Candid comments from Cotic on disks and QRs

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Date: 07 Nov 2007 03:30:13
From: james.annan@gmail.com
Subject: Candid comments from Cotic on disks and QRs

I know their roadhog forks (with the disk mount on the front of the RH
fork leg) have been commented on before, but their explanation for
this design is refreshingly candid:

"Axle movement under disc braking is now a fairly well known
phenomenon in mountain biking. Basically with the caliper positioned
left rear (usual place), and a vertical dropout, there is a reaction
of the braking force which tends to push the axle out of the dropout,
hence you're relying on the friction of your QR to counteract this
rather than a completely mechanical stop. Most manufacturers have
moved to a slightly forward facing dropout to counteract this.

"We've actually never experienced any trouble with this on our
mountain bikes, but during prototype testing of the ROADHOG fork -
which had the disc mount in the usual left rear position - we did
actually experience some axle movement. Nothing actually came undone,
but after some serious downhill braking on fast roads, the rotors
would be rubbing a touch and the wheel would 'clunk' home in the
dropout when we undid the axle nuts. This was clearly unacceptable, so
we set about finding a solution."

<http://www.cotic.co.uk/geek/ >

I suppose the usual suspects will claim that this just proves that
Cotic do not know how to use QRs...

James

Date: 13 Nov 2007 23:59:22
From: Ed Pirrero
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 13, 3:43 pm, jobst.bra...@stanfordalumni.org wrote:
> Ed Pirrero writes:
> >> The resistance to the idea that disk brake forces could loosen a
> >> quick release appears to be faith based.
> > Who argues that it can't happen?
>
> ...and that the reaction force of the brake acts downward on one end
> of the axle, equivalent to ((wheel diameter / disk diameter) x rider
> weight) in magnitude. When the axle disengages from the dropout on
> one end, wheel canting WILL lock it solidly against rotation.
>
> The non "faith based" have not denied this, although they avoid
> confronting that force and where and how it acts.

AFAICT, the only people avoiding facts are those who claim that the
hypothesis is actually reflected in the real world data. Unless there
is a whole body of controlled experimentation that has not been
quoted, the small handful of examples of QR loosening cannot be
separated from the background noise of user error. And if facts are
the basis of the discussion, rather than faith, it should be admitted
that not one of those examples could be used as data, if it came down
to dicussing the available information in a scientific manner.

E.P.

Date: 13 Nov 2007 23:33:44
From: Ed Pirrero
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 12, 6:27 pm, Tom Sherman <sunsetss0...@REMOVETHISyahoo.com >
wrote:

> The resistance to the idea that disc brake forces could loosen a quick
> release appears to be faith based.

Who argues that it can't happen?

E.P.

Date: 13 Nov 2007 23:43:58
From:
Subject: Re: Candid comments from Cotic on disks and QRs

Ed Pirrero writes:

>> The resistance to the idea that disk brake forces could loosen a
>> quick release appears to be faith based.

> Who argues that it can't happen?

...and that the reaction force of the brake acts downward on one end
of the axle, equivalent to ((wheel diameter / disk diameter) x rider
weight) in magnitude. When the axle disengages from the dropout on
one end, wheel canting WILL lock it solidly against rotation.

The non "faith based" have not denied this, although they avoid
confronting that force and where and how it acts.

Jobst Brandt

Date: 14 Nov 2007 06:34:37
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <473a36be$0$14127$742ec2ed@news.sonic.net >,
jobst.brandt@stanfordalumni.org says...
>
> ...and that the reaction force of the brake acts downward on one end
> of the axle, equivalent to ((wheel diameter / disk diameter) x rider
> weight) in magnitude. When the axle disengages from the dropout on
> one end, wheel canting WILL lock it solidly against rotation.
>

But by what mechanism do you propose that the QR gets over the lawyers
lips? Are you proposing that the lawyers lips are sheared off by the QR
nut or that the skewer itself stretched to get over them?

If it is the QR continues to loosen until it is loose enough to eject
why is it that nobody notices the wheel canting over and rubbing against
the disk pads after the initial loosening but before its loosened enough
to get over the lawyers lips ? Bikers are very sensitive to their disk
brakes rubbing IME.

And what is the loosening force that continues to drive the loosening
once the QR has just loosened enough to just lose pressure contact with
the drop out and before its loose enough to get over the lawyers lips?
Please refer to the mechanism that disables the nylock insert in the QR
nut to enable loosening during this phase.

Lots of still unanswered questions as to how a wheel gets to the stage
you suggest even if it the QR does loosen.

--
Tony

"The single biggest problem in communication is the illusion that it has
taken place"
George Bernard Shaw

Date: 14 Nov 2007 19:44:39
From: Steve Gravrock
Subject: Re: Candid comments from Cotic on disks and QRs

On 2007-11-14, Tony Raven <junk@raven-family.invalid > wrote:

> If it is the QR continues to loosen until it is loose enough to eject
> why is it that nobody notices the wheel canting over and rubbing against
> the disk pads after the initial loosening but before its loosened enough
> to get over the lawyers lips ? Bikers are very sensitive to their disk
> brakes rubbing IME.

Mountain bikers using disc brakes on long descents are less so. Rotors
tend to warp under heavy sustained braking, and the effects of loosening
could be lost in that noise.

Date: 14 Nov 2007 08:55:48
From: Mark McNeill
Subject: Re: Candid comments from Cotic on disks and QRs

Response to Tony Raven
> Please refer to the mechanism that disables the nylock insert in the QR
> nut to enable loosening during this phase.

I remember being curious about this point last time the subject came up,
and my curiosity wasn't satisfied; which made me more curious ;-).

Nylocks tend to become considerably weaker with use: we have several
hundred 12mm nylocks in regular use at work, and find that after a
comparatively small number of cycles, the torque required to take them
off a bolt will fall from 6-inch-spanner-stylee to being easily turned
with the fingers: when they reach this state, turning of the instrument
they're fitted to will routinely unscrew them sufficiently to disengage
the spring washer they're supposed to keep in compression. [Needless to
say - and in keeping with most threads on this subject ;-) - this is
informal observation: no hard numbers.]

It's tempting to infer that the much smaller and lower-torque nylocks
used in skewers are subject to a similar type of degradation in
performance. Does anybody know? And where nylocks undergo
tightening/loosening cycles in critical applications in industry, do
they come with recommendations for their regular replacement?

--
Mark, UK
"A wartime Minister of Information is compelled, in the national
interest, to such continuous acts of duplicity that even his natural
hair must grow to resemble a wig."

Date: 14 Nov 2007 11:19:28
From: A Muzi
Subject: Re: Candid comments from Cotic on disks and QRs

> Response to Tony Raven
>> Please refer to the mechanism that disables the nylock insert in the QR
>> nut to enable loosening during this phase.

Mark McNeill wrote:
> I remember being curious about this point last time the subject came up,
> and my curiosity wasn't satisfied; which made me more curious ;-).
>
> Nylocks tend to become considerably weaker with use: we have several
> hundred 12mm nylocks in regular use at work, and find that after a
> comparatively small number of cycles, the torque required to take them
> off a bolt will fall from 6-inch-spanner-stylee to being easily turned
> with the fingers: when they reach this state, turning of the instrument
> they're fitted to will routinely unscrew them sufficiently to disengage
> the spring washer they're supposed to keep in compression. [Needless to
> say - and in keeping with most threads on this subject ;-) - this is
> informal observation: no hard numbers.]
>
> It's tempting to infer that the much smaller and lower-torque nylocks
> used in skewers are subject to a similar type of degradation in
> performance. Does anybody know? And where nylocks undergo
> tightening/loosening cycles in critical applications in industry, do
> they come with recommendations for their regular replacement?

Real skewer nuts have brass inserts which press on the thread with a
spring loop.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Date: 14 Nov 2007 16:40:00
From: Jasper Janssen
Subject: Re: Candid comments from Cotic on disks and QRs

On Wed, 14 Nov 2007 08:55:48 -0000, Mark McNeill
<markonnewsgroups@yahoo.co.uk > wrote:

>It's tempting to infer that the much smaller and lower-torque nylocks
>used in skewers are subject to a similar type of degradation in
>performance. Does anybody know? And where nylocks undergo
>tightening/loosening cycles in critical applications in industry, do
>they come with recommendations for their regular replacement?

In aircraft, I believe Nylocks cannot be reused at all.

There are nylocks in skewers? I'd never noticed..

Jasper

Date: 14 Nov 2007 12:28:01
From: _
Subject: Re: Candid comments from Cotic on disks and QRs

On Wed, 14 Nov 2007 08:55:48 -0000, Mark McNeill wrote:

> Nylocks tend to become considerably weaker with use: we have several
> hundred 12mm nylocks in regular use at work, and find that after a
> comparatively small number of cycles, the torque required to take them
> off a bolt will fall from 6-inch-spanner-stylee to being easily turned
> with the fingers: when they reach this state, turning of the instrument
> they're fitted to will routinely unscrew them sufficiently to disengage
> the spring washer they're supposed to keep in compression. [Needless to
> say - and in keeping with most threads on this subject ;-) - this is
> informal observation: no hard numbers.]
>
> It's tempting to infer that the much smaller and lower-torque nylocks
> used in skewers are subject to a similar type of degradation in
> performance. Does anybody know? And where nylocks undergo
> tightening/loosening cycles in critical applications in industry, do
> they come with recommendations for their regular replacement?

Nylocs are single use, in situations where the locking action is mandatory.

And in such situations, there are better solutions.

Date: 14 Nov 2007 11:00:12
From: Rob Morley
Subject: Re: Candid comments from Cotic on disks and QRs

In article <MPG.21a4c871fa2b55a4989a41@news.nildram.co.uk >, Mark McNeill
markonnewsgroups@yahoo.co.uk says...

> It's tempting to infer that the much smaller and lower-torque nylocks
> used in skewers are subject to a similar type of degradation in
> performance. Does anybody know? And where nylocks undergo
> tightening/loosening cycles in critical applications in industry, do
> they come with recommendations for their regular replacement?
>
I know that in some applications (a few years ago I knew a bloke with a
hang glider) you're not allowed to reuse a nyloc - once you unscrew it
it's scrap. Presumably this is the same in many critical applications.
Maybe we should be applying threadlock compound every time we fit a
wheel. :-)

Date: 14 Nov 2007 21:03:57
From: dabac
Subject: Re: Candid comments from Cotic on disks and QRs

Mark McNeill Wrote:
> ...Nylocks tend to become considerably weaker with use....where nylock
> undergo tightening/loosening cycles in critical applications i
> industry, do they come with recommendations for their regula
> replacement?

They certainly do. Don't remember the specifics too well, but I believ
that for critical applications (like ball joints in vehicle steerin
linkages) they're considered single-use items. I'll see if I can look i
up somewhere

--
dabac

Date: 13 Nov 2007 20:17:21
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

jobst.brandt@stanfordalumni.org wrote:
> Ed Pirrero writes:
>
>>> The resistance to the idea that disk brake forces could loosen a
>>> quick release appears to be faith based.
>
>> Who argues that it can't happen?
>
> ...and that the reaction force of the brake acts downward on one end
> of the axle, equivalent to ((wheel diameter / disk diameter) x rider
> weight) in magnitude. When the axle disengages from the dropout on
> one end, wheel canting WILL lock it solidly against rotation.

so what? there is force on my fork crown that will cause catastrophe
should it actually fail. but its strength exceeds that force by
sufficient margin for the fork to be considered "reliable". same goes
for my crank arms, the stem gripping my steering tube, etc. a properly
secured q.r., with properly serrated axle faces, is no different since
the retention force generated exceeds ejection force many times.

>
> The non "faith based" have not denied this, although they avoid
> confronting that force and where and how it acts.

where have the competent engineers gone? all we seem to have these days
are fools bamboozled and deceived by deliberately slanted analysis,
where "theory" has absolutely no correlation with fact.

Date: 13 Nov 2007 16:47:24
From: Ed Pirrero
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 13, 1:06 am, Peter Clinch <p.j.cli...@dundee.ac.uk > wrote:
> Ed Pirrero wrote:
> > Except for the odd fact that the actual ejections never actually seem
> > to take place.
>
> Gravity is a pretty useful counter to them, and since braking will tend
> to force the fork into the ground it'll be harder still, but with the
> vagaries of MTB terrain meaning the ground won't always do what's
> expected of it, again I ask why not have a system that will fail safe
> rather than unsafe?

According to the math previously presented, gravity is not strong
enough to retain the wheel.

The philosophical question you pose is a red herring. If the current
design doesn't actually fail, but merely only could *hypothetically*
fail, then why expend any effort on redesign, other than as a
marketing exercise at product differentiation?

The proven failures of the design are pretty few and far between. In
fact, I think there has been a single proven incident of wheel
ejection. The one that Annan originally described.

E.P.

Date: 13 Nov 2007 05:54:28
From:
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 13, 7:30 am, Peter Clinch <p.j.cli...@dundee.ac.uk > wrote:
> Alan Braggins wrote:
> > Simon seems conviced that Cannondale Lefty style "forks" are the way of
> > the future. What do you know that he and Cannondale don't?
>
> I suspect /almost/ eveyone knows that 559 wheels as used on the Lefty
> are smaller than the 700c that it looks like the Cotic fork is designed
> for...
>
> Pete.
> --
> Peter Clinch Medical Physics IT Officer
> Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
> Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
> net p.j.cli...@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/

But I suspect/ almost/ everyone does not know that Cannondale also
makes an 80mm 29" version of the Lefty. Not that it matters. Even on
the 26" version, the axle to crown distance is longer than any road
fork.

Date: 13 Nov 2007 14:05:04
From: Peter Clinch
Subject: Re: Candid comments from Cotic on disks and QRs

unforgiven99@juno.com wrote:

> But I suspect/ almost/ everyone does not know that Cannondale also
> makes an 80mm 29" version of the Lefty. Not that it matters. Even on
> the 26" version, the axle to crown distance is longer than any road
> fork.

And the whole thing is also rather chunkier and heavier than any road
fork. Monoblades haven't caught on in road racing for very good reasons
(i.e., unlike the usual "the UCI banning them" case).

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/

Date: 13 Nov 2007 20:23:41
From: Tom Sherman
Subject: Re: Candid comments from Cotic on disks and QRs

Peter Clinch wrote:
> unforgiven99@juno.com wrote:
>
>> But I suspect/ almost/ everyone does not know that Cannondale also
>> makes an 80mm 29" version of the Lefty. Not that it matters. Even on
>> the 26" version, the axle to crown distance is longer than any road
>> fork.
>
> And the whole thing is also rather chunkier and heavier than any road
> fork. Monoblades haven't caught on in road racing for very good reasons
> (i.e., unlike the usual "the UCI banning them" case).

But monoblades eliminate chain to fork rubbing.

--
Tom Sherman - Holstein-Friesland Bovinia
"the grinning buddy bear carries a fork." - g.d.

Date: 14 Nov 2007 09:25:02
From: Dave Larrington
Subject: Re: Candid comments from Cotic on disks and QRs

In news:fhdm7a$531$2@registered.motzarella.org,
Tom Sherman <sunsetss0003@REMOVETHISyahoo.com > tweaked the Babbage-Engine to
tell us:
> Peter Clinch wrote:
>> unforgiven99@juno.com wrote:
>>
>>> But I suspect/ almost/ everyone does not know that Cannondale also
>>> makes an 80mm 29" version of the Lefty. Not that it matters. Even
>>> on the 26" version, the axle to crown distance is longer than any
>>> road fork.
>>
>> And the whole thing is also rather chunkier and heavier than any road
>> fork. Monoblades haven't caught on in road racing for very good
>> reasons (i.e., unlike the usual "the UCI banning them" case).
>
> But monoblades eliminate chain to fork rubbing.

Which is a non-issue as far as Cotic are concerned...

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk >
Trees, once grown in large numbers, make perfect forests.

Date: 13 Nov 2007 16:38:18
From: Alan Braggins
Subject: Re: Candid comments from Cotic on disks and QRs

In article <5ptpafFsug83U2@mid.individual.net >, Peter Clinch wrote:
>unforgiven99@juno.com wrote:
>
>> But I suspect/ almost/ everyone does not know that Cannondale also
>> makes an 80mm 29" version of the Lefty. Not that it matters. Even on
>> the 26" version, the axle to crown distance is longer than any road
>> fork.
>
>And the whole thing is also rather chunkier and heavier than any road
>fork. Monoblades haven't caught on in road racing for very good reasons
>(i.e., unlike the usual "the UCI banning them" case).

Nor have disc brakes, and Tom suggested "a single-sided wheel mount with
front disc brakes". And while I'm not convinced that the UCI regulations
don't play a part, "aren't ideal for road racing" is different from "tend
not to work terribly well with full sized wheels".

Date: 13 Nov 2007 10:03:11
From: bjw@mambo.ucolick.org
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 12, 7:27 pm, Ed Pirrero <gcmschem...@gmail.com > wrote:

> > People have
> > reported loose quick release nuts at the bottom of a
> > run that the know were tight at the top of the run.
>
> Mostly in Great Britain. In fact, all but one "report" of such events
> have been from Great Britain.

There you go, it's obviously caused by driving on the
left then. Must have something to do with how you
put the bike on the car rack and the Coriolis force.

IIRC, James Annan stirred up the hornet's nest, and he's
Scottish, but he lives in Japan. Where they drive
on the left!! Q.E.D.

Ben

Date: 13 Nov 2007 02:27:16
From: Ed Pirrero
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 12, 2:59 pm, Michael Press <rub...@pacbell.net > wrote:
> In article <5pqoi2Fsn4m...@mid.individual.net>,
> Peter Clinch <p.j.cli...@dundee.ac.uk> wrote:
>
> > Tony Raven wrote:
>
> > > Most marketing claims have some tenuous link with reality but they admit
> > > that its not a problem they have ever seen on the mountain bikes.
>
> > It's not a problem if you do up your QRs properly, and gravity tends to
> > work against wheel ejection too. OTOH, why not have a system that fails
> > safe, rather than unsafe, if you /don't/ do up your QRs properly?
>
> The reaction force can loosen even a properly tightened
> quick release nut.

Allegedly.

> The addition of
> intermittent forces outward can "walk out" the quick
> release nut.

Allegedly.

> This is not theoretical.

Except for the odd fact that the actual ejections never actually seem
to take place.

> People have
> reported loose quick release nuts at the bottom of a
> run that the know were tight at the top of the run.

Mostly in Great Britain. In fact, all but one "report" of such events
have been from Great Britain.

No matter how well-founded the hypothesis happens to be, if the
predicted action never actually happens, then there is room to modify
the hypothesis.

E.P.

Date: 13 Nov 2007 09:06:23
From: Peter Clinch
Subject: Re: Candid comments from Cotic on disks and QRs

Ed Pirrero wrote:

> Except for the odd fact that the actual ejections never actually seem
> to take place.

Gravity is a pretty useful counter to them, and since braking will tend
to force the fork into the ground it'll be harder still, but with the
vagaries of MTB terrain meaning the ground won't always do what's
expected of it, again I ask why not have a system that will fail safe
rather than unsafe?

Pete.--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/

Date: 12 Nov 2007 16:47:38
From:
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 12, 10:24 am, Tony Raven <j...@raven-family.invalid > wrote:
>
> I think you have missed out that you can get insight into the mind by
> looking at patterns of behaviour such as whether they tackled the
> problem elsewhere in their range. The fact they haven't tends to
> indicate they don't really see it as much of a problem. People are
> willing enough to offer detailed insights here into the minds of
> motorists based on patterns of behaviour ;-)
>
> Yes, there may be multiple reasons with hindsight but usually there is a
> single triggering event that leads you to change a design away from the
> established standard. You then hang other rationalisations around it to
> strengthen the case.
>
> Whatever it is though they clearly don't see it as significant enough to
> bother with on their other bikes.

You seem to be ignoring certain facts. One is that this small company
has limited influence on the designs of major fork manufacturers. The
second is that, in this universe, events occur only as time passes,
not instantaneously!

If Cotic were able to get special versions of suspension forks made to
their spec - which is doubtful - it would certainly take them a while
to negotiate such changes with their fork suppliers. It would take
much less time for them to modify the design of the one fork they've
designed and built themselves.

I think action on this issue will progress fairly slowly, unless there
is a large and successful lawsuit. There's a lot of investment in
place for the current design, and problems, although real, are not
very common.

- Frank Krygowski

Date: 12 Nov 2007 04:31:38
From:
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 12, 6:48 am, Tony Raven <j...@raven-family.invalid > wrote:
> In article <5pqoi2Fsn4m...@mid.individual.net>, p.j.cli...@dundee.ac.uk
> says...
>
> > Tony Raven wrote:
>
> > > Most marketing claims have some tenuous link with reality but they admit
> > > that its not a problem they have ever seen on the mountain bikes.
>
> > It's not a problem if you do up your QRs properly, and gravity tends to
> > work against wheel ejection too. OTOH, why not have a system that fails
> > safe, rather than unsafe, if you /don't/ do up your QRs properly?
>
> That's a different discussion. The question being debated is whether
> that was the fundamental reason they did it (but didn't bother on any of
> their other bikes) or whether it was a bit of added marketing fluff
> having already decided they needed to do it to fit the mudguard stays to
> the fork. What was the cause and what was incidental?
>
> --
> Tony
>
> "The single biggest problem in communication is the illusion that it has
> taken place"
> George Bernard Shaw

Planet Bike already figured out the fender problem. They simply
supply an extra long mounting bolt with a spacer tube so that the
stays clear the brake caliper. This is a much smarter and more
elegant solution than moving the brake.

Mounting tab fatigue is pretty much a non-issue. There are already
plenty of welds on a bike that are in tension, and if designed
appropriately this can be reliable. The part that worries me, which
is the one that Cotic has no control over, is the caliper itself.
Some caliper bodies might handle the backwards loading better than
others, but none of them were designed for it. If there's going to be
a catastrophic fatigue failure it's going to happen in the caliper,
not the mounting tab.

Date: 11 Nov 2007 04:32:09
From:
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 10, 1:32 pm, jim beam <spamvor...@bad.example.net > wrote, about
front mounted brake calipers:

>
> can you guarantee the weld quality? because that is the point of issue.
> poor welds in compression are much safer than poor welds in tension.

Well, there seem to be countless critical welds on the world's bikes.
Someone seems willing to guarantee those welds' quality. Ditto those
on motorcycle parts, car parts, and about a million other devices. So
I think it's possible.

> > frkry...@gmail.com wrote:
>
> > That's why cantilever and V-brake
> > studs are always on the _back_ side of front forks, so they're never
> > in tension! ... oh, wait ...
>
> if they're positioned for the rim, they're subject to ~1/3rd the force!
> obviously, that makes for much less fatigue risk!!!

Yep. And if subject to triple the force, you'd need, oh, roughly
triple the cross section area to properly resist failure. I'm
simplifying a bit, but the general idea is obvious, not rocket
science. Now, triple the weight of those little lugs equals ... let's
see... ah! "Negligible."

> and if they were rear mounted, they could be lighter, stronger and
> safer!

My guess is that my cantilever mounting studs weigh about an ounce.
They can't be much lighter! And I've yet to hear of any such stud
ever failing from fatigue. Have you?

- Frank Krygowski

Date: 10 Nov 2007 23:24:41
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

frkrygow@gmail.com wrote:
> On Nov 10, 1:32 pm, jim beam <spamvor...@bad.example.net> wrote, about
> front mounted brake calipers:
>
>> can you guarantee the weld quality? because that is the point of issue.
>> poor welds in compression are much safer than poor welds in tension.
>
> Well, there seem to be countless critical welds on the world's bikes.

ya think? and which of them experience the same leverage as a disk
brake tab?

> Someone seems willing to guarantee those welds' quality. Ditto those
> on motorcycle parts, car parts, and about a million other devices. So
> I think it's possible.

of course it's "possible". but unless you're speaking from a position
of ignorance of weld metallurgy, you wouldn't claim that a tensile weld
is as safe as a compressive weld in fatigue. oh, but you just have...

>
>>> frkry...@gmail.com wrote:
>>> That's why cantilever and V-brake
>>> studs are always on the _back_ side of front forks, so they're never
>>> in tension! ... oh, wait ...
>> if they're positioned for the rim, they're subject to ~1/3rd the force!
>> obviously, that makes for much less fatigue risk!!!
>
> Yep. And if subject to triple the force, you'd need, oh, roughly
> triple the cross section area to properly resist failure. I'm
> simplifying a bit, but the general idea is obvious, not rocket
> science. Now, triple the weight of those little lugs equals ... let's
> see... ah! "Negligible."

because you can't argue the point, because it's irrefutable, you try to
wave it away as insignificant. brilliant tactic for an engineering
professor.

>
>> and if they were rear mounted, they could be lighter, stronger and
>> safer!
>
> My guess is that my cantilever mounting studs weigh about an ounce.
> They can't be much lighter! And I've yet to hear of any such stud
> ever failing from fatigue. Have you?

have ever seen a disk brake eject from a rear mounted caliper?

Date: 10 Nov 2007 16:58:24
From:
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 9, 10:45 pm, jim beam <spamvor...@bad.example.net > wrote:
> James Thomson wrote:
>
> > Cotic claim there was axle movement under heavy braking, and that's a claim
> > that others have made. Repositioning the brake mount does everything they
> > claim, and has no drawback.
>
> yes it does. it puts the tab welds under tension, not compression.
> this is guaranteed to be a greater fatigue risk than a rear mounted tab.
> that's why tabs are rear mounted in the first place!

And designers can't possibly use a couple grams more material to
reduce the fatigue risk to zero. That's why cantilever and V-brake
studs are always on the _back_ side of front forks, so they're never
in tension! Ditto for sidepull brakes' mounting bolts.

... oh, wait...

- Frank Krygowski

Date: 10 Nov 2007 10:32:23
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

frkrygow@gmail.com wrote:
> On Nov 9, 10:45 pm, jim beam <spamvor...@bad.example.net> wrote:
>> James Thomson wrote:
>>
>>> Cotic claim there was axle movement under heavy braking, and that's a claim
>>> that others have made. Repositioning the brake mount does everything they
>>> claim, and has no drawback.
>> yes it does. it puts the tab welds under tension, not compression.
>> this is guaranteed to be a greater fatigue risk than a rear mounted tab.
>> that's why tabs are rear mounted in the first place!
>
> And designers can't possibly use a couple grams more material to
> reduce the fatigue risk to zero.

can you guarantee the weld quality? because that is the point of issue.
poor welds in compression are much safer than poor welds in tension.

> That's why cantilever and V-brake
> studs are always on the _back_ side of front forks, so they're never
> in tension!

if they're positioned for the rim, they're subject to ~1/3rd the force!
obviously, that makes for much less fatigue risk!!!

> Ditto for sidepull brakes' mounting bolts.
>
> ... oh, wait...

and if they were rear mounted, they could be lighter, stronger and
safer! just like a disk brake mounting.

for a guy that presumes to teach engineering, your grasp of the basics
isn't very impressive.

Date: 14 Nov 2007 16:27:31
From: Jasper Janssen
Subject: Re: Candid comments from Cotic on disks and QRs

On Sat, 10 Nov 2007 10:32:23 -0800, jim beam <spamvortex@bad.example.net >
wrote:

>can you guarantee the weld quality? because that is the point of issue.
> poor welds in compression are much safer than poor welds in tension.

Well, as there is now a product in the market that has the welds in
tension, and has been for 18 months, we, (or at least someone) should now
have actual data to support whether or not this is an issue. Has there
been a rash of failures of these forks?

Jasper

Date: 14 Nov 2007 19:57:35
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

Jasper Janssen wrote:
> On Sat, 10 Nov 2007 10:32:23 -0800, jim beam <spamvortex@bad.example.net>
> wrote:
>
>> can you guarantee the weld quality? because that is the point of issue.
>> poor welds in compression are much safer than poor welds in tension.
>
> Well, as there is now a product in the market that has the welds in
> tension, and has been for 18 months, we, (or at least someone) should now
> have actual data to support whether or not this is an issue. Has there
> been a rash of failures of these forks?

the more rational [not rationale] question to ask would be whether they
used a rear-mounting tab and put it on the front without proper
redesign, or whether they knew what they were doing and attempted to
address the tension fatigue issue properly.

Date: 15 Nov 2007 20:07:01
From: Jasper Janssen
Subject: Re: Candid comments from Cotic on disks and QRs

On Wed, 14 Nov 2007 19:57:35 -0800, jim beam <spamvortex@bad.example.net >
wrote:
>Jasper Janssen wrote:
>> On Sat, 10 Nov 2007 10:32:23 -0800, jim beam <spamvortex@bad.example.net>
>> wrote:
>>
>>> can you guarantee the weld quality? because that is the point of issue.
>>> poor welds in compression are much safer than poor welds in tension.
>>
>> Well, as there is now a product in the market that has the welds in
>> tension, and has been for 18 months, we, (or at least someone) should now
>> have actual data to support whether or not this is an issue. Has there
>> been a rash of failures of these forks?
>
>the more rational [not rationale] question to ask would be whether they
>used a rear-mounting tab and put it on the front without proper
>redesign, or whether they knew what they were doing and attempted to
>address the tension fatigue issue properly.

They said up above in the thread that it wasn't hard to redesign the mount
for those stresses, so I would assume they'd actually done that.

Jasper

Date: 10 Nov 2007 18:16:10
From: M-gineering
Subject: Re: Candid comments from Cotic on disks and QRs

frkrygow@gmail.com wrote:
That's why cantilever and V-brake
> studs are always on the _back_ side of front forks, so they're never
> in tension!

I certainly hope that the difference of plus or minus 7-15 N/mm2 isn't
going to determine whether the studs fall off or not. The bending moment
stays the same and is the much bigger force

--
/Marten

info(apestaartje)m-gineering(punt)nl

Date: 10 Nov 2007 11:55:56
From: Tom Sherman
Subject: Re: Candid comments from Cotic on disks and QRs

M-gineering aka Marten Gerritsen wrote:
> frkrygow@gmail.com wrote:
> That's why cantilever and V-brake
>> studs are always on the _back_ side of front forks, so they're never
>> in tension!
>
> I certainly hope that the difference of plus or minus 7-15 N/mm2 isn't
> going to determine whether the studs fall off or not. The bending moment
> stays the same and is the much bigger force
>
Why not just use a single-sided wheel mount with front disc brakes and
not worry about it? ;)
<http://www.flickr.com/photos/19704682@N08/1939602865/ >.

--
Tom Sherman - Holstein-Friesland Bovinia
Tradition is the worst rational for action.

Date: 13 Nov 2007 09:41:53
From: Dave Larrington
Subject: Re: Candid comments from Cotic on disks and QRs

In news:fh4ras$1se$1@registered.motzarella.org,
Tom Sherman <sunsetss0003@REMOVETHISyahoo.com > tweaked the Babbage-Engine to
tell us:

> Why not just use a single-sided wheel mount with front disc brakes and
> not worry about it? ;)
> <http://www.flickr.com/photos/19704682@N08/1939602865/>.

Because monoblades tend not to work terribly well with full-sized wheels?

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk >
%VMS-W-IVWORD, unrecognized word "downtime" - check validity and
spelling

Date: 13 Nov 2007 20:22:23
From: Tom Sherman
Subject: Re: Candid comments from Cotic on disks and QRs

Dave Larrington wrote:
> In news:fh4ras$1se$1@registered.motzarella.org,
> Tom Sherman <sunsetss0003@REMOVETHISyahoo.com> tweaked the Babbage-Engine to
> tell us:
>
>> Why not just use a single-sided wheel mount with front disc brakes and
>> not worry about it? ;)
>> <http://www.flickr.com/photos/19704682@N08/1939602865/>.
>
>
> Because monoblades tend not to work terribly well with full-sized wheels?
>
My wheels are full sized - they form a hoop, not a crescent! ;)

M5 offers a monoblade on their ISO 571-mm wheel Shockproof:
<http://www.m5-ligfietsen.nl/site/EN/Models/Shock_Proof_571_Titanium >.

--
Tom Sherman - Holstein-Friesland Bovinia
"the grinning buddy bear carries a fork." - g.d.

Date: 13 Nov 2007 11:56:27
From: Alan Braggins
Subject: Re: Candid comments from Cotic on disks and QRs

In article <5ptb4hFsv1gpU1@mid.individual.net >, Dave Larrington wrote:
>In news:fh4ras$1se$1@registered.motzarella.org,
>Tom Sherman <sunsetss0003@REMOVETHISyahoo.com> tweaked the Babbage-Engine to
>tell us:
>
>> Why not just use a single-sided wheel mount with front disc brakes and
>> not worry about it? ;)
>> <http://www.flickr.com/photos/19704682@N08/1939602865/>.
>
>Because monoblades tend not to work terribly well with full-sized wheels?

Simon seems conviced that Cannondale Lefty style "forks" are the way of
the future. What do you know that he and Cannondale don't?

Date: 13 Nov 2007 12:30:26
From: Peter Clinch
Subject: Re: Candid comments from Cotic on disks and QRs

Alan Braggins wrote:

> Simon seems conviced that Cannondale Lefty style "forks" are the way of
> the future. What do you know that he and Cannondale don't?

I suspect /almost/ eveyone knows that 559 wheels as used on the Lefty
are smaller than the 700c that it looks like the Cotic fork is designed
for...

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/

Date: 08 Nov 2007 22:05:42
From: Tom Sherman
Subject: Re: Candid comments from Cotic on disks and QRs

james.annan@gmail.com aka James Annan wrote:
> I know their roadhog forks (with the disk mount on the front of the RH
> fork leg) have been commented on before, but their explanation for
> this design is refreshingly candid:
>
> "Axle movement under disc braking is now a fairly well known
> phenomenon in mountain biking. Basically with the caliper positioned
> left rear (usual place), and a vertical dropout, there is a reaction
> of the braking force which tends to push the axle out of the dropout,
> hence you're relying on the friction of your QR to counteract this
> rather than a completely mechanical stop. Most manufacturers have
> moved to a slightly forward facing dropout to counteract this.
>
> "We've actually never experienced any trouble with this on our
> mountain bikes, but during prototype testing of the ROADHOG fork -
> which had the disc mount in the usual left rear position - we did
> actually experience some axle movement. Nothing actually came undone,
> but after some serious downhill braking on fast roads, the rotors
> would be rubbing a touch and the wheel would 'clunk' home in the
> dropout when we undid the axle nuts. This was clearly unacceptable, so
> we set about finding a solution."
>
> <http://www.cotic.co.uk/geek/>
>
> I suppose the usual suspects will claim that this just proves that
> Cotic do not know how to use QRs...

Where is the ISO 406-mm fork?

--
Tom Sherman - Holstein-Friesland Bovinia
Tradition is the worst rational for action.

Date: 07 Nov 2007 13:34:28
From: Marz
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 6, 9:30 pm, "james.an...@gmail.com" <james.an...@gmail.com >
wrote:
> I know their roadhog forks (with the disk mount on the front of the RH
> fork leg) have been commented on before, but their explanation for
> this design is refreshingly candid:
>
> "Axle movement under disc braking is now a fairly well known
> phenomenon in mountain biking. Basically with the caliper positioned
> left rear (usual place), and a vertical dropout, there is a reaction
> of the braking force which tends to push the axle out of the dropout,
> hence you're relying on the friction of your QR to counteract this
> rather than a completely mechanical stop. Most manufacturers have
> moved to a slightly forward facing dropout to counteract this.
>
> "We've actually never experienced any trouble with this on our
> mountain bikes, but during prototype testing of the ROADHOG fork -
> which had the disc mount in the usual left rear position - we did
> actually experience some axle movement. Nothing actually came undone,
> but after some serious downhill braking on fast roads, the rotors
> would be rubbing a touch and the wheel would 'clunk' home in the
> dropout when we undid the axle nuts. This was clearly unacceptable, so
> we set about finding a solution."
>
> <http://www.cotic.co.uk/geek/>
>
> I suppose the usual suspects will claim that this just proves that
> Cotic do not know how to use QRs...
>
> James

I'd be interested to see what it is about these roadie forks compared
to mtb forks that produced this axle movement. Could it be the steeper
head tube angle, larger diameter tyres or the increased friction
between slick tyre and tarmac compared to knobbly tyre and dirt?
Still, not and never has been a problem for mtbs as Cotic say
themselves.

laters,

Marz

Date: 07 Nov 2007 03:38:10
From: CoyoteBoy
Subject: Re: Candid comments from Cotic on disks and QRs

On 7 Nov, 06:17, Michael Press <rub...@pacbell.net > wrote:
> In article
> <1194406213.024479.115...@i38g2000prf.googlegroups.com>
> ,
> "james.an...@gmail.com" <james.an...@gmail.com>
>
>
>
> wrote:
> > I know their roadhog forks (with the disk mount on the front of the RH
> > fork leg) have been commented on before, but their explanation for
> > this design is refreshingly candid:
>
> > "Axle movement under disc braking is now a fairly well known
> > phenomenon in mountain biking. Basically with the caliper positioned
> > left rear (usual place), and a vertical dropout, there is a reaction
> > of the braking force which tends to push the axle out of the dropout,
> > hence you're relying on the friction of your QR to counteract this
> > rather than a completely mechanical stop. Most manufacturers have
> > moved to a slightly forward facing dropout to counteract this.
>
> > "We've actually never experienced any trouble with this on our
> > mountain bikes, but during prototype testing of the ROADHOG fork -
> > which had the disc mount in the usual left rear position - we did
> > actually experience some axle movement. Nothing actually came undone,
> > but after some serious downhill braking on fast roads, the rotors
> > would be rubbing a touch and the wheel would 'clunk' home in the
> > dropout when we undid the axle nuts. This was clearly unacceptable, so
> > we set about finding a solution."
>
> > <http://www.cotic.co.uk/geek/>
>
> > I suppose the usual suspects will claim that this just proves that
> > Cotic do not know how to use QRs...
>
> I never thought a manufacturer would have the sand
> to obviate the problem by moving the calipers.
> Good on them. Now their competitors will have
> some explaining to do.
>

Probably the only explaining they'll do is "use your QR properly".

J (never yet had a skewer slip under braking).

Date: 07 Nov 2007 09:38:10
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <1194406213.024479.115730@i38g2000prf.googlegroups.com >,
james.annan@gmail.com says...
>
> <http://www.cotic.co.uk/geek/>
>
> I suppose the usual suspects will claim that this just proves that
> Cotic do not know how to use QRs...
>

No, but they do know how to use Marketing 101. How do you differentiate
yourself from the pack? Create a problem that only your product solves.

Meanwhile how many years on are we now and what has actually happened
during all that time? Even you haven't updated your website information
for almost two years now.

--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

Date: 15 Nov 2007 11:57:54
From: Ed Pirrero
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 15, 12:02 am, "james.an...@gmail.com" <james.an...@gmail.com >
wrote:
> On Nov 15, 12:57 pm, jim beam <spamvor...@bad.example.net> wrote:
>
>
>
> > the more rational [not rationale] question to ask would be whether they
> > used a rear-mounting tab and put it on the front without proper
> > redesign, or whether they knew what they were doing and attempted to
> > address the tension fatigue issue properly.
>
> It might also be rational to ask whether fork manufacturers changed
> from rim brakes to disk brakes without doing proper redesign of the
> wheel attachment, or whether they knew what they were doing and
> attempted to address the ejection force issue properly.
>
> Of course, Cannondale did do some testing:
>
> <http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
> cannondale.html>
>
> Hands up those who think they did
> (A) a competent job as one might expect of a major manufacturer
> (B) a laughably inadequate test which was so utterly useless that the
> person who designed it must either be grossly incompetent or
> fraudulent

Interesting, isn't it - no countering data, no experimentation done to
show that the methodology was flawed - just a flip comment that
supposed to cast doubt on the only real data collection that's been
done to date.

You sound a lot like Mike Vandeman.

E.P.

Date: 15 Nov 2007 00:02:00
From: james.annan@gmail.com
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 15, 12:57 pm, jim beam <spamvor...@bad.example.net > wrote:
>
> the more rational [not rationale] question to ask would be whether they
> used a rear-mounting tab and put it on the front without proper
> redesign, or whether they knew what they were doing and attempted to
> address the tension fatigue issue properly.

It might also be rational to ask whether fork manufacturers changed
from rim brakes to disk brakes without doing proper redesign of the
wheel attachment, or whether they knew what they were doing and
attempted to address the ejection force issue properly.

Of course, Cannondale did do some testing:

<http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
cannondale.html >

Hands up those who think they did
(A) a competent job as one might expect of a major manufacturer
(B) a laughably inadequate test which was so utterly useless that the
person who designed it must either be grossly incompetent or
fraudulent

James

Date: 15 Nov 2007 06:04:08
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

james.annan@gmail.com wrote:
> On Nov 15, 12:57 pm, jim beam <spamvor...@bad.example.net> wrote:
>> the more rational [not rationale] question to ask would be whether they
>> used a rear-mounting tab and put it on the front without proper
>> redesign, or whether they knew what they were doing and attempted to
>> address the tension fatigue issue properly.
>
> It might also be rational to ask whether fork manufacturers changed
> from rim brakes to disk brakes without doing proper redesign of the
> wheel attachment, or whether they knew what they were doing and
> attempted to address the ejection force issue properly.
>
> Of course, Cannondale did do some testing:
>
> <http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
> cannondale.html>
>
> Hands up those who think they did
> (A) a competent job as one might expect of a major manufacturer
> (B) a laughably inadequate test which was so utterly useless that the
> person who designed it must either be grossly incompetent or
> fraudulent
>

you're priceless.

disk hub axles are serrated, unlike their non-disk predecessors. this
means they need to physically shear through the metal into which they
are clamped if they are to be ejected. the force necessary to do that
exceeds "ejection" force many fold. i don't know how many more times
you need to be reminded of this before you finally start to correlate
the math with reality, but hey, you're james annan.

oh, i forgot lawyer lips. well, i didn't really, but why let the
obvious get in the way of your ability to omit any details that show you
to be such a bullshitter?

Date: 15 Nov 2007 18:29:28
From: Michael Press
Subject: Re: Candid comments from Cotic on disks and QRs

In article
<vaidncCliJ1FzKHanZ2dnUVZ_tzinZ2d@speakeasy.net >,
jim beam <spamvortex@bad.example.net > wrote:

> james.annan@gmail.com wrote:
> > On Nov 15, 12:57 pm, jim beam <spamvor...@bad.example.net> wrote:
> >> the more rational [not rationale] question to ask would be whether they
> >> used a rear-mounting tab and put it on the front without proper
> >> redesign, or whether they knew what they were doing and attempted to
> >> address the tension fatigue issue properly.
> >
> > It might also be rational to ask whether fork manufacturers changed
> > from rim brakes to disk brakes without doing proper redesign of the
> > wheel attachment, or whether they knew what they were doing and
> > attempted to address the ejection force issue properly.
> >
> > Of course, Cannondale did do some testing:
> >
> > <http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
> > cannondale.html>
> >
> > Hands up those who think they did
> > (A) a competent job as one might expect of a major manufacturer
> > (B) a laughably inadequate test which was so utterly useless that the
> > person who designed it must either be grossly incompetent or
> > fraudulent
> >
>
> you're priceless.

And a good think too, because you do not
have the price of admission.

[...]

--
Michael Press

Date: 15 Nov 2007 11:40:49
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <dcf8681a-2a31-46e5-a10c-
1141f8a12e5a@a39g2000pre.googlegroups.com >, james.annan@gmail.com
says...
>

I see the BBC now has you down as a Climate Change Sceptic ;-)
http://news.bbc.co.uk/1/hi/sci/tech/7092614.stm

--
Tony

"The single biggest problem in communication is the illusion that it has
taken place"
George Bernard Shaw

Date: 09 Nov 2007 08:55:25
From: Dave Larrington
Subject: Re: Candid comments from Cotic on disks and QRs

In news:MPG.219b947f3082b270989884@news.nildram.co.uk,
Tony Raven <junk@raven-family.invalid > tweaked the Babbage-Engine to tell
us:

> No, but they do know how to use Marketing 101. How do you
> differentiate yourself from the pack? Create a problem that only
> your product solves.

Can't see what all the fuss is about, me. Since the Roadhog fork has no
disadvantages over the "conventional" layout and at least one advantage (see
comment re mudguards upthread) I'd say that Cy Cotic is to be applauded.

Disclaimer: I have a disc-equipped Roadrat, but don't use a q/r on the front
wheel coz I don't want the pikeys to make off with my SON.

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk >
Never give a gun to ducks.

Date: 09 Nov 2007 12:04:41
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <5pilnqFqt7mgU1@mid.individual.net >,
smert.spamionam@privacy.net says...
> In news:MPG.219b947f3082b270989884@news.nildram.co.uk,
> Tony Raven <junk@raven-family.invalid> tweaked the Babbage-Engine to tell
> us:
>
> > No, but they do know how to use Marketing 101. How do you
> > differentiate yourself from the pack? Create a problem that only
> > your product solves.
>
> Can't see what all the fuss is about, me. Since the Roadhog fork has no
> disadvantages over the "conventional" layout and at least one advantage (see
> comment re mudguards upthread) I'd say that Cy Cotic is to be applauded.
>

Don't disagree that there may be other benefits but I doubt the disk
brake issue was the real driver behind it - if it were he would have
launched it with lots of publicity three years ago when the topic was
current. I presume since James has only just posted it that it has been
launched recently when the topic is essentially dead. Given that it
seems to be designed for the Roadrat bike, mudguards seem a far more
likely explanation with the rest just marketing fluff.

--
Tony

"The single biggest problem in communication is the illusion that it has
taken place"
George Bernard Shaw

Date: 09 Nov 2007 15:26:52
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

"Tony Raven" <junk@raven-family.invalid > a �crit:

> Don't disagree that there may be other benefits but I doubt
> the disk brake issue was the real driver behind it - if it were
> he would have launched it with lots of publicity three years
> ago when the topic was current. I presume since James
> has only just posted it that it has been launched recently
> when the topic is essentially dead. Given that it seems to
> be designed for the Roadrat bike, mudguards seem a far
> more likely explanation with the rest just marketing fluff.

I don't know much about marketing, but it seems to me that the way to make
hay from a of fear of wheel ejection would be to launch the product with
lots of publicity at a time when the topic was current.

However, the Roadrat wasn't in production when disk wheel ejection first
became a hot topic (Russel Pinder's accident and James Annan's tandem wheel
ejection), so it wouldn't have been possible to produce a fork for it at
that time. But the issue would have been known to the owner of Cotic through
the Singletrack website.

Early pictures of the Roadrat showed a conventional brake mounting on the
rear of the left fork blade, consistent with the account on the Cotic
website.

This account seems quite reasonable to me:

http://www.cotic.co.uk/geek/#ROADHOG_discmount

Conclusion

The front right disc mount position solved a number of problems
we were faced with during the design phase:

Disc forces contained
IS disc mount
Full length mudguards always usable
Standard QR compatible dropout retained

Which gives you a fantastically versatile fork with no drawbacks.

James Thomson

Date: 09 Nov 2007 14:46:31
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <47346e3a$0$16708$79c14f64@nan-newsreader-05.noos.net >,
yosnappyj@hotmail.com says...
>
> I don't know much about marketing, but it seems to me that the way to make
> hay from a of fear of wheel ejection would be to launch the product with
> lots of publicity at a time when the topic was current.
>

Precisely. If they thought it important they would have launched one
three years ago with lots of hoopla. But they didn't. Which implies
that they were designing a road bike needing mudguards which, as noted,
are difficult to mount with a caliper in the way. Having done that in
marketing you look around for other "features" you can promote and
someone remembered disc brake ejection and threw it in the pot.

> However, the Roadrat wasn't in production when disk wheel ejection first
> became a hot topic (Russel Pinder's accident and James Annan's tandem wheel
> ejection), so it wouldn't have been possible to produce a fork for it at
> that time. But the issue would have been known to the owner of Cotic through
> the Singletrack website.

So is the Roadrat the only bike Cotic have produced? If not why have
they not thought to put the same design on all the other bikes starting
when the topic became hot. Why wait until recently and a road, not a
mountain, bike? After all they've been going since 2002 and their disc
braked mountain bikes don't have this feature AFAIK.

>
> Early pictures of the Roadrat showed a conventional brake mounting on the
> rear of the left fork blade, consistent with the account on the Cotic
> website.

So why do you think they changed it? For a problem that they had known
about for years and done nothing about till then or because they found
problems putting the mudguards on?
>
> This account seems quite reasonable to me:
>

Seems more like a post hoc rationalisation to me.

--
Tony

"Reality is a crutch for people who can't cope with drugs."
--Lily Tomlin

Date: 09 Nov 2007 16:29:14
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

>> I don't know much about marketing, but it seems to me that the way
>> to make hay from a of fear of wheel ejection would be to launch the
>> product with lots of publicity at a time when the topic was current.

"Tony Raven" <junk@raven-family.invalid > a �crit:

> Precisely.

Uh...

> If they thought it important they would have launched one
> three years ago with lots of hoopla. But they didn't. Which implies
> that they were designing a road bike needing mudguards which, as noted,
> are difficult to mount with a caliper in the way. Having done that in
> marketing you look around for other "features" you can promote and
> someone remembered disc brake ejection and threw it in the pot.

I see - stealth marketing. Very cunning.

You must see that you could interpret either action to suit your position.
The immediate introduction of a modified fork would be exploiting public
hysteria over a problem you say doesn't exist. An explanation tucked away on
a "geek" web page long after the product launch is "marketing fluff".

> So is the Roadrat the only bike Cotic have produced?

No.

> If not why have they not thought to put the same design on all the
> other bikes starting when the topic became hot. Why wait until
> recently and a road, not a mountain, bike? After all they've been
> going since 2002 and their disc braked mountain bikes don't have
> this feature AFAIK.

They don't manufacture a fork for their other bikes, silly. Cotic's mountain
bikes are designed around long-travel suspension forks. The only fork in the
Cotic range is the Roadhog, which is only available with a Roadrat frame,
which - as I pointed out previously - was introduced 18 months ago.

> So why do you think they changed it? For a problem that they
> had known about for years and done nothing about till then or
> because they found problems putting the mudguards on?

As I wrote, I think their explanation is consistent with the facts as
they're known. The prototype was made with a standard caliper mount:

http://www.cotic.co.uk/news/photos/cycleshow2005/open.jpg

Cotic claim there was axle movement under heavy braking, and that's a claim
that others have made. Repositioning the brake mount does everything they
claim, and has no drawback.

James Thomson

Date: 09 Nov 2007 19:45:08
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

James Thomson wrote:
>>> I don't know much about marketing, but it seems to me that the way
>>> to make hay from a of fear of wheel ejection would be to launch the
>>> product with lots of publicity at a time when the topic was current.
>
> "Tony Raven" <junk@raven-family.invalid> a �crit:
>
>> Precisely.
>
> Uh...
>
>> If they thought it important they would have launched one
>> three years ago with lots of hoopla. But they didn't. Which implies
>> that they were designing a road bike needing mudguards which, as noted,
>> are difficult to mount with a caliper in the way. Having done that in
>> marketing you look around for other "features" you can promote and
>> someone remembered disc brake ejection and threw it in the pot.
>
> I see - stealth marketing. Very cunning.
>
> You must see that you could interpret either action to suit your position.
> The immediate introduction of a modified fork would be exploiting public
> hysteria over a problem you say doesn't exist. An explanation tucked away on
> a "geek" web page long after the product launch is "marketing fluff".
>
>> So is the Roadrat the only bike Cotic have produced?
>
> No.
>
>> If not why have they not thought to put the same design on all the
>> other bikes starting when the topic became hot. Why wait until
>> recently and a road, not a mountain, bike? After all they've been
>> going since 2002 and their disc braked mountain bikes don't have
>> this feature AFAIK.
>
> They don't manufacture a fork for their other bikes, silly. Cotic's mountain
> bikes are designed around long-travel suspension forks. The only fork in the
> Cotic range is the Roadhog, which is only available with a Roadrat frame,
> which - as I pointed out previously - was introduced 18 months ago.
>
>> So why do you think they changed it? For a problem that they
>> had known about for years and done nothing about till then or
>> because they found problems putting the mudguards on?
>
> As I wrote, I think their explanation is consistent with the facts as
> they're known. The prototype was made with a standard caliper mount:
>
> http://www.cotic.co.uk/news/photos/cycleshow2005/open.jpg
>
> Cotic claim there was axle movement under heavy braking, and that's a claim
> that others have made. Repositioning the brake mount does everything they
> claim, and has no drawback.

yes it does. it puts the tab welds under tension, not compression.
this is guaranteed to be a greater fatigue risk than a rear mounted tab.
that's why tabs are rear mounted in the first place!

Date: 09 Nov 2007 20:58:09
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <47347cd8$0$32258$79c14f64@nan-newsreader-06.noos.net >,
yosnappyj@hotmail.com says...
>
> I see - stealth marketing. Very cunning.
>

Hardly - as I said, Marketing 101. Go and read a few ski adverts to see
something very similar in action. And the rest of their site is hardly
short on marketing speak: "A super low toptube keep the ride tight and
chuckable, and a massively oversized downtube keeps both wheels pointing
in the right direction for maximum handling confidence."

> You must see that you could interpret either action to suit your position.
> The immediate introduction of a modified fork would be exploiting public
> hysteria over a problem you say doesn't exist.

Well either you believe its a serious problem that needs an immediate
solution or you don't in which case you can introduce it at leisure 2
years later when the hubbub has all died down and use "the problem" to
help with the marketing. Which one do you think it is?

>
> They don't manufacture a fork for their other bikes, silly. Cotic's mountain
> bikes are designed around long-travel suspension forks. The only fork in the
> Cotic range is the Roadhog, which is only available with a Roadrat frame,
> which - as I pointed out previously - was introduced 18 months ago.
>

So that would be why they sell their Soda Frame with a Pace rigid fork
with the disc mount in the standard position and vertical drop outs
rather than with their own fork with its special safety feature then.
http://www.cotic.co.uk/product/soda.html

>
> Cotic claim there was axle movement under heavy braking, and that's a claim
> that others have made. Repositioning the brake mount does everything they
> claim, and has no drawback.
>

Yes but we are discussing the reason they did it and as I say I bet it
was the mudguard mounting and nothing to do with the disc forces or they
would not be selling the Pace Rigid fork on their mountain bikes (which
don't need mounting points for the mudguard stays)

--
Tony

"The single biggest problem in communication is the illusion that it has
taken place"
George Bernard Shaw

Date: 12 Nov 2007 09:53:24
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

"Tony Raven" <junk@raven-family.invalid > a �crit:

> Marketing 101. Go and read a few ski adverts to
> see something very similar in action.

I'm not really interested in skiing, but if you come up with an example you
think is analogous I'll consider it.

Bear in mind though that even if you can show that ski manufacturers invent
similar claims, that only proves that ski manufacturers invent similar
claims, not that this claim is invented.

> And the rest of their site is hardly short on marketing speak:
> "A super low toptube keep the ride tight and chuckable, and
> a massively oversized downtube keeps both wheels pointing
> in the right direction for maximum handling confidence."

I think that's what young people say these days when they mean "agile" and
"torsionally stiff" - it's probably what comes of growing up on a diet of
MBUK. But those are just subjective claims about the handling of the
bicycle, the like of which are to be found on the websites of most
manufacturers.

The claims about the Roadhog fork are rather different. They're fairly
detailed, factually coherent, conveyed in reasonably sober language, and
claim an actual experience of axle movement. If you believe the account is
truthful, the adoption of a forward-facing disk mount on the Roadhog fork
makes perfect sense.

> either you believe its a serious problem that needs an immediate
> solution or you don't in which case you can introduce it at leisure 2
> years later when the hubbub has all died down and use "the problem"
> to help with the marketing. Which one do you think it is?

A false dichotomy, obviously.

If Cotic had been in the business of making mountain bike forks, then it
would be strange if they claimed to have experienced axle movement but
continued to manufacture a fork with a rear-left disk mount. As it is, they
claim to have experienced axle movement only on their prototype road fork,
and photographic evidence shows that the disk mount position was changed
between the prototype and the production run. The only production fork that
Cotic has manufactured has a right-front disk mount.

>> Cotic's mountain bikes are designed around long-travel suspension
>> forks. The only fork in the Cotic range is the Roadhog, which is only
>> available with a Roadrat frame, which - as I pointed out previously -
>> was introduced 18 months ago.

> So that would be why they sell their Soda Frame with a Pace rigid
> fork with the disc mount in the standard position and vertical drop
> outs rather than with their own fork with its special safety feature then.
> http://www.cotic.co.uk/product/soda.html

In a sense, yes.

Cotic's mountain bikes are designed around long-travel suspension forks.
Cotic's raison d'�tre was to produce a premium quality steel hardtail
compatible with 100-125mm travel suspension forks. Cotic has never produced
a mountain bike fork of any description, in fact excluding the
Roadrat/Roadhog, Cotic's only offerings have been mountain frames, the
business model being that the customer will buy a bare frame and choose his
own fork and other components.

They have, at various times, had deals with component manufacturers (USE,
Hope, and Pace, for example) so that a Cotic customer could purchase a fork,
headset, brakes etc. with the frame for a package price, but they haven't
offered complete assembled bikes, again with the exception of the Roadrat.

Although Cotic's mountain bike geometry is designed around a long-travel
suspension fork, some fraction of the client�le may want to use a rigid
fork, and Pace's RC31 is made in a 440mm version, suitable for a frame
designed around a long-travel suspension fork. Cotic normally offer Pace
suspension forks as an option with a frame purchase. They don't currently
have stock of the suspension models because the business has recently
changed premises and was running down its stocks prior to the move and prior
to the release of the 2008 fork models, as explained on the Cotic website:

http://www.cotic.co.uk/news/

The only fork left in stock is the RC31.

>> Repositioning the brake mount does everything
>> they claim, and has no drawback.

> Yes but we are discussing the reason they did it and as I say
> I bet it was the mudguard mounting and nothing to do with the
> disc forces or they would not be selling the Pace Rigid fork on
> their mountain bikes (which don't need mounting points for the
> mudguard stays)

That doesn't follow. Cotic has never manufactured a mountain bike fork.
They may well consider that a front-right disk mount is advantageous from
the point of view of the reduced risk of axle movement, but they also have a
contract with Pace, and a product range skewed towards long travel
suspension. I doubt that they have the resources to develop a competitive
suspension fork, and I doubt it's ever been commercially interesting for
them to move into rigid fork production for their off-road range when those
frames are specifically designed and marketed as long-travel XC hardtails.

I think I'm going to drop Cotic a line and ask for clarification of a couple
of points. Before I do, could you clarify whether you think their account of
axle movement on the Roadrat prototype is actually fabricated, or just a
false justification for their Roadhog fork design?

James Thomson

Date: 14 Nov 2007 16:04:04
From:
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 14, 10:40 am, Jasper Janssen <jas...@jjanssen.org > wrote:
> On Wed, 14 Nov 2007 08:55:48 -0000, Mark McNeill
>
> <markonnewsgro...@yahoo.co.uk> wrote:
> >It's tempting to infer that the much smaller and lower-torque nylocks
> >used in skewers are subject to a similar type of degradation in
> >performance. Does anybody know? And where nylocks undergo
> >tightening/loosening cycles in critical applications in industry, do
> >they come with recommendations for their regular replacement?
>
> In aircraft, I believe Nylocks cannot be reused at all.
>
> There are nylocks in skewers? I'd never noticed..
>

There is a nylon locking mechanism in skewers, but it doesn't qualify
as equivalent to a nylock nut.

In one of the previous incarnations of this debate, I did torque
measurements of a standard commercial nylock nut, and compared to
measurements of a QR nut. I won't dig back to find my numbers, but
the difference was extreme, with the QR nut being much, much weaker.
Think about it! You easily twist the QR nut with your fingers!

The function of a standard nylon insert in a nylock is to prevent
rotation of the nut under conditions of significant, strong lateral
vibration. They work pretty well (at least, for one-time use). The
function of the nylon insert in a QR nut is just to hold your
adjustment for a few seconds while you tighten the clamping lever.
They are NOT the same.

Again, the QR nut's nylon lock is purposely much, much weaker. If
skewers had true nylock nuts to hold their adjustment, they'd need
wrenches to change the adjustment. And at that point, you may as well
use a solid, nutted axle.

- Frank Krygowski

Date: 12 Nov 2007 10:03:22
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <473815a0$0$23563$79c14f64@nan-newsreader-05.noos.net >,
yosnappyj@hotmail.com says...
> That doesn't follow. Cotic has never manufactured a mountain bike fork.
> They may well consider that a front-right disk mount is advantageous from
> the point of view of the reduced risk of axle movement, but they also have a
> contract with Pace, and a product range skewed towards long travel
> suspension. I doubt that they have the resources to develop a competitive
> suspension fork, and I doubt it's ever been commercially interesting for
> them to move into rigid fork production for their off-road range when those
> frames are specifically designed and marketed as long-travel XC hardtails.
>

So what you are saying is they don't see it as a significant enough
problem to do anything about on the sort of bikes for which the problems
have allegedly arisen in real life and the majority of bikes they sell.
I see.

> I think I'm going to drop Cotic a line and ask for clarification of a couple
> of points. Before I do, could you clarify whether you think their account of
> axle movement on the Roadrat prototype is actually fabricated, or just a
> false justification for their Roadhog fork design?
>

Most marketing claims have some tenuous link with reality but they admit
that its not a problem they have ever seen on the mountain bikes. What
therefore happened on their road bike is open to question. What is
clear is they sell lots of bikes without mudguards and with rigid and
suspension forks for which they have done nothing and they sell one bike
with mudguards for which they have seen the need to do something. I
think that speaks for itself - YMMV

Incidentally did the original with the caliper on the back have
mudguards fitted?

--
Tony

"Man is a credulous animal, and must believe something; in the absence
of good grounds for belief, he will be satisfied with bad ones."
- Bertrand Russell

Date: 12 Nov 2007 12:28:22
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

"Tony Raven" <junk@raven-family.invalid > a �crit:

> So what you are saying is they don't see it as a significant
> enough problem to do anything about on the sort of bikes for
> which the problems have allegedly arisen in real life and the
> majority of bikes they sell.

I'm clearly saying that Cotic is a tiny company with limited resources,
whose commercial priorities clearly do not lie in fork manufacture. You seem
to think they operate in a commercial vacuum.

>> I think I'm going to drop Cotic a line and ask for clarification of a
>> couple of points. Before I do, could you clarify whether you think
>> their account of axle movement on the Roadrat prototype is actually
>> fabricated, or just a false justification for their Roadhog fork design?

> Most marketing claims have some tenuous link with reality but
> they admit that its not a problem they have ever seen on the mountain
> bikes. What therefore happened on their road bike is open to
> question.

Everything is open to question. Do you believe their account of axle
movement or not?

> What is clear is they sell lots of bikes without mudguards and
> with rigid and suspension forks for which they have done nothing
> and they sell one bike with mudguards for which they have seen
> the need to do something.

What is clear is that they manufacture (I use the term loosely - the design
is Cotic's, the fabrication is done elsewhere) one fork with a front-right
disk mount, and sell third party forks with conventional disk mounts. Doing
something in the latter case would involve either manufacturing their own
range of forks (for which I doubt they have the resources, or in the case of
a rigid fork, a reasonable customer base), bringing pressure to bear on
their fork supplier (which, given the relative sizes of Pace and Cotic,
isn't realistic) or only selling through-axle or similar forks (which would
limit what is probably an important revenue source for the company).

They may feel that the problem is limited in scope.

They may feel that this is a problem for fork, brake, and hub manufacturers
to address.

I'll ask.

> Incidentally did the original with the caliper on the
> back have mudguards fitted?

Before - no muguards:

http://www.cotic.co.uk/product/interface/roadrat/gallery/mainpic_01.jpg

After - no mudguards:

http://www.cotic.co.uk/product/interface/roadrat/gallery/mainpic_09.jpg

James Thomson

Date: 12 Nov 2007 12:37:46
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <473838df$0$23972$79c14f64@nan-newsreader-07.noos.net >,=20
yosnappyj@hotmail.com says...
> "Tony Raven" <junk@raven-family.invalid> a =E9crit:
>=20
> > So what you are saying is they don't see it as a significant
> > enough problem to do anything about on the sort of bikes for
> > which the problems have allegedly arisen in real life and the
> > majority of bikes they sell.
>=20
> I'm clearly saying that Cotic is a tiny company with limited resources,=
=20
> whose commercial priorities clearly do not lie in fork manufacture. You s=
eem=20
> to think they operate in a commercial vacuum.
>=20
> >> I think I'm going to drop Cotic a line and ask for clarification of a
> >> couple of points. Before I do, could you clarify whether you think
> >> their account of axle movement on the Roadrat prototype is actually
> >> fabricated, or just a false justification for their Roadhog fork desig=
n?
>=20
> > Most marketing claims have some tenuous link with reality but
> > they admit that its not a problem they have ever seen on the mountain
> > bikes. What therefore happened on their road bike is open to
> > question.
>=20
> Everything is open to question. Do you believe their account of axle
> movement or not?
>=20
> > What is clear is they sell lots of bikes without mudguards and
> > with rigid and suspension forks for which they have done nothing
> > and they sell one bike with mudguards for which they have seen
> > the need to do something.
>=20
> ... or only selling through-axle or similar forks (which would
> limit what is probably an important revenue source for the company).
>=20

Which I think sums up what I am saying. If its an important safety=20
issue then the revenue (unless they were completely unscrupulous) would=20
not matter in getting it right. Indeed they spend chunks of their=20
website explaining how they use steel that is five times the price of=20
normal steel and make their own dropouts at great expense because its=20
important. But clearly they think the disc brake problem is not=20
important enough to warrant extra cost on their other bikes. They did=20
curiously though find the money to develop their own road fork (there=20
are plenty out there they could have used).

> They may feel that the problem is limited in scope.
>=20
> They may feel that this is a problem for fork, brake, and hub manufacture=
rs
> to address.
>=20
> I'll ask.
>=20
> > Incidentally did the original with the caliper on the
> > back have mudguards fitted?
>=20
> Before - no muguards:

... and rear mounted disc brake.

>=20
> After - no mudguards:
>=20

...and no disc brake; rim brakes instead.

--=20
Tony

"The single biggest problem in communication is the illusion that it has=20
taken place"=20
George Bernard Shaw

Date: 12 Nov 2007 14:41:17
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

"Tony Raven" <junk@raven-family.invalid > a �crit:

> If its an important safety issue then the revenue (unless they were
> completely unscrupulous) would not matter in getting it right. Indeed
> they spend chunks of their website explaining how they use steel
> that is five times the price of normal steel and make their own
> dropouts at great expense because its important.

As far as I know, Cotic have never claimed that this is an important safety
issue. They claim to have detected a small amount of axle movement on their
prototype Roadhog fork, and changed the design accordingly. *I* think it's
an important safety issue, but they may not. Or they may feel that it's an
important safety issue that they're not in a strong position to fix if the
result of trying is simply to send business elsewhere. That's not
unscrupulous - it's pragmatic - but in the latter case I would expect to see
a note to that effect on their site.

I'll ask.

> But clearly they think the disc brake problem is not
> important enough to warrant extra cost on their other
> bikes.

They don't sell other bikes. They sell frames, and third party forks.

>> They may feel that the problem is limited in scope.

>> They may feel that this is a problem for fork, brake, and hub
>> manufacturers to address.

>> I'll ask.

> They did curiously though find the money to develop their own
> road fork (there are plenty out there they could have used).

In fact there aren't. The Roadhog fork is unusual in having both 700c
V-brake and disk brake mounts. The design basis for the bike is described on
the Cotic site. Another fork could have been modified to suit, but it's
clearly better to design a rigid frame and its fork together. The design
costs of such a fork are minimal.

It's also *far* cheaper to design a rigid fork than to develop a suspension
fork (and not merely a question of cost, but of ability), and Soul, Soda,
and Simple mtb frames are *explicitly* sold as *long* *travel* *hardtails*.

Cotic sell one rigid fork with every Roadrat. I don't know what proportion
of their mtb customers buy a Pace rigid fork from them.

I'll ask.

>>> Incidentally did the original with the caliper on the
>>> back have mudguards fitted?

>> Before - no muguards:

> ... and rear mounted disc brake.

>> After - no mudguards:

> ...and no disc brake; rim brakes instead.

Indeed - no derailleurs either. What's your point?

And here's that question again:

>> Do you believe their account of axle movement or not?

James Thomson

Date: 13 Nov 2007 22:56:25
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

>> I'll ask.

To: <cy@cotic.co.uk >
Subject: Roadog Fork

Hi,

I'm currently involved in a discussion posted to newsgroups uk.rec.cycling
and rec.bicycles.tech that was prompted by your Roadhog fork and the
description of axle movement under heavy braking that you posted to your
website.

Naturally, this is a discussion with a considerable amount of history, and
strong opinions on both sides.

Rather than try to summarize the various arguments and risk misrepresenting
them, perhaps the simplest approach is to provide a link to the discussion
and invite you to join in.

http://groups.google.com/group/uk.rec.cycling/browse_frm/thread/f70696a8e6ac38ea?hl=en

or

http://tinyurl.com/2lxwhh

As the producer of (as far as I know) the only fork with a front-right disk
mount currently on the market, your input would be very valuable.

Best regards,

James Thomson

Date: 13 Nov 2007 22:58:47
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

From: "cy@cotic"
Re: Roadhog Fork

James,

I tried wading through some of that, and whilst I appreciate you fighting my
corner, the other guy clearly just wants to argue. All I know is that I'm
happy that everything on my website is the truth, and that as an engineer by
training I'm about the least 'marketing' person I know (much to the
irritation of my creative guys!). In terms of the basis on the argument
you're having, I did expeience axle movement on the prototype forks. Simple
fact. I've never experienced it on mountain bike forks, to which I
attribute the differing environments of stopping. On the road you can get
very long, very consisitent and sustained braking effort. Most MTB forks
have forward facing dropouts or bolt through axles these days anyway.

The only omission from the list of reasons why the mount ended up there is
also that our fork factory at the time wanted to charge an unreasonable
amount for forward facing dropouts, but bizarrely would put the disc mount
wherever we wanted for no extra charge. So, the axle movement issue,
combined with the mudguard access and the commercial pressure resulted in
that design. BTW, I was using bolt up axle skewers, not QR's, during
testing.

Cheers,

Cy
www.cotic.co.uk

Date: 13 Nov 2007 23:00:51
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

To: cy@cotic
Subject: Re: Roadhog Fork

Thanks for the quick response. I appreciate that these things tend to go
round in circles, and you have other demands on your time.

It seems to me though that there are some points you could usefully
address - the question of fatigue in the mount and caliper under tension
seems valid, for example.

If I can't persuade you to join in, do you mind if I post your reply to the
thread?

Best regards,

James Thomson

Date: 13 Nov 2007 23:02:51
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

From: "cy@cotic"
Subject: RE: Roadhog Fork

> Thanks for the quick response. I appreciate that these things tend
> to go round in circles, and you have other demands on your time.

Indeed!

> It seems to me though that there are some points you could
> usefully address - the question of fatigue in the mount and
> caliper under tension seems valid, for example.

It is a different fatigue environment, but in terms of the mount it's simply
a matter of understanding that and designing appropriately. The caliper
isn't in tension, it's simply loaded in the opposite direction that is usual
through the same load transfer mechanism. We've not had any trouble, and
it's certainly not the first brake mounting to load the caliper in this
direction (the original Santa Cruz Chameleon rear mount, for example).

> If I can't persuade you to join in, do you mind if I post your
> reply to the thread?

Feel free.

Cheers,

Cy
www.cotic.co.uk

Date: 12 Nov 2007 10:33:40
From: Peter Clinch
Subject: Re: Candid comments from Cotic on disks and QRs

Tony Raven wrote:

> Most marketing claims have some tenuous link with reality but they admit
> that its not a problem they have ever seen on the mountain bikes.

It's not a problem if you do up your QRs properly, and gravity tends to
work against wheel ejection too. OTOH, why not have a system that fails
safe, rather than unsafe, if you /don't/ do up your QRs properly?

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/

Date: 12 Nov 2007 14:59:23
From: Michael Press
Subject: Re: Candid comments from Cotic on disks and QRs

In article <5pqoi2Fsn4moU1@mid.individual.net >,
Peter Clinch <p.j.clinch@dundee.ac.uk > wrote:

> Tony Raven wrote:
>
> > Most marketing claims have some tenuous link with reality but they admit
> > that its not a problem they have ever seen on the mountain bikes.
>
> It's not a problem if you do up your QRs properly, and gravity tends to
> work against wheel ejection too. OTOH, why not have a system that fails
> safe, rather than unsafe, if you /don't/ do up your QRs properly?

The reaction force can loosen even a properly tightened
quick release nut. The quick release nut can only
loosen, never tighten. In a configuration with no disc
brake all forces are in one direction. The addition of
intermittent forces outward can "walk out" the quick
release nut. This is not theoretical. People have
reported loose quick release nuts at the bottom of a
run that the know were tight at the top of the run.

--
Michael Press

Date: 12 Nov 2007 20:27:42
From: Tom Sherman
Subject: Re: Candid comments from Cotic on disks and QRs

Michael Press wrote:
> In article <5pqoi2Fsn4moU1@mid.individual.net>,
> Peter Clinch <p.j.clinch@dundee.ac.uk> wrote:
>
>> Tony Raven wrote:
>>
>>> Most marketing claims have some tenuous link with reality but they admit
>>> that its not a problem they have ever seen on the mountain bikes.
>> It's not a problem if you do up your QRs properly, and gravity tends to
>> work against wheel ejection too. OTOH, why not have a system that fails
>> safe, rather than unsafe, if you /don't/ do up your QRs properly?
>
> The reaction force can loosen even a properly tightened
> quick release nut. The quick release nut can only
> loosen, never tighten. In a configuration with no disc
> brake all forces are in one direction. The addition of
> intermittent forces outward can "walk out" the quick
> release nut. This is not theoretical. People have
> reported loose quick release nuts at the bottom of a
> run that the know were tight at the top of the run.
>
The resistance to the idea that disc brake forces could loosen a quick
release appears to be faith based.

--
Tom "Only single-sided mount disc brake hubs" Sherman
"the grinning buddy bear carries a fork." - g.d.

Date: 12 Nov 2007 11:48:19
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <5pqoi2Fsn4moU1@mid.individual.net >, p.j.clinch@dundee.ac.uk
says...
> Tony Raven wrote:
>
> > Most marketing claims have some tenuous link with reality but they admit
> > that its not a problem they have ever seen on the mountain bikes.
>
> It's not a problem if you do up your QRs properly, and gravity tends to
> work against wheel ejection too. OTOH, why not have a system that fails
> safe, rather than unsafe, if you /don't/ do up your QRs properly?
>

That's a different discussion. The question being debated is whether
that was the fundamental reason they did it (but didn't bother on any of
their other bikes) or whether it was a bit of added marketing fluff
having already decided they needed to do it to fit the mudguard stays to
the fork. What was the cause and what was incidental?

--
Tony

"The single biggest problem in communication is the illusion that it has
taken place"
George Bernard Shaw

Date: 12 Nov 2007 12:28:30
From: Peter Clinch
Subject: Re: Candid comments from Cotic on disks and QRs

Tony Raven wrote:

> That's a different discussion. The question being debated is whether
> that was the fundamental reason they did it (but didn't bother on any of
> their other bikes) or whether it was a bit of added marketing fluff
> having already decided they needed to do it to fit the mudguard stays to
> the fork. What was the cause and what was incidental?

Since you don't actually know (especially as this seems to be their only
fork) it seems pretty unsafe to come down to one conclusion because it
happens to fit your personal thoughts on the matter.

You don't seem to have considered the possibility that it might have
been a combination of reasons. We don't know, and without looking
inside the mind of the designer(s) we won't.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/

Date: 12 Nov 2007 15:24:18
From: Tony Raven
Subject: Re: Candid comments from Cotic on disks and QRs

In article <5pqv9dFsn1anU1@mid.individual.net >, p.j.clinch@dundee.ac.uk
says...
>
> Since you don't actually know (especially as this seems to be their only
> fork) it seems pretty unsafe to come down to one conclusion because it
> happens to fit your personal thoughts on the matter.
>
> You don't seem to have considered the possibility that it might have
> been a combination of reasons. We don't know, and without looking
> inside the mind of the designer(s) we won't.
>

I think you have missed out that you can get insight into the mind by
looking at patterns of behaviour such as whether they tackled the
problem elsewhere in their range. The fact they haven't tends to
indicate they don't really see it as much of a problem. People are
willing enough to offer detailed insights here into the minds of
motorists based on patterns of behaviour ;-)

Yes, there may be multiple reasons with hindsight but usually there is a
single triggering event that leads you to change a design away from the
established standard. You then hang other rationalisations around it to
strengthen the case.

Whatever it is though they clearly don't see it as significant enough to
bother with on their other bikes.

--
Tony

"The single biggest problem in communication is the illusion that it has
taken place"
George Bernard Shaw

Date: 12 Nov 2007 15:29:00
From: Peter Clinch
Subject: Re: Candid comments from Cotic on disks and QRs

Tony Raven wrote:
>
> I think you have missed out that you can get insight into the mind by
> looking at patterns of behaviour such as whether they tackled the
> problem elsewhere in their range.

Their fork range, as I understand from James' postings, consists of this
product and no other. If that's the case then it's a meaningless point.

> The fact they haven't tends to
> indicate they don't really see it as much of a problem.

Yet they bothered changing from the prototype, which was as much as a
"range" as they had AIUI.

> Whatever it is though they clearly don't see it as significant enough to
> bother with on their other bikes.

Have you actually bothered reading James' postings on the products they
make?

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/

Date: 09 Nov 2007 15:22:32
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

"Tony Raven" <junk@raven-family.invalid > a �crit:

> Don't disagree that there may be other benefits but I doubt
> the disk brake issue was the real driver behind it - if it were
> he would have launched it with lots of publicity three years
> ago when the topic was current. I presume since James
> has only just posted it that it has been launched recently
> when the topic is essentially dead. Given that it seems to
> be designed for the Roadrat bike, mudguards seem a far
> more likely explanation with the rest just marketing fluff.

I don't know much about marketing, but it seems to me that the way to make
hay from a of fear of wheel ejection would be to launch the product with
lots of publicity at a time when the topic was current.

However, the Roadrat wasn't in production when disk wheel ejection first
became a hot topic (Russel Pinder's accident and James Annan's wheel tandem
wheel ejection), so it wouldn't have been possible to produce a fork for it
at that time. But the issue would have been known to the owner of Cotic
through the Singletrack website.

Early pictures of the Roadrat showed a conventional brake mounting on the
rear of the left fork blade, consistent with the account on the Cotic
website.

This account seems quite reasonable to me:

http://www.cotic.co.uk/geek/#ROADHOG_discmount

Conclusion

The front right disc mount position solved a number of problems
we were faced with during the design phase:
a.. Disc forces contained
b.. IS disc mount
c.. Full length mudguards always usable
d.. Standard QR compatible dropout retained
Which gives you a fantastically versatile fork with no drawbacks.

James Thomson

Date: 14 Nov 2007 16:20:06
From: Jasper Janssen
Subject: Re: Candid comments from Cotic on disks and QRs

On Fri, 9 Nov 2007 15:22:32 +0100, "James Thomson" <yosnappyj@hotmail.com >
wrote:

>I don't know much about marketing, but it seems to me that the way to make
>hay from a of fear of wheel ejection would be to launch the product with
>lots of publicity at a time when the topic was current.

Was it ever a 'hot topic' outside of rbt? Which, let's face it, isn't
nearly large enough to have any influence whatsoever on manufacturers.

Jasper

Date: 14 Nov 2007 19:10:59
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

"Jasper Janssen" <jasper@jjanssen.org > a �crit:

> Was it ever a 'hot topic' outside of rbt? Which, let's face it,
> isn't nearly large enough to have any influence whatsoever
> on manufacturers.

The issue was known to the UK-based online magazines (Bikemagic,
Singletrackworld, Bikebiz), and the online community is an important source
of sales for small, web-based companies like Cotic.

James Thomson

Date: 09 Nov 2007 13:46:57
From: James Thomson
Subject: Re: Candid comments from Cotic on disks and QRs

"Tony Raven" <junk@raven-family.invalid > a �crit:

> Don't disagree that there may be other benefits but I doubt the
> disk brake issue was the real driver behind it - if it were he
> would have launched it with lots of publicity three years ago
> when the topic was current. I presume since James has only
> just posted it that it has been launched recently when the topic
> is essentially dead.

The Roadrat was launched about 18 months ago:

http://www.singletrackworld.com/article.php?sid=2001

RE:Disc mount location!
by: Cy on: Wednesday 31 May 2006 @ 11:26:34

It's on the front right for a couple of reasons. Firstly, it puts the
disc brake forces into the dropout, rather than out of it so you
won't get any axle movement with heavy disc braking. Secondly,
it means that regardless of what caliper you're using you can
always get to the mudguard eyes on the back of the dropouts.
There are just too many possible caliper configurations to say
'everything works with mudguards' so we put the mount properly
out of the way.

James Thomson

Date: 07 Nov 2007 05:23:12
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

Tony Raven wrote:
> In article <1194406213.024479.115730@i38g2000prf.googlegroups.com>,
> james.annan@gmail.com says...
>> <http://www.cotic.co.uk/geek/>
>>
>> I suppose the usual suspects will claim that this just proves that
>> Cotic do not know how to use QRs...
>>
>
> No, but they do know how to use Marketing 101. How do you differentiate
> yourself from the pack? Create a problem that only your product solves.
>
> Meanwhile how many years on are we now and what has actually happened
> during all that time? Even you haven't updated your website information
> for almost two years now.
>

why would he? you don't honestly expect him to admit that he only did
half the math or that wheel ejection just doesn't seem to happen* do you?

[* these two are related.]

Date: 07 Nov 2007 09:16:44
From: Dave Larrington
Subject: Re: Candid comments from Cotic on disks and QRs

In news:1194406213.024479.115730@i38g2000prf.googlegroups.com,
james.annan@gmail.com <james.annan@gmail.com > tweaked the Babbage-Engine to
tell us:
> I know their roadhog forks (with the disk mount on the front of the RH
> fork leg) have been commented on before, but their explanation for
> this design is refreshingly candid:

[snip]

Plus it makes life a lot easier when attaching mudguards :-)

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk >
Never play leapfrog with a unicorn.

Date: 07 Nov 2007 06:17:06
From: Michael Press
Subject: Re: Candid comments from Cotic on disks and QRs

In article
<1194406213.024479.115730@i38g2000prf.googlegroups.com >
,
"james.annan@gmail.com" <james.annan@gmail.com >
wrote:

> I know their roadhog forks (with the disk mount on the front of the RH
> fork leg) have been commented on before, but their explanation for
> this design is refreshingly candid:
>
> "Axle movement under disc braking is now a fairly well known
> phenomenon in mountain biking. Basically with the caliper positioned
> left rear (usual place), and a vertical dropout, there is a reaction
> of the braking force which tends to push the axle out of the dropout,
> hence you're relying on the friction of your QR to counteract this
> rather than a completely mechanical stop. Most manufacturers have
> moved to a slightly forward facing dropout to counteract this.
>
> "We've actually never experienced any trouble with this on our
> mountain bikes, but during prototype testing of the ROADHOG fork -
> which had the disc mount in the usual left rear position - we did
> actually experience some axle movement. Nothing actually came undone,
> but after some serious downhill braking on fast roads, the rotors
> would be rubbing a touch and the wheel would 'clunk' home in the
> dropout when we undid the axle nuts. This was clearly unacceptable, so
> we set about finding a solution."
>
> <http://www.cotic.co.uk/geek/>
>
> I suppose the usual suspects will claim that this just proves that
> Cotic do not know how to use QRs...

I never thought a manufacturer would have the sand
to obviate the problem by moving the calipers.
Good on them. Now their competitors will have
some explaining to do.

--
Michael Press

Date: 07 Nov 2007 09:27:33
From: Bill Sornson
Subject: Re: Candid comments from Cotic on disks and QRs

Michael Press wrote:
> I never thought a manufacturer would have the sand
> to obviate the problem by moving the calipers.

"Have the sand", Gracie? Never heard that one (and neither has a Quick
Google, apparently).

Curious Bill

Date: 07 Nov 2007 23:24:17
From: Michael Press
Subject: Re: Candid comments from Cotic on disks and QRs

In article <4731f591$0$28872$4c368faf@roadrunner.com >,
"Bill Sornson" <askme@ask.me > wrote:

> Michael Press wrote:
> > I never thought a manufacturer would have the sand
> > to obviate the problem by moving the calipers.
>
> "Have the sand", Gracie? Never heard that one (and neither has a Quick
> Google, apparently).

USA regional English. Means fortitude.

--
Michael Press

Date: 08 Nov 2007 22:17:51
From: Tom Sherman
Subject: Re: Candid comments from Cotic on disks and QRs

Michael Press wrote:
> In article <4731f591$0$28872$4c368faf@roadrunner.com>,
> "Bill Sornson" <askme@ask.me> wrote:
>
>> Michael Press wrote:
>>> I never thought a manufacturer would have the sand
>>> to obviate the problem by moving the calipers.
>> "Have the sand", Gracie? Never heard that one (and neither has a Quick
>> Google, apparently).
>
> USA regional English. Means fortitude.
>
I thought the meaning was obvious from the context.

--
Tom Sherman - Holstein-Friesland Bovinia
Tradition is the worst rational for action.

Date: 09 Nov 2007 04:50:58
From: Michael Press
Subject: Re: Candid comments from Cotic on disks and QRs

In article <fh0mtl$es9$1@registered.motzarella.org >,
Tom Sherman <sunsetss0003@REMOVETHISyahoo.com > wrote:

> Michael Press wrote:
> > In article <4731f591$0$28872$4c368faf@roadrunner.com>,
> > "Bill Sornson" <askme@ask.me> wrote:
> >
> >> Michael Press wrote:
> >>> I never thought a manufacturer would have the sand
> >>> to obviate the problem by moving the calipers.
> >> "Have the sand", Gracie? Never heard that one (and neither has a Quick
> >> Google, apparently).
> >
> > USA regional English. Means fortitude.
> >
> I thought the meaning was obvious from the context.

Several other similar terms were advanced
in this thread, but none of them comes close.

I cannot offer etymology or web site.
Read a hundred novels set in nineteenth
century rural and frontier America

--
Michael Press

Date: 08 Nov 2007 22:45:44
From: Bill Sornson
Subject: Re: Candid comments from Cotic on disks and QRs

Michael Press wrote:
> In article <fh0mtl$es9$1@registered.motzarella.org>,
> Tom Sherman <sunsetss0003@REMOVETHISyahoo.com> wrote:
>
>> Michael Press wrote:
>>> In article <4731f591$0$28872$4c368faf@roadrunner.com>,
>>> "Bill Sornson" <askme@ask.me> wrote:
>>>
>>>> Michael Press wrote:
>>>>> I never thought a manufacturer would have the sand
>>>>> to obviate the problem by moving the calipers.
>>>> "Have the sand", Gracie? Never heard that one (and neither has a
>>>> Quick Google, apparently).
>>>
>>> USA regional English. Means fortitude.
>>>
>> I thought the meaning was obvious from the context.
>
> Several other similar terms were advanced
> in this thread, but none of them comes close.
>
> I cannot offer etymology or web site.
> Read a hundred novels set in nineteenth
> century rural and frontier America

You gotta lotta sand demanding that!

Date: 07 Nov 2007 16:27:18
From: Bill Sornson
Subject: Re: Candid comments from Cotic on disks and QRs

Michael Press wrote:
> In article <4731f591$0$28872$4c368faf@roadrunner.com>,
> "Bill Sornson" <askme@ask.me> wrote:
>
>> Michael Press wrote:
>>> I never thought a manufacturer would have the sand
>>> to obviate the problem by moving the calipers.
>>
>> "Have the sand", Gracie? Never heard that one (and neither has a
>> Quick Google, apparently).
>
> USA regional English. Means fortitude.

http://www.google.com/search?q=%22have+the+sand%22&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8

Date: 08 Nov 2007 08:09:02
From: Tom
Subject: Re: Candid comments from Cotic on disks and QRs

Bill Sornson wrote:
> Michael Press wrote:
>> In article <4731f591$0$28872$4c368faf@roadrunner.com>,
>> "Bill Sornson" <askme@ask.me> wrote:
>>
>>> Michael Press wrote:
>>>> I never thought a manufacturer would have the sand
>>>> to obviate the problem by moving the calipers.
>>> "Have the sand", Gracie? Never heard that one (and neither has a
>>> Quick Google, apparently).
>> USA regional English. Means fortitude.
>
> http://www.google.com/search?q=%22have+the+sand%22&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8
>
>
New one on me, too.

http://www.google.com/search?hl=en&safe=off&rls=com.microsoft%3Aen-US&q=%22he%27s+got+the+sand%22&btnG=Search

"Got the stones" is one I am familiar with. Sand seems like very little
(or old and worn out) stones.

Cheers,

Tom

Date: 08 Nov 2007 16:30:59
From: Pete Biggs
Subject: Re: Candid comments from Cotic on disks and QRs

Tom wrote:

>>>>> I never thought a manufacturer would have the sand
>>>>> to obviate the problem by moving the calipers.
>>>> "Have the sand", Gracie? Never heard that one (and neither has a
>>>> Quick Google, apparently).
>>> USA regional English. Means fortitude.
>>
>> http://www.google.com/search?q=%22have+the+sand%22&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8
>>
>>
> New one on me, too.
>
> http://www.google.com/search?hl=en&safe=off&rls=com.microsoft%3Aen-US&q=%22he%27s+got+the+sand%22&btnG=Search
>
> "Got the stones" is one I am familiar with. Sand seems like very
> little (or old and worn out) stones.

I've never heard either.

It's "got the gumption" or "got the bottle", in British English slang.

~PB

Date: 08 Nov 2007 15:59:24
From: Tom
Subject: Re: Candid comments from Cotic on disks and QRs

Pete Biggs wrote:
> Tom wrote:
>
>>>>>> I never thought a manufacturer would have the sand
>>>>>> to obviate the problem by moving the calipers.
>>>>> "Have the sand", Gracie? Never heard that one (and neither has a
>>>>> Quick Google, apparently).
>>>> USA regional English. Means fortitude.
>>> http://www.google.com/search?q=%22have+the+sand%22&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8
>>>
>>>
>> New one on me, too.
>>
>> http://www.google.com/search?hl=en&safe=off&rls=com.microsoft%3Aen-US&q=%22he%27s+got+the+sand%22&btnG=Search
>>
>> "Got the stones" is one I am familiar with. Sand seems like very
>> little (or old and worn out) stones.
>
> I've never heard either.
>
> It's "got the gumption" or "got the bottle", in British English slang.
>
> ~PB
>
>
"Got the stones" is a polite euphemism for, um, well, you folks might
say "having bollocks".

We Merkuns have quite colorful slang, but I've never considered it to
hold a candle to British slang, particularly Cockney.They've really got
the cobbler's awls.

Cheers,

Tom

Date: 07 Nov 2007 05:40:28
From: james.annan@gmail.com
Subject: Re: Candid comments from Cotic on disks and QRs

On Nov 7, 1:52 pm, jim beam <spamvor...@bad.example.net > wrote:
> james.an...@gmail.com wrote:
>
> <snip crap>
>
> > I suppose the usual suspects will claim that this just proves that
> > Cotic do not know how to use QRs...
>
> have you done the math on retention force yet then james?

I suggest you direct your question towards Ty at Cotic, or perhaps his
skewers which refuse so stubbornly to submit to your superior "math"
skills.

James

Date: 07 Nov 2007 05:25:55
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

james.annan@gmail.com wrote:
> On Nov 7, 1:52 pm, jim beam <spamvor...@bad.example.net> wrote:
>> james.an...@gmail.com wrote:
>>
>> <snip crap>
>>
>>> I suppose the usual suspects will claim that this just proves that
>>> Cotic do not know how to use QRs...
>> have you done the math on retention force yet then james?
>
> I suggest you direct your question towards Ty at Cotic, or perhaps his
> skewers which refuse so stubbornly to submit to your superior "math"
> skills.
>
> James
>

in other words: "no."

man up and deal with it annan.

Date: 06 Nov 2007 20:52:31
From: jim beam
Subject: Re: Candid comments from Cotic on disks and QRs

james.annan@gmail.com wrote:
<snip crap >
> I suppose the usual suspects will claim that this just proves that
> Cotic do not know how to use QRs...

have you done the math on retention force yet then james?

Date: 07 Nov 2007 21:26:55
From: NickP
Subject: Re: Candid comments from Cotic on disks and QRs

"jim beam" <spamvortex@bad.example.net > wrote in message
news:89edncEZjLkS2azanZ2dnUVZ_o3inZ2d@speakeasy.net...
> james.annan@gmail.com wrote:
> <snip crap>
>> I suppose the usual suspects will claim that this just proves that
>> Cotic do not know how to use QRs...
>
> have you done the math on retention force yet then james?

Do something useful. Prove that the bee can't fly.

Date: 06 Nov 2007 21:40:12
From: A Muzi
Subject: Re: Candid comments from Cotic on disks and QRs

james.annan@gmail.com wrote:
> I know their roadhog forks (with the disk mount on the front of the RH
> fork leg) have been commented on before, but their explanation for
> this design is refreshingly candid:
>
> "Axle movement under disc braking is now a fairly well known
> phenomenon in mountain biking. Basically with the caliper positioned
> left rear (usual place), and a vertical dropout, there is a reaction
> of the braking force which tends to push the axle out of the dropout,
> hence you're relying on the friction of your QR to counteract this
> rather than a completely mechanical stop. Most manufacturers have
> moved to a slightly forward facing dropout to counteract this.
>
> "We've actually never experienced any trouble with this on our
> mountain bikes, but during prototype testing of the ROADHOG fork -
> which had the disc mount in the usual left rear position - we did
> actually experience some axle movement. Nothing actually came undone,
> but after some serious downhill braking on fast roads, the rotors
> would be rubbing a touch and the wheel would 'clunk' home in the
> dropout when we undid the axle nuts. This was clearly unacceptable, so
> we set about finding a solution."
>
> <http://www.cotic.co.uk/geek/>
>
> I suppose the usual suspects will claim that this just proves that
> Cotic do not know how to use QRs...

Could also be an external-aluminum-cam skewer. They are notorious for
inadequate clamping force. Lately tracked many noise complaints
'in drive train' to those skewers.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971