole hand lever travel
> wold be used up getting the pads to touch the rim. To do that, a
> precisely centered caliper was needed and the brute force method was
> to use two pivot points, one on axis and the other off to one side.
> This causes the pad on the short arm to climb into the tire with wear.
>
> Accurate centering could have been achieved by coiling the return
> spring around the center bolt instead of having a spring with
> "elephant ears" on either side of center. The centers of rotation of
> the return spring is the center of the elephant ears and that causes
> cosine error, the sliding motion you can readily see on a dual pivot
> caliper. They even have a sliding plastic sleeve to accommodate that
> unnecessary motion.
>
> Campagnolo was aware that riders climbed hills with open QR's on the
> rear brake and offered a 1:1 single pivot brake with good pad
> clearance for the rear, where heavy braking is not done anyway.
>
> Today, closely spaced rear hub flanges work together with low pad
> clearance to make brakes drag when climbing. This is more noticeable
> when riding in rain, when wet road grit makes an audible complaint.
And it is precisely in the fall BC rain that I'm noticing it. Never noticed
it before this (or last?) year, but I'm riding in the rain a lot more right
now.
Someone asked about the rim. It's a Mavic something P-10 (it looks like),
but the label is pretty worn so I am not sure.
I have never liked this hub. I think it's a low end Shimano, possibly an RX
100. It was impossible to repack the hub without some wobble, until this
fall. I managed to eliminate any lateral looseness in the hub, and it spun
well, and quietly. But I've been riding in so much crud, so much rain and
road grit that the hub has become audible when I spin it. I gave it to my
LBS last year to repack and they did such a crappy job (they're otherwise
good -- few complaints -- I support them) that I repacked it myself two
weeks later. I _never_ have this kind of problem with my Campy components
on my other bike.
Brakes are Ultegra. I guess I'll open up the quick release. I'll just have
to man up on that one steep descent.
I'm tempted to get a new hub and get a well-built wheel. Sounds like it
won't eliminate the rubbing when I climb but at least it may be easier to
maintain.
Thanks fellas,
Jim
--
JF
"A really great man is known by three signs,--generosity in the design,
humanity in the execution, and moderation in success."
- Karl Otto von Schonhausen Bismarck
|
| | | |
Date: 09 Nov 2007 19:48:55
From: jim beam
Subject: Re: rear rim seems to rub
|
jobst.brandt@stanfordalumni.org wrote:
> Tim McNamara writes:
>
>>> My rear rim seems to rub on a brake pad when I am standing on the
>>> pedals on steep climbs. At least that's what I THINK it is. Off
>>> the bike, everything appears trued up well with good clearance.
>>> It's my 1998 Raleigh R500 7005 alu frame with oversized tubes. Any
>>> theories? Any suggestions?
>
>> This is normal (it's due to lateral frame and wheel flex) and became
>> a problem with the advent of dual pivot brakes and low-ratio levers,
>> which requires the pads to be set much closer to the rim to avoid
>> the brake lever hitting the bar. Just do what the pros do- flip
>> your rear brake QR open at the bottom of the hill.
>
> Riders asked for it and got it. Old brake calipers, side/center/canti
> were all 1:1 ratio and the hand lever 4:1 mechanical advantage
> (measured from the lever crook to pivot and pivot to cable). That ws
> not enough for the riders who couldn't stop as easily as they wanted
> so the mechanical advantage was increased to a total of about 5.6:1.
so? dual pivot offer greater braking leverage and toe control. why do
you have a problem with that?
>
> This required reducing pad clearance or the whole hand lever travel
> wold be used up getting the pads to touch the rim.
so?
> To do that, a
> precisely centered caliper was needed and the brute force method was
> to use two pivot points, one on axis and the other off to one side.
> This causes the pad on the short arm to climb into the tire with wear.
so, maintain your bike more frequently!!
>
> Accurate centering could have been achieved by coiling the return
> spring around the center bolt instead of having a spring with
> "elephant ears" on either side of center. The centers of rotation of
> the return spring is the center of the elephant ears and that causes
> cosine error, the sliding motion you can readily see on a dual pivot
> caliper. They even have a sliding plastic sleeve to accommodate that
> unnecessary motion.
1. shimano single pivots have exactly the same plastic sleeved sliders.
2. the motion is not "unnecessary", it's a function of the leverage!
>
> Campagnolo was aware that riders climbed hills with open QR's on the
> rear brake and offered a 1:1 single pivot brake with good pad
> clearance for the rear, where heavy braking is not done anyway.
they "offer" it on chorus and record for weight savings, not for any
mysterious geometrical reasoning. the lower end models remain as dual
pivot. try checking facts for a change by reading campy's own literature.
>
> Today, closely spaced rear hub flanges work together with low pad
> clearance to make brakes drag when climbing. This is more noticeable
> when riding in rain, when wet road grit makes an audible complaint.
this is exactly the same as old bikes with single pivot if pads are run
that close to the rim. don't demonize what you yourself don't have
experience of.
|
| |
Date: 09 Nov 2007 09:20:51
From: russellseaton1@yahoo.com
Subject: Re: rear rim seems to rub
|
On Nov 9, 10:37 am, "Jim Flom" <jim.flomREM...@telus.net > wrote:
> My rear rim seems to rub on a brake pad when I am standing on the pedals on
> steep climbs. At least that's what I THINK it is. Off the bike, everything
> appears trued up well with good clearance. It's my 1998 Raleigh R500 7005
> alu frame with oversized tubes.
>
> Any theories? Any suggestions?
>
> --
> JF
>
> "A really great man is known by three signs,--generosity in the design,
> humanity in the execution, and moderation in success."
> - Karl Otto von Schonhausen Bismarck
What specific rim/wheel are you using on the rear of the bike? Highly
doubt the frame/bike matters. Any flexibility or lack thereof in the
frame/bottom bracket area will not get transferred to the seatstay
bridge where the brake caliper is mounted. If it did then you have
far more important/immediate issues to deal with.
It is somewhat common to see pro bicyclists with open brake quick
releases (calipers with Shimano and Ergo levers with Campagnolo) when
climbing mountains. Scan through pictures on the Cycling News website
and you will find them.
This is a link to tests Damon Rinard did measuring lateral flexibility
on wheels.
http://www.sheldonbrown.com/rinard/
http://www.sheldonbrown.com/rinard/wheel/index.htm
|
| | |
Date: 09 Nov 2007 19:44:53
From: jim beam
Subject: Re: rear rim seems to rub
|
russellseaton1@yahoo.com wrote:
> On Nov 9, 10:37 am, "Jim Flom" <jim.flomREM...@telus.net> wrote:
>> My rear rim seems to rub on a brake pad when I am standing on the pedals on
>> steep climbs. At least that's what I THINK it is. Off the bike, everything
>> appears trued up well with good clearance. It's my 1998 Raleigh R500 7005
>> alu frame with oversized tubes.
>>
>> Any theories? Any suggestions?
>>
>> --
>> JF
>>
>> "A really great man is known by three signs,--generosity in the design,
>> humanity in the execution, and moderation in success."
>> - Karl Otto von Schonhausen Bismarck
>
> What specific rim/wheel are you using on the rear of the bike? Highly
> doubt the frame/bike matters. Any flexibility or lack thereof in the
> frame/bottom bracket area will not get transferred to the seatstay
> bridge where the brake caliper is mounted. If it did then you have
> far more important/immediate issues to deal with.
>
> It is somewhat common to see pro bicyclists with open brake quick
> releases (calipers with Shimano and Ergo levers with Campagnolo) when
> climbing mountains. Scan through pictures on the Cycling News website
> and you will find them.
indeed. not a hard practice to copy!
>
> This is a link to tests Damon Rinard did measuring lateral flexibility
> on wheels.
>
> http://www.sheldonbrown.com/rinard/
> http://www.sheldonbrown.com/rinard/wheel/index.htm
>
|
|
