From: still_the_same_me@hotmail.com (James Annan)
Newsgroups: rec.bicycles.tech
Subject: More on disk brakes and quick release failure
Date: 20 Mar 2003 23:55:39 -0800
Message-ID: <c96ea403.0303202355.11241558@posting.google.com>

I've eventually got around to finishing off a web page I started back
in December following a crash I had when my disk brake pulled my front
wheel out of the fork. The aftermath of that crash was discussed here,
and there are pictures of it on
http://www.ne.jp/asahi/julesandjames/home/fork/

The new web pages is on:

http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/

and I'd appreciate any comment or criticism.

What prompted me to finish it off after a few months of
procrastination is hearing about yet another serious crash which seems
to have been due to the same basic problem: a disk brake puts a huge
force on the front wheel, in the direction of the open fork ends,
which may be far in excess of anything the QR is designed to handle.

James

From: jobst.brandt@stanfordalumni.org
Subject: Re: More on disk brakes and quick release failure
Newsgroups: rec.bicycles.tech
Message-ID: <E1sfa.479$JX2.47030@typhoon.sonic.net>
Date: Mon, 24 Mar 2003 00:10:12 GMT

James Annan writes:

> What prompted me to finish it off after a few months of
> procrastination is hearing about yet another serious crash which
> seems to have been due to the same basic problem: a disk brake puts
> a huge force on the front wheel, in the direction of the open fork
> ends, which may be far in excess of anything the QR is designed to
> handle.

To make this more direct, lets assume the bicycle is capable of
braking with 1g acceleration.  That means, for a low rider position,
the entire weight of rider and bicycle is bearing on the front
wheel... and that the rotational torque of the front wheel is its
radius times bicycle and rider weight.  The radius at which the brake
pads act is about a 6 inch while wheel periphery lies at about 13
inches.

That means the upward force on the brake pads is slightly greater than
twice (13/6) the horizontal force (which is equal to the vertical
force at 1g) on the front wheel.  Therefore, there is a net
disengagement force of half the rider-and-bicycle weight.  This is not
a safe condition when repeated often, especially on rough terrain
where this force is hammered onto the wheel retention.

This example is accurate because the ratio of forces is equally true
for lesser braking forces.  The example of 1g is to simplify
visualization by avoiding arithmetic.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: More on disk brakes and quick release failure
Newsgroups: rec.bicycles.tech
Message-ID: <lAvfa.506$JX2.54357@typhoon.sonic.net>
Date: Mon, 24 Mar 2003 04:12:01 GMT

Jose Rizal writes:

>> To make this more direct, lets assume the bicycle is capable of
>> braking with 1g acceleration.  That means, for a low rider
>> position, the entire weight of rider and bicycle is bearing on the
>> front wheel... and that the rotational torque of the front wheel is
>> its radius times bicycle and rider weight.  The radius at which the
>> brake pads act is about a 6 inch while wheel periphery lies at
>> about 13 inches.

>> That means the upward force on the brake pads is slightly greater
>> than twice (13/6) the horizontal force (which is equal to the
>> vertical force at 1g) on the front wheel.  Therefore, there is a
>> net disengagement force of half the rider-and-bicycle weight.  This
>> is not a safe condition when repeated often, especially on rough
>> terrain where this force is hammered onto the wheel retention.

> If you look at the geometry of the dropouts in front suspension
> forks (which arguably most disc brakes are used with), and the
> position of the disc brake caliper (regardless of model and rotor
> size, as the caliper locations are all behind and above the QR), the
> QR will tend to be pushed towards the rear half of the dropout
> rather than along the slot where the QR slides in and out at
> removal.

Only the vertical component of these forces that is important in wheel
retention.  Whether there is a rearward resultant is immaterial, the
axle not being retained by its friction against the vertical dropout
slot.  Whether the brake caliper is above or at the dropout does not
change the vertical component of its action which it perpendicular to
the radial line to the axle from the caliper centerline... essentially
horizontal.

> In other words, the retention of the QR axle in place when using
> disc brakes is not at all dependent on the tightness of the QR, but
> rather on the strength of the dropout.  The safety of this
> arrangement is not as questionable as you imply.

It is exactly as I and others have stated.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

Message-ID: <3E7ED71E.1070706@hotmail.com>
Date: Mon, 24 Mar 2003 18:59:58 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech
Subject: Re: More on disk brakes and quick release failure

jobst.brandt@stanfordalumni.org wrote:

>
> To make this more direct, lets assume the bicycle is capable of
> braking with 1g acceleration.  That means, for a low rider position,
> the entire weight of rider and bicycle is bearing on the front
> wheel... and that the rotational torque of the front wheel is its
> radius times bicycle and rider weight.  The radius at which the brake
> pads act is about a 6 inch while wheel periphery lies at about 13
> inches.
>
> That means the upward force on the brake pads is slightly greater than
> twice (13/6) the horizontal force (which is equal to the vertical
> force at 1g) on the front wheel.  Therefore, there is a net
> disengagement force of half the rider-and-bicycle weight.  This is not
> a safe condition when repeated often, especially on rough terrain
> where this force is hammered onto the wheel retention.
>
> This example is accurate because the ratio of forces is equally true
> for lesser braking forces.  The example of 1g is to simplify
> visualization by avoiding arithmetic.

I think it's a bit worse than you calculated, since you have used wheel
radius but disk diameter in the calculation. Even my largeish disks are
only 185mm diameter, 3.6" to the outer edge and a bit less than that at
the centre of the pad. Also, the braking force acts primarily on one
dropout whereas the body weight is shared across two. Nevertheless, the
point is clear enough.

James

From: jobst.brandt@stanfordalumni.org
Subject: Re: More on disk brakes and quick release failure
Newsgroups: rec.bicycles.tech
Message-ID: <wkxga.1116$JX2.97172@typhoon.sonic.net>
Date: Thu, 27 Mar 2003 07:00:44 GMT

Chris Bird writes:

>> Why are you using a Hope M4 on the front wheel of a tandem?  That's
>> an 8" downhill brake designed for downhill forks with 20mm axles,
>> not ridged QR forks.

> To be fair, the rotor is 185mm (7.3"), which is in the middle of the
> range of the more common sizes (165, 185, 205mm).  It's true that
> consumers are advised by most, if not all disc brake manufacturers,
> not to use the larger disc rotors with standard QR dropouts.  Many
> people (especially teenagers) do it anyway and there are certainly
> reports of the axle pulling out of the dropout where they didn't
> with the smaller rotors - and this is on modern suspension forks
> with lawyer lips.

The smaller the disk diameter, the greater the disengagement force for
the same braking effect.  Therefore, I see no connection between
larger disks and more wheel disengagements.  What is less apparent,
is that a disk brake puts the same bending force that appears at the
fork crown on the end of the single fork blade at the caliper.

This severe bending moment is the reason not to put a disk brake on a
conventional bicycle (road) fork with a slender blade end, an end that
is not intended to carry bending loads like those at the large
diameter end at the fork crown.

> Of course, some of these people might not be tightening their QR
> skewers tightly enough but surely some of them are and this would
> suggest that there is not a huge safety margin.  Of course these
> anecdotes are not worth very much but perhaps it is worth looking at
> simply as a way of approaching the issue differently.

I find amazing how, by insinuation, this whole matter is being
relegated to operator error.  Nearly all of these replies seem like
so much whistling in the dark, for fear that someone will recognize
that disks are inappropriate for front wheels as used today.  Face it,
this is not a reasonable design.

> A 20mm _through-axle_ fork would have been a safe bet with an 8"
> disc for sure.  However, a lot of the 20mm suspension forks don't
> use a through-axle but rather a similar (but larger) QR setup - in
> fact, the axle I use with my Marzocchi QR20 uses a skewer of the
> _same diameter and pitch_ as a regular QR skewer nested inside the
> 20mm axle - no advantage is taken to increase the clamping force.
> Of course there is greater retention anyway by virtue of the
> proportionally larger axle, dropout and "lawyer lips" but for
> 2001(?), Marzocchi chose to add separate retention tabs which
> spanned across the bottom of the dropouts and were bolted down
> separately ("QR20+") though I understand that this is no longer the
> case, probably because people found it very inconvenient.  I'm not
> aware of people having problems with the original QR20 system with
> 8" discs but there must have been some reason for them to have
> played around with the design.

So what is a larger skewer or axle supposed to do?  The implication is
that there are forces here that are not present with rim brakes.  So!
What are these forces if they aren't disengagement forces.  Obviously
it is not an axle or bearing overload, because these are not failing.
What is failing is the attachment of the wheel to the dropout.  I
think we've gone through the simple force analysis to show that there
is a large downward (wheel separating) force on the axle.

>> Also, ridge forks are designed to have some flex in them to provide
>> a small amount of suspension, while suspension forks are very
>> stiff.

> I'm not sure that this is a rigid vs suspension issue so much as an
> issue of whether the fork was designed to deal with the loads of rim
> brakes or disc brakes or both.

I don't know where the flex in "rigid" forks is supposed to come from.
If you mean conventional tapered fork blades as on road bicycles, then
that is an additional hazard that will cause fork failure at the
caliper attachment.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: More on disk brakes and quick release failure
Newsgroups: rec.bicycles.tech
Message-ID: <mpxga.1117$JX2.97200@typhoon.sonic.net>
Date: Thu, 27 Mar 2003 07:05:54 GMT

Karl Frisch writes:

> Avid does warn against using their 203's with a standard quick
> release.  If you look at their fork compatibility chart it says "Be
> aware that fork manufactures discourage the use of anything larger
> than a 185mm rotor on a standard quick-release." Nice to see that
> they put the onus on the fork manufacturer.

What reason is given for the warning?  It seems like another
misunderstanding of the bicycle industry.  The larger the disk, the
lower the forces.  In fact when the contact diameter of the disk pads
reach that of the rim (as in rim brakes) braking forces are minimized.
What is going on here?

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: More on disk brakes and quick release failure
Newsgroups: rec.bicycles.tech
Message-ID: <syMga.1393$JX2.109147@typhoon.sonic.net>
Date: Fri, 28 Mar 2003 00:19:36 GMT

Tim McNamara writes:

>> I find amazing how, by insinuation, this whole matter is being
>> relegated to operator error.

> As you have pointed out in many posts, it is very frequent for what
> is in fact operator error to be misconstrued as faulty design,
> especially in lawsuits.  You've testified in court about that very
> topic on multiple occasions, from what you've written over the years.
> I recall that you've said that in almost every case of blaming the
> design- especially as related to quick releases- the cause was in
> fact operator error.

This never involved disk brakes, it was always with reference to
bicycles with rim brakes and conventional QR's.  These do not loosen
from use as John Howard claimed in his expert testimony that brought
"lawyer lips" to bicycling.  I sense that you are pressing the
operator error scenario in spite of irrefutable analysis of large
disengagement forces caused by disk brakes.

> So, given that, I think it was a reasonable first question to ask:  is
> the problem reported by the OP caused by operator error rather than
> poor design?  If it is from poor design, why are we not flooded with
> similar reports by experienced cyclists who know how to use a quick
> release?

That is because most riders over tighten QR's anyway as we see from
frequent bearing failures, a subject discussed under another thread.
As it is, riders err on the safe side but when a failure occurs, it is
most likely mis-attributed to skewer failure that occurs if there is
brake induced wheel separation.

> This is quite unlike SUV rollovers occurring in normal traffic
> maneuvers, where it is abundantly clear that the design of the
> vehicles is faulty simply from the frequency of occurrence under
> normal conditions.

The SUV rollover occurs because people believe they are driving a
vehicle as safe and fool proof as a sedan that will not turn over on a
dry pavement spin-out.  SUV's and similar vehicles were formerly
driven mainly by people aware of their lateral acceleration
limitations.  Our newspapers are reporting SUV rollovers more
frequently these days, ones that occurred as a result of a spin-out,
an otherwise benign incident.  The latest involved a fatality of a
noted athlete who was a passenger.

>> Nearly all of these replies seem like so much whistling in the
>> dark, for fear that someone will recognize that disks are
>> inappropriate for front wheels as used today.  Face it, this is not
>> a reasonable design.

> If we are not seeing many such failures, is the design still
> necessarily a bad one?

Yes, especially because one can demonstrate that it causes wheel
separation if the QR is not unduly tight.  Another reason could be
that these incidents usually occur when a rider is performing a
difficult descending maneuver that people generally consider risky.
That would suppress many complaints, especially if the rider was
unaware why the wheel came out.

> Or does a standard Campagnolo or Shimano type QR have adequate
> clamping force to keep the wheel in the dropouts, if properly used?

With knurled jam nuts, sufficient retention is possible but I would
not like to place my safety on that condition.  It's like asking
someone to hang a bicycle from the front wheel and then hang his
entire weight on the bicycle by swinging from the rear wheel... over a
substantial drop off.  If I had my feet near the ground, OK but not if
I was to risk my well being on it.

> I can't answer either of those questions, not having the technical
> knowledge.  I can predict that this would be the industry stance,
> however, because it's cheaper to blame the operator than to recall
> 100,000 or more forks and brake calipers and replace them with a
> corrected design.

I don't see why "we" should be apologists for the industry and offer
other explanations for the reported failures.  It is more our place to
analyze the effect, suggest solutions, and to be fully aware of the
hazard.

> It appears from the available information and explanations that the
> current crop of front disc brakes for bicycles has a significant
> flaw, in that the front wheel braking force attempts to force the
> axle out of the dropout slot.  The harder you brake, the greater the
> force pushing the axle out without much increase in load on the
> wheel to counteract the ejection of the axle.  As I mentioned
> earlier, a side view photograph and a basic comprehension of action
> and reaction are enough to explain the problem succinctly without
> resorting to mathematics.  The obvious cure is to design the system
> to put the caliper in front of the fork; current forks and calipers
> should be recalled and replaced.

That sounds reasonable to me but the problem remains that the bicycle
industry should be more technically astute and discover these things
before they get on the market.

> This should be brought to the attention of fork and brake
> manufacturers for immediate correction, and should probably also be
> brought to the attention of the CPSC to enforce a recall.  A Usenet
> newsgroup with a few hundred relatively sophisticated readers-
> compared to the tens of thousands of people who have purchased such
> bicycles- is not going to resolve the problem.

I am amazed that bicycle companies do not lurk on wreck.bike just to
see what ails the users and what they discover.  This is by and large
typical of the bicycle business.  The few people from the business who
participate here are not in much of a position to change manufacturing
trends.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Missy Giove's QR pops open (long)
Newsgroups: rec.bicycles.tech,alt.mountain-bike
Message-ID: <5DQza.16660$JX2.1027710@typhoon.sonic.net>
Date: Sat, 24 May 2003 20:29:53 GMT

James Annan writes:

> You've made it clear that you do not consider that the evidence
> presented is adequate to logically disprove your hypothesis that all
> failures are due to operator error. So I won't try to change your
> mind directly, but it seems to me that your own position is rather
> implausible.

> Do you actually deny that the QR can unscrew in the manner
> described, or do you claim that this unscrewing is only possible
> when the QR is incorrectly used in some way? Many people have
> reported loosening, often on a regular basis, and those who install
> the lever on the LH can see its change in position. One even saw it
> moving as he was riding along! I will assume therefore that you
> prefer the second possibility, ie any unscrewing is due to the user
> incorrectly installing the QR.

I think there is another effect at work that may have a greater effect
than it might at first seem.  Only the left fork blade is subjected to
brake torque so its extremity bends rearward over its entire length
while the other blade sees only a bending load and articulates in a
small fraction of the angle its partner does.  This differential fork
end rotation about the wheel axle has unscrewing motion that may
exceed the sliding motion or at least add to its effects.

This consideration comes from the evaluation of putting a hub brake on
a conventional road fork that is usually light and slender at its end.
Such forks will break from fatigue if not from overload because the
fork end will be subjected to torque for which it is not designed.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Missy Giove's QR pops open (long)
Newsgroups: rec.bicycles.tech,alt.mountain-bike
Message-ID: <T4Wza.16728$JX2.1034325@typhoon.sonic.net>
Date: Sun, 25 May 2003 02:42:59 GMT

James Annan writes:

>> I think there is another effect at work that may have a greater
>> effect than it might at first seem.  Only the left fork blade is
>> subjected to brake torque so its extremity bends rearward over its
>> entire length while the other blade sees only a bending load and
>> articulates in a small fraction of the angle its partner does.
>> This differential fork end rotation about the wheel axle has
>> unscrewing motion that may exceed the sliding motion or at least
>> add to its effects.

>> This consideration comes from the evaluation of putting a hub brake
>> on a conventional road fork that is usually light and slender at
>> its end.  Such forks will break from fatigue if not from overload
>> because the fork end will be subjected to torque for which it is
>> not designed.

> It's certainly something to consider and I am well aware of the risk
> of missing some aspect that turns out to be important.  After all, I
> spent some time trying to demonstrate that the QR could be pushed
> over the lip even while remaining tight!  Also, as I mentioned to
> Tony Raven, I am not confident that changing the slot angle itself
> will be a perfect solution, although it must surely reduce the
> likelihood of ejecting the wheel suddenly.

The angle is not the solution because load reversal and torque are the
effects loosens the QR and caliper position generates wheel disengaging
forces.  Therefore, the caliper must be moved ahead of the fork.

> The torque definitely seems to be a big issue for road forks with
> 1/2" diameter thin-walled tips, but a typical suspension fork is
> about 3 times this diameter and presumably much thicker-walled too.

Suspension forks have sliding bushings that have clearance and are not
located at the ends of the stanchions.  This has inherent slop that
allows fork end rotation.  To avoid this one sided load, motorcycles
use a disc on both sides of the front wheel, not because they need the
extra brake area, but because the need to balance the load.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Missy Giove's QR pops open (long)
Newsgroups: rec.bicycles.tech,alt.mountain-bike
Message-ID: <k%Xza.16746$JX2.1035151@typhoon.sonic.net>
Date: Sun, 25 May 2003 04:53:36 GMT

Ryan Cousineau writes:

>> The angle is not the solution because load reversal and torque are
>> the effects loosens the QR and caliper position generates wheel
>> disengaging forces.  Therefore, the caliper must be moved ahead of
>> the fork.

>> > The torque definitely seems to be a big issue for road forks with
>> > 1/2" diameter thin-walled tips, but a typical suspension fork is
>> > about 3 times this diameter and presumably much thicker-walled
>> > too.

>> Suspension forks have sliding bushings that have clearance and are
>> not located at the ends of the stanchions.  This has inherent slop
>> that allows fork end rotation.  To avoid this one sided load,
>> motorcycles use a disc on both sides of the front wheel, not
>> because they need the extra brake area, but because the need to
>> balance the load.

> Hm. An awful lot of motorcycle makers have got this one wrong, then.

> There are many, many road motorcycles that use single discs. There
> is even one company (Buell) that has produced what might be called a
> "rim-disc" or some such:

> http://tinyurl.com/cloa

> As you can see from the picture, the motorcycle has a single disc
> that runs near the rim of the front wheel. Very large surface area,
> though I don't know how it compares to twin front disc bikes.

So that's a lot like a rim brake that produces no significant fork tip
torque.  You must wonder why they do this.  As I said, others use dual
disks and avoid any unwanted steering effect, Buell (Harley Davidson)
makes a rim brake.  Meanwhile, you'll find that most high performance
motos use dual discs.

> Besides the interesting Buell concept, almost all motorcycle makers
> have low-end road models (not to mention cruisers and other bikes)
> with single discs.

I'm not surprised.  However, the motorcycle engineers are not funded
to the degree that auto racing is and don't develop engines and
suspensions that require extreme innovation and skill, along with a
rigorous test laboratory in the field.  There are still a bunch of
archaic designs being used that have no merit and are not used
anywhere else in the racing business similar to the tubular tire fad
in bicycles... we've always done it that way.

> Virtually no dirt bikes (unless you count absurdities like the
> R1100GS as a dirt bike) use dual front discs.

> Of course, they also use through axles,

And they are not affected as much by small steering errors as a road
motorcycle at high speed is.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: More on disk brakes and wheel ejection
Newsgroups: rec.bicycles.tech
Message-ID: <33yWa.7447$dk4.327551@typhoon.sonic.net>
Date: Fri, 01 Aug 2003 18:11:11 GMT

Sheldon Brown writes:

>> We don't need no steenkin further research, as they say.  All that
>> is needed is to move the caliper ahead of the fork, nothing more.
>> In my estimation, this is the only reasonable solution that would
>> conclusively solve the problem.

> That would require re-designing the calipers, n'es-ce pas?

> What about changing the angle of the wheel slot in the fork ends to
> make it perpendicular to the braking reaction force?  This would
> seem a lot easier to do.

I think we went through all that.  As long as the braking forces are
down and the wheel loads are up, the axle will move and the QR will
unscrew.  Therefore, changing the dropout slot orientation is only a
bandaid and does not attack the underlying problem.  The caliper must
be in front so that its reaction forces are in the same direction as
the wheel load forces.  Only then will the reliable retention of the
wheel be assured.

> Forgive me if this has already been suggested and dismissed for some
> good reason--I haven't been reading all of the posts in this
> looooong thread.

Well, it hasn't been put this way before but it has been part of the
argument for caliper placement.  I'm glad you brought it up again so
that that aspect does not get lost.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

Message-ID: <3F2AE9ED.6000908@hotmail.com>
Date: Sat, 02 Aug 2003 07:30:05 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech
Subject: Re: More on disk brakes and wheel ejection

John Rees wrote:
> <jobst.brandt@stanfordalumni.org> wrote in message
> news:5lpWa.7311$dk4.324995@typhoon.sonic.net...

>>
>>We don't need no steenkin further research, as they say.  All that is
>>needed is to move the caliper ahead of the fork, nothing more.  In my
>>estimation, this is the only reasonable solution that would
>>conclusively solve the problem.
>>
>>I cannot understand what all the hand wringing is about.  Just do it!
>>This is fretting at its worst.
>
>
> Whether or not the calliper is moved on the forks there's a lot of expensive
> bikes out there that will not or cannot get retrofitted.

I'm sure you've mostly worked this out, but the reason why the
manufacturers appear to be acting like paralysed bunnies in headlights
is that once their liability is established, they will be faced with a
massive recall problem and an indeterminate backlog of compensation claims.

Of course, by doing nothing, they increase the number of victims (and
the number of forks in circulation that will need to be altered). On top
of this, they also risk not only merely paying compensation but
unlimited punitive damages on top of that for continuing to sell these
products with such an obvious flaw. But hey, what does that matter when
there are peak summer sales figures to enjoy? It is hard for them to
keep up the pretence that they cannot create or understand the problem
when an interested (but originally sceptical) bike shop owner can
reproduce the phenomenon so easily and reliably just by riding to work a
handful of times.

Some of you will have noticed that the CPSC issued a recall notice for
some forks just this week. This was some high-end carbon model with a
theoretical cracking problem that has not resulted in any incidents let
alone injuries!

Meanwhile, back in the real world, there is a steady trickle of stories
concerning serious injury as riders misplace their front wheels on fast
descents (all with disk brakes, of course). Several more people have
spent time in hospital in the last few weeks, including a couple of
people who had several days there due to serious head injuries.

James

From: jobst.brandt@stanfordalumni.org
Subject: Re: More on disk brakes and wheel ejection
Newsgroups: rec.bicycles.tech
Message-ID: <5m1Za.9877$dk4.403087@typhoon.sonic.net>
Date: Sat, 09 Aug 2003 07:25:53 GMT

James Annan writes:

>> <jobst.brandt@stanfordalumni.org> wrote in message
>> news:5lpWa.7311$dk4.324995@typhoon.sonic.net...


>>> We don't need no steenkin further research, as they say.  All that
>>> is needed is to move the caliper ahead of the fork, nothing more.
>>> In my estimation, this is the only reasonable solution that would
>>> conclusively solve the problem.

>>> I cannot understand what all the hand wringing is about.  Just do
>>> it!  This is fretting at its worst.

>> Whether or not the caliper is moved on the forks there's a lot of
>> expensive bikes out there that will not or cannot get retrofitted.

> I'm sure you've mostly worked this out, but the reason why the
> manufacturers appear to be acting like paralyzed bunnies in
> headlights is that once their liability is established, they will be
> faced with a massive recall problem and an indeterminate backlog of
> compensation claims.

I don't think it is as bad as you describe.  If manufacturers acted
now, modified their forks and recalled existing models, a solid
defense would be that the current design was general practice for all
bicycles and that no one found fault with it until a large user field
had established with a large variety of rider demands and operator
skills.  This would demonstrate a good faith response to a belated
discovery that should be without major criticism.  This would be
different, had there been some manufacturers who placed calipers ahead
of the fork and to whom one could point as proof of a known hazard.

What is done as retrofit is up to the industry.  I see making a fail
safe "bandaid" that may not be graceful or stylish, but it could be
made safe at the expense of clean elegance.  I even envisage a
retention means that would prevent the wheel from ejecting but without
trying to prevent loosening, so that essentially a "buzzer" noticeable
(looseness) would alert the rider to tighten the QR.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: More on disk brakes and wheel ejection
Newsgroups: rec.bicycles.tech
Message-ID: <nIiZa.10100$dk4.411123@typhoon.sonic.net>
Date: Sun, 10 Aug 2003 03:10:11 GMT

Rick Onanian writes:

> I agree that changing the position of the caliper and/or changing
> the design of the existing open dropout system would eliminate the
> safety need for a skewer that won't unscrew.

This is a recurring theme that misses the point as I see it.  A hand
installed wheel, one without a wrench tightened conical "lug nut" as
on automobile wheels, WILL move, either because it is not tight enough
to restrain all movement, or because it was inadvertently not
tightened sufficiently.  As long as the disengaging force on the axle
remains, the problem remains with any manually tightened QR mechanism
that I can visualize.  In this respect, I find suggestions for a
modified QR or dropout are wishful thinking.

As I said, moving the caliper ahead of the fork is an absolutely
effective solution while any modification of the dropout without it
can only appeal to riders who do not believe that the current
configuration is dangerous or that it is operator error of not
tightening the wheel sufficiently.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

Date: Fri, 19 Mar 2004 21:47:23 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: "Actually you are the first person to bring up this issue"
Message-ID: <405aed81$0$23537$44c9b20d@news3.asahi-net.or.jp>

It's now a year since the QR/disk brake problem hit the headlines, and I
thought some of you might be interested in hearing how the manufacturers
are dealing with it.

A few weeks ago, yet another rider who had just upgraded to disk brakes
found that he couldn't reliably keep his wheel stationary in the
dropouts under heavy braking. So far, so normal. Having found my web
page, he then did what it seems no mountain biker before him has
bothered to do, and asked the manufacturers for advice. In all, he spoke
to Answer (Manitou), Fox Racing, and also Avid and Chris King.

The clever ones will already have worked out where the subject line came
from. Yes, to a man (actually, 3 men and one woman), they all insisted
that he was the first person to have ever brought this up with them, and
no, they had no plans to do anything about it, because no-one else ever
had this problem. One of them (Avid) did say that it was obviously
dangerous and he should not ride the bike in that state, but had no
useful suggestion as to what he could do to make it safe.

So there you have it. At this rate, by the time next year's complaint
comes in, they will presumably have forgotten this first one. How
convenient for them. Those who thought that it wouldn't do to kick up a
fuss because the poor manufacturers were doing their best, may wish to
re-examine their approach. Or else studiously ignore this post in the
vain hope that the problem will go away.

James

From: still_the_same_me@hotmail.com (James Annan)
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Date: 19 Mar 2004 15:07:17 -0800
Message-ID: <c96ea403.0403191507.5ffcaedb@posting.google.com>

"Pete Biggs" <pclemantine{remove_fruit}@biggs.tc> wrote in message news:<c3f7us$1suf32$1@ID-144931.news.uni-berlin.de>...
> Jon Senior wrote:
>
> >> Is there such a thing as too tight? Is there a danger of the skewer
> >> being over-stressed and being more likely to fail?
> >
> > With quick-release, if you have the skewers too tight, they can make
> > the hub bearings bind. Giant's bike manual suggested that the levers
> > were too loose if closing them didn't leave an imprint in my palm.
> > Doing so meant the wheels stopped rotating within about 3/4
> > revolution, compared to around 20 when loose.
>
> Cones can be loosened to compensate for a tighter skewer.  In other words,
> readjust so there's more play in the hub before QR is done up, to cope
> with the greater axle compression when it is closed.
>     I don't think it's an issue for cartridge bearings.

Chris King specifically warn against overtightening the skewer,
because compressing the (presumably cartridge) bearing will accelerate
wear and result in a wheel which is chronically wobbbly.

I don't know how tight a skewer would have to be to make it
significantly more likely to fail in itself, but I would imagine there
must be some tendency in that direction. Anyone who really cares could
always try asking the manufacturers themselves...but from what I've
seen, those who supply recommendations (eg lever torque) tend to give
both a lower and an upper limit.

James

From: still_the_same_me@hotmail.com (James Annan)
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Date: 19 Mar 2004 15:57:54 -0800
Message-ID: <c96ea403.0403191557.5554d8f3@posting.google.com>

"Frobnitz" <news_postings@blueyonder.co.uk> wrote in message news:<c3f4o1$f6q$1@scotsman.ed.ac.uk>...

> Have you contacted someone like Watchdog (UK consumer affairs program, for
> the non-UK readers on the x-post) to see if they are interested.

No, I don't think there is any point in that. Firstly, it doesn't
affect me directly, and secondly, they are hardly going to take a
complaint seriously that has only ever been noticed by one rider (and
he didn't even have a crash or anything, it's just that his wheel
won't stay put). Since it's already been cleared by the CPSC, there is
obviously no design problem and I guess I must have made the whole
thing up. It was quite a hassle making all the fake user accounts on
singletrackworld:

http://www.singletrackworld.com/forum/read.php?f=2&i=934406&t=933851

and just to make it seem more authentic I forged this review and
hacked into Marin's site:

http://www.marin.co.uk/marin-2004/reviews.php?ID=47

James

Date: Sat, 20 Mar 2004 14:44:14 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <405bdbdb$0$23536$44c9b20d@news3.asahi-net.or.jp>

tcmedara wrote:

> LOL. While I think you are an obsessed quasi-religious zealot, that's not
> why I'm going to goof on you.....
>
>  Dumabass, Frobnitz was *supporting you* !

Yeah, I realised that. I guess humo(u)r doesn't travel well.

> He was suggesting that rather
> than spam up a bunch of newsgroups where people are probably smart enough to
> tighten their QR, you should direct your efforts at the appropriate
> regulatory agencies and actually try to do something to fix the "problem".

Actually, although you probably mean well, both you and Frobnitz don't
seem to realise that I _did_ contact the "appropriate regulatory
authorities" last year. They (or, to be precise, the CPSC) said they
needed specific complaints of individual problems, rather than a general
warning of a theoretical design problem.

Of course, when I suggested that some of those riders who had described
their incidents might care to contact the CPSC, I was roundly criticised
for "scaremongering", and as far as I know, not a single rider bothered.
Many of those who understood the problem or had even seen it for
themselves had the touchingly naive belief that the manufacturers would
fix the problem all on their own and it would be overkill to actually
pressure them into doing so. Of course, what they didn't realise is that
the manufacturers have a strong financial incentive to keep the current
designs, since when Joe Bloggs upgrades to disks and finds his QR fork
is not up to the job, he then generally goes out and buys a bolt-through
fork. It's easy enough to see who wins out of this.

Roll on one year, and entirely predictably, the manufacturers are still
pretending the problem doesn't exist. They must be laughing all the way
to the bank.

As for J DeMarco at the CPSC, well he commissioned Mark LaPlant of
Cannondale to report on the issue, and surprisingly enough the turkey
didn't vote for Christmas. In fact he produced a bullshit whitewash
which he refuses to publish. But since all the manufacturers can
(apparently truthfully) claim that no rider has ever reported any
incident, there really is little more that the CPSC can (or probably
should) do.

> Your rejection of that course of action suggests that you're more interested
> in pursuing your own personal crusade rather than actually solving a
> problem -- percieved or otherwise.
>
> Rather than thank him for the suggestion or offer a counterpoint to why it's
> not a viable option,

I hope you will now agree that I have offered a counterpoint as to why
it is not a viable option, and I'm sorry for not giving sufficient
explanation earlier. The simple fact is that while MTBers refuse to do
more than grumble on bulletin boards, there is no real complaint to
raise with anyone. I realised several months ago that there was really
nothing more for me to do, but people still keep on emailing me with
their stories, and I thought this latest one was sufficiently
interesting to be worth sharing. Maybe next year there will be another.
Don't hold your breath.

James

From: jobst.brandt@stanfordalumni.org
Subject: Re: "Actually you are the first person to bring up this issue"
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Message-ID: <bs07c.883$Fo4.8423@typhoon.sonic.net>
Date: Sat, 20 Mar 2004 18:55:03 GMT

anonymous snipes:

> The bottom line here is not whether or not this issue is truthful,
> but how and why it happens.  I for one would like to know what the
> circumstances are in each case that may trigger it.

> So the question is this: in each case where the problem occured,
> what were the conditions? was it human error, or part failure?

How about doing a test that takes about 30 seconds.  Open the QR on a
disc brake equipped front wheel.  Push the bicycle forward and notice
what the axle does.

Just so it is clear what occurs.  The fork dropout rises from the axle
and is retained only by the retention lips. the motion involved will
cause a properly closed QR to loosen on repeated hard braking because
there is ever so little motion with each brake application.  If the QR
is extremely tight, it can prevent this over a longer time but in the
long run, if the wheel is not removed for one reason or another and
reinstalled again made extra tight, it will loosen.

The point is that the wheel should not have disengaging forces while
braking.  These would not occur if the caliper were mounted in front
of the fork.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: "Actually you are the first person to bring up this issue"
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Message-ID: <SZ07c.890$Fo4.8581@typhoon.sonic.net>
Date: Sat, 20 Mar 2004 19:30:58 GMT

Tim McNamara writes:

>> I keep hearing about this issue with greater frequency, but I've
>> been running discs for a few years now and it's only popped out
>> once in that time. It was my fault on that occasion, I realized
>> afterwards that I hadn't properly tightend the QR.

What means "properly tightened"?

> See, that's the point.  The brake should be designed so that it
> *can't* force the wheel out of the dropouts, even if the QR is left
> completely loose.  It's a design flaw, an epic design flaw that will
> cost some manufacturer a *lot* of money in court some day.  No other
> current brake design that I'm aware of puts an ejection force into
> the wheel in normal operation, but front disk brakes do.

Hold it!  Even though this has been discussed at great length here in
wreck.bike, it appears to me that most of the respondents did not
understand that a disc caliper behind the fork causes a wheel
disengaging force, and that repeated braking WILL loosen a QR.
Therefore, with the majority of contributors resting in the "James
Annan is all wrong" boat what you just posted gets us back to the
start, a few hundred responses ago.

Brake forces and their reactions are apparently too complex to be
discussed among bicyclists who believe anything bought in a bicycle
shop is safely designed.

http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/

Jobst Brandt
jobst.brandt@stanfordalumni.org

Date: Sun, 21 Mar 2004 07:04:54 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <405cc1bd$0$23533$44c9b20d@news3.asahi-net.or.jp>

tcmedara wrote:


> I don't mean well at all.  I responded 'cause I find humor in pointing out
> logical inconsistency.  I didn't "realise" you'd contact anyone because you
> rejected the notion as not worthwhile.  I'm pretty intelligent, but not
> clairvoyent.  I could have realized it had you bothered to mention it.

If you had glanced at the website you would have seen. In fact, anyone
coming new to the debate who thinks they have some startling insight
should probably read it. My dealings with the CPSC are detailed at

http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/cpsc.html

and you might learn something from the related pages too.

>>As for J DeMarco at the CPSC, well he commissioned Mark LaPlant of
>>Cannondale to report on the issue, and surprisingly enough the turkey
>>didn't vote for Christmas. In fact he produced a bullshit whitewash
>>which he refuses to publish. But since all the manufacturers can
>>(apparently truthfully) claim that no rider has ever reported any
>>incident, there really is little more that the CPSC can (or probably
>>should) do.
>
>
> Again, not the "truth" you espouse so therefore it's a "whitewash".  Next
> you're going to tell us the CIA is behind it all right?  Ya know, if you
> could document actual circumstances (rather than internet anecdotes and
> gossip), than you could prove the point to the apparently intransigent CPSC.

I suggest you read the letters I've posted on that page, and try to work
out a plausible explanation for his behaviour.

A quick summary:

I emailed DeMarco several times in August and September, and was
repeatedly told that a letter was on its way, or had even been sent.
Eventually I got a bland Word document as an email attachment.

In mid October, I received the official letter which was significantly
different. Although dated 2 Sept, it was only posted on the 15th
October, a couple of days _after_ the ASTM meeting to which it refers.

DeMarco has not replied to any of my emails since that date. Mark
Laplant refuses to publish his report which was presented at the "open"
ASTM meeting.

Ask them yourselves if you don't believe me. Oh, I forgot, you're one of
those who prefer to piss and moan on usenet than actually _do_ anything.

James

Date: Sun, 21 Mar 2004 17:34:34 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <405d5554$0$23536$44c9b20d@news3.asahi-net.or.jp>

tcmedara wrote:

> My point was that the CPSC would issue recalls for bicycle components, even
> based on minor or even potential injury.  I'm merely asking the question of
> why, in light of the propensity for the CPSC to protect us from relatively
> minor risks, would they dismiss the disk/qr issue so readily?

Because the manufacturers have insisted that it has never happened to
any users, and given an absence of riders prepared to contact them to
say otherwise (even though they are happy to write about it on usenet
and bulletin boards) there is no reason for the CPSC to doubt that. In
their eyes, it remains a hypothetical problem which never happens in
real life. Were it not for all the people who have described their
symptoms of loosening QRs - and several who have lost the front wheel in
situations where operator error is an implausible explanation - they
could even be right. But I didn't just sit down with a pencil and pad of
paper one day and invent this whole thing up out of my imagination, the
conclusions were drawn from an analysis of dozens of consistent and
convincing descriptions of the same phenomona. It is not a coincidence
that the explanation finally came to me about a fortnight after the news
of Russ' crash.

James

From: jobst.brandt@stanfordalumni.org
Subject: Re: "Actually you are the first person to bring up this issue"
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Message-ID: <I4J7c.1234$Fo4.13250@typhoon.sonic.net>
Date: Mon, 22 Mar 2004 21:42:00 GMT

Mark Hickey writes:

> I'm intrigued by your assertion that the QR is very likely to loosen
> - you seem to be saying it's almost inevitable (though presumably
> the period required is likely much longer than the time between
> "normal" wheel removals).

> The one stumbling point I have in accepting the premise is due to
> the physical evidence / actions of a wheel while it's loosening.

> IF the QR begins to loosen, presumably it won't happen all at once.
> Therefore, for some period of time, the QR will be rotating against
> the dropout face while still quite tight, and the "teeth" will
> surely leave evidence of the rotation on the soft aluminum or
> magnesium dropout face.

> Also, the front wheel will become VERY noticeably loose prior to the
> point the QR can be ejected over the lawyer lips - this will be
> accompanied by all sorts of brake rub and other nasty behavior by
> the front wheel I'd suspect.  Perhaps during a gonzo downhill run
> this wouldn't be as noticeable.

On a rough trail, no nasty behavior will be noticeable, the whole ride
being full of vibration and bounce.  It is under these circumstances
that the axle will move from braking and the same circumstance that
will obscure any change.

> But it occurs to me there IS a way to test this theory withOUT
> anyone risking life and limb (at least no more than they normally do
> when riding downhill on a MTB).  It seems to me that a simple, cheap
> AND effective method to test the "QR moving" theory would be to
> simply properly install the front wheel, then put a small dab of
> fingernail polish (or white-out or paint or glue) between the
> junction of the QR and dropout.  Any microscopic movement will
> fracture the "seal" and make it obvious that there was movement.

That is correct.  However, all these suggestions and the one about
changing the dropout angle dodge the issue that there is a reversal of
force from upward to downward on the axle and that that alone is
unacceptable because the force is great enough to cause motion, quite
aside from the greater force being toward separating the axle from the
fork.  Even a closed-eye fork end would present a hazard because it
had a reversing force on it.  This is similar to the pedal to crank
attachment that causes crank failures because it moved no matter how
tight it is made.

What needs to be done is, either put the caliper in front of the fork
leg or use automotive style lug nuts to secure the axle.  Such
fasteners are designed to take forces in all directions without creep.
If you look at history, it took the automobile business about 40 years
to recognize this even though wheels were often lost underway.

> The beauty of this test is that those who would perform it would be
> VERY sure about the status of their QR before they performed the
> test.  They'd also know with absolute certainty whether or not the
> QR "began" to move, and they wouldn't have to resort to dangerous
> and invalid tests like riding around with loose QRs.

Do the test!

> So what say - are there any of you out there with disc brakes,
> downhill bikes, QRs, a dab of paint an a day to ride?

I don't have such a bicycle but I ride lots of trails on hard tires,
hard enough to make spokes twang from hard landings and braking hard
enough to raise the rear wheel.  I don't have QR concerns even though
they aren't especially tight.  The jam nuts are smooth faced and the
dropouts have no retention lips... but I use rim brakes.

http://www-math.science.unitn.it/Bike/Countries/Europe/Tour_Reports/Tour_of_the_Alps/Gallery/103-0339_IMG.JPG

Jobst Brandt
jobst.brandt@stanfordalumni.org

Date: Fri, 26 Mar 2004 19:00:13 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <4063ff29$0$23537$44c9b20d@news3.asahi-net.or.jp>

Mark Hickey wrote:

> As far as the industry as a whole is concerned, there *is* a threshold
> at which the potential cost of failures exceeds the cost of fixing a
> problem.  If the problem is at the 1/1,000,000 fork level a
> manufacturer might conclude that they'd be better off ignoring the
> problem since the redesign would likely cost more than the potential
> liability.

I am shocked that a manufacturer could be so wholly ignorant of the law.
  Obviously this explains your attitude, but it does not excuse it. I
suggest you take a look at the CPSC web site and the CPSA:

"Under the Consumer Product Safety Act (CPSA), manufacturers, importers,
distributors, and retailers must immediately report information about
potentially hazardous products to the Commission."

"This settlement puts companies on notice that they must notify CPSC
without delay when they learn of product hazards or consumer injuries,"
said Commission Chairman Hal Stratton. "We intend to enforce these
requirements vigorously and there will be serious consequences for
companies that fail to report such information quickly. The Commission
will investigate and seek penalties against those who violate federal
safety laws."

"If in doubt, companies should always report any and all information to
the Commission that could affect the safety of consumers," said Chairman
Hal Stratton. "Companies that fail to take such an approach expose
themselves to the risk of civil penalties."

"Judge Keep noted that not knowing about the statutory requirement, not
understanding the defect, or blaming the problem on consumer misuse do
not excuse a company from the requirement to report a hazardous product."

How does the recent brushing aside of a rider with a dangerous fault (as
described by Avid) square with that?

And before you simply retort that the CPSC has looked into it, and found
no cause for concern, remember that this is based on a report by
LaPlante which "proves" that there is NO risk of a failure, and the
manufacturers all insisting that they have NEVER come across a SINGLE
case. Lying to the CPSC is also an offence for which one can be sent to
prison.

James

Date: Fri, 26 Mar 2004 20:31:42 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <4064149b$0$23535$44c9b20d@news3.asahi-net.or.jp>

Ben Cooper - Kinetics wrote:

> So, which manufacturer would you like me (an owner of a small Scottish
> bike company) to have a word with?

The one who made the fork you used in your test. As you know, all the
major manufacturers claim they have never heard of a single user ever
having any similar problem with their forks, so your _unique_ experience
will undoubtedly be fascinating for them. Please let us know when they
give you the standard "actually you are the first person to bring up
this issue" brush-off.

By all means talk to the skewer manufacturer if you think it may be
faulty, but you must be aware that there are straightforward standards
to which they should adhere and (as far as I am aware) all commonly
available skewers pass these tests. None of them are designed to take a
very large load, and in a competent design they would not see one.

I realise it doesn't quite apply in your case, but if you were (a) in
the USA and (b) actually selling forks like that, you would be risking a
  punitive fine and even jail sentence for not reporting something that
you KNOW to be a dangerous design error. I've had email from a USA shop
owner who has also seen the problem for himself and is very worried
about his liability, but does not feel he can "go public".

> The person I'd really like to have a word
> with is the person who built your original tandem...

Rock Lobster, USA (the fork, not the frame). Feel free to CC me with
your correspondence if you like. He made a mistake, apologised and no
serious harm was done, which is why I didn't feel the need to take it
any further (I was a bit pissed off he didn't immediately offer to cover
our resulting costs, but I can't be bothered suing him over $200). If
the major manufacturers had behaved similarly, this would have been over
very quickly as far as I am concerned.

James

Date: Fri, 26 Mar 2004 22:44:49 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <406433ce$0$23536$44c9b20d@news3.asahi-net.or.jp>

Tony Raven wrote:
> James Annan wrote:
>
>>Mark Hickey wrote:
>>
>>
>>>As far as the industry as a whole is concerned, there *is* a threshold
>>>at which the potential cost of failures exceeds the cost of fixing a
>>>problem.  If the problem is at the 1/1,000,000 fork level a
>>>manufacturer might conclude that they'd be better off ignoring the
>>>problem since the redesign would likely cost more than the potential
>>>liability.
>>
>>I am shocked that a manufacturer could be so wholly ignorant of the law.
>>  Obviously this explains your attitude, but it does not excuse it. I
>>suggest you take a look at the CPSC web site and the CPSA:
>>
>
>
> I think you are over-reacting to what Mark said and misintepreting what the
> CPSC are requiring - and I speak as someone who has spent a good portion of
> their life under the oversight of the far more rigourous Food and Drug
> Administration working in their highest risk category as the person where the
> buck stopped.  You can calculate the probablility of a loss of all engines on
> a commercial airliner - it is finite and it has happened.  It does not mean
> that you need to add more and more engines (the probability still remains
> finite).  The certification of twin engine jets for transatlantic flights was
> based on showing the probability of twin engine failure was acceptably low,
> not that it was zero.   A lower level of risk could have been achieved by
> denying their certification and continuing to allow only four engine jets
> (which have had incidents of four engine failuires).   CSPC, FDA, FAA etc are
> all about risk management - risk can never be reduced to zero so its always
> about minimising risk as far as is reasonably possible.

Sure, but it is made explicitly clear that the ultimate decision where
to draw the line in this "risk minimisation" is the responsibility of
the CPSC and not the manufacturer or retailer. The industry does not
need "proof" of a "significant" problem, they need reasonable grounds to
suspect that there may be one. Last month, someone phoned them up with a
clear description of an obvious hazard, which was immmediately
recognized as such by Avid, and he was given a perfunctory brush-off by
two fork manufacturers. Ben Cooper has also demonstrated clear proof of
an obvious hazard and he refuses to "officially" tell the manufacturers
precisely BECAUSE he knows they will have to act and he fears the
consequences. The fact that this is plastered all over the internet
makes the situation more than a little farcical, of course. If the CPSC
decides that the risk is small enough to be acceptable, then so be it.
That is not my fundamental bone of contention. Their current assessment
is based on the claims by the manufacturers that NO-ONE has EVER
experienced ANY problems of this nature, which is self-evidently false,
however much dispute there is as to its extent or seriousness.

As for the calculation Mark Hickey proposes, it is illegal, pure and
simple. Plenty of people have been sent to prison for insufficiently
prompt notification of a hazard - have a look at the CPSC press
releases. I'm sure he doesn't apply such standards in his business, of
course, but it shocks me to think that he could suggest that it is in
any way acceptable.

James

Date: Sat, 27 Mar 2004 05:51:54 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <406497e7$0$23542$44c9b20d@news3.asahi-net.or.jp>

Mark Hickey wrote:

> But does the manufacturer report to the CPSC every time a handlebar
> breaks?  I doubt many would

Do they say "actually you are the first person to bring up this issue"
and then ignore it? Do they quite deliberately and cynically build up a
myth of "always operator error" in order to dissuade reports and get
themselves off the awkward hook of having to investigate those that they
get?

> The testing I propose would indicate that (for whatever reason) the
> skewer CAN unscrew (or at least "begin to unscrew"), which would put
> the issue in an entirely new light, IMHO.

Ben has already proved that the skewer CAN unscrew. I thought you had
already admitted as much, but were insisting that it has to be a
"significant" failure rate, according to some definition of "significant
that you have persistently refused to define.

James

From: jobst.brandt@stanfordalumni.org
Subject: Re: "Actually you are the first person to bring up this issue"
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Message-ID: <Wzk9c.2221$Fo4.23949@typhoon.sonic.net>
Date: Sat, 27 Mar 2004 19:26:46 GMT

Tony Raven writes:

> Jobst, any chance you, as someone in the US, could put in an FOI
> request to the CPSC for that "covered up" Cannondale report and
> perhaps we can see whether there is anything of merit in it.  James
> seems to feel that an application from Japan may not be fulfilled.

I don't believe I am a good one to make this approach, not having
anything to do with bicycles with disc brakes or having personal
connections with anyone who might be injured by such a failure.  Just
understanding the problem is not a good position to raise a complaint.
It is not as though the CPSC doesn't know about it.  It needs to have
a constituent raise the issue.

I just submitted a report with qualifications as I see it to the CPSC.

I am disappointed that the CPSC hasn't taken the issue and
investigated it independently of knowledge of injury.  The hazard is
so technically obvious to people who understand mechanical dynamics
that I don't understand how they can ignore this.  However...

Just to cite an even greater but non related brake hazard that I
approached with appropriate authorities.  As often occurs, these
people did not look at the essence of the problem but rather "who
are you?"  something we are seeing right here.

Cable cars in San Francisco have no functional emergency brake and
runaways with passenger injury and death have occurred over the years,
and each time the lack of a means to stop the car before it collided
with cross traffic at the bottom of the Hyde Street hill was ignored.
This occurred mainly because mechanics who used cutting torches to
free the "steel wedge emergency brake" from the cable slot marveled
how well the feature "stopped" the car.

Meanwhile, that a steel wedge with less than a square inch contact on
a steel slot is not a brake, it having no means for dissipating energy
(brakes get hot) was overlooked.  Molten steel on steel slides better
than grease in the same interface, a cable car having sufficient mass
to sustain the melt until it collides with a vehicle and comes to rest.

The same lever that actuates the wedge could easily be reconfigured to
press a rubber tread against the street to come to a skidding halt as
motor vehicles do on these streets.  Besides that, I outlined two
features that cause these runaways, specifically the Hyde Street hill,
the steepest and longest hill.

Grip men, in an effort to not jerk the riders with quick acceleration
after the car stop just before the sharp crest of the Hyde Street
hill, gradually engage the cable.  A cable car that is not up to the
9.5mph speed of the cable is operating under partial slip.  As the
grip takes hold it must lift the cable off the support rollers under
the street and the crown wheel on which it rides over the crest of the
hill.  This action easily peels the cable from the grip, especially in
the morning when a grip does not yet have a deep pocket from wear.
Grips get new friction jaws regularly.

After writing letters to people in charge and sitting down with the
operators union chief, one of whose grip men was being given the blame
for a runaway, I never heard another word nor could I reach anyone by
phone.  There was no response in writing.

Today, cable cars must wait for a green light before the top of the
Hyde Street hill that indicates that all cross traffic has been
stopped on Bay Street at the bottom of the hill and that in case of
losing the cable, the car can shoot through the intersection "safely".
There still is no functional emergency brake, although the big red
lever next to the grip lever is touted to have enormous holding power,
so much so that cutting torches have been required to loosen its grip.

Jobst Brandt
jobst.brandt@stanfordalumni.org

Date: Sun, 28 Mar 2004 07:51:40 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <406605b0$0$23541$44c9b20d@news3.asahi-net.or.jp>

Tony Raven wrote:

> I suspect the reason nothing has happened is because the manufacturers are
> obliged to report to CPSC serious accidents or near accidents that are
> reported to them and there is not a pile of accident reports sitting on CPSC's
> desk on this one.

I did explain all this last year, but the journalists did their
nudge-nudge-wink-wink routine and assured everyone that there was no
need to kick up a fuss because the manuacturers would do the decent
thing and solve the problem all on their own. You can see how right they
were...

>  Does anyone here know anyone that has reported a serious accident
> or near accident to the manufacturer or CPSC from this cause?

Does a slipping QR constitute a serious fault? Avid thought so, but the
fork manufacturers brushed it off wih "no-one round here has that problem".

James

Date: Sun, 28 Mar 2004 08:04:24 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <406608ad$0$23541$44c9b20d@news3.asahi-net.or.jp>

Tony Raven wrote:


> I
> look forward to reading what you receive in due course on the web site

I'm not a performing bear, and I am tired of jumping through hoops for
the sake of it. Plenty of people have professed a genuine interest in
solving this problem, let's see if any of them put in a request. I have
already asked twice, Carlton Reid (bikebiz) also asked and was rebuffed.




[space left for embarrassed silence, in which various readers shuffle
around looking at their shoes]




FWIW, I already know that the report is a whitewash, it would perhaps be
a little embarrassing to LaPlante to seee how inefffectually he
investigated the problem but I do not believe that viewing it would
really further the matter materially. I merely pointed out that it was a
whitewash that was being concealed from public view. As I said last
year, this problem will be rapidly solved when a handful of ordinary
riders report their problems. One person with a slipping front wheel has
kicked up more of a fuss than anything I have done in the last several
months.

James

Date: Sun, 28 Mar 2004 20:53:39 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <4066bcbf$0$23535$44c9b20d@news3.asahi-net.or.jp>

Mike Jacoubowsky/Chain Reaction Bicycles wrote:

> I relayed reports of this issue, several months ago (when it first appeared
> here), to a major manufacturer.  Just because one of my customers hasn't had
> the issue doesn't mean it doesn't exist, and it would be irresponsible not
> to tell them about this thread.  So, of course, you're wondering what they
> said, yada yada yada.  In a nutshell, if there is an issue, it hasn't risen
> about the noise level (meaning that it hasn't called attention to itself).
> If you're a manufacturer, you have to prioritize your efforts and deal with
> what's in front of you.

Actually they did spend a fair bit of time looking in to this
"theoretical" problem. Trek certainly promised to look into it (but we
only ever heard from their lawyer). LaPlante looked into it long enough
to produce a report "proving" that it is impossible, and the ASTM
promised a "simulation exercise" testing QR retention and had a whole
meeting discussing it. Velotech managed to find a problem, so did Ben
Cooper in his back garden, but the engineering might of Rockshox,
Marzocchi, Manitou, Fox and the rest were baffled as to what all the
fuss was about.

Given this apparent chasm between their experiences, and the substantial
number of independent experts who appear to be convinced of the problem,
what would a reasonable person do? Would they actually try to find
anyone who had experienced the problem, like the people I quote on my
website, or Lennard Zinn in Velonews who describes his own experiences
of a slipping QR, or the author of that MBR article who had a QR come
loose no fewer than 6 times? Would they talk with the Velotech lab, or
even stoop to the plebeian level of looking at the singletrackworld
website, and doing a search for "loose qr" on the forum? What do you think?

I haven't told you yet about the USA bike shop owner who told me last
summer that he had seen the problem himself regularly in his own stock,
and would raise it with the manufacturers. I never heard from him again,
and I'm not surprised that he is more than a little worried about
"coming out" in public. He told me:

"I can't believe that someone at a magazine, or company has not seen a
front wheel on a single bike turn just a little crooked while out on a
ride when using a disc brake system.  I see it often enough."

"Most all of the forks, discs I deal with have deep lawyer tabs, and so
far have been used by riders that will out of habit check and reposition
the front QR after a long or steep descent, if the group gathers up to
chit chat, etc it just seems to be habit to check the QR on disc bikes,
in my group.  The concerning thing is that there usually is at least one
person in the group that needs the QR adjusted/tightened."

And what did the manufacturers do when someone popped up last month,
saying "hey, I've got this problem you've been unable to find for the
last year"? A problem, you may recall, that was immediately
characterised as too dangerous to ride (by Avid). Did they jump at the
chance of examining this curiosity? Did they hell. They said they had
never heard of it, told him no-one ever had that problem round their parts.

I'm astonished that you still claim that this state of affairs is all
_my_ fault for not generating yet more data. You are bending over
backwards to defend the indefensible in their case, and pick the most
insignificant of nits in mine. They have not seen the data because they
are holding up their telescopes to blind eyes.

James

Date: Wed, 31 Mar 2004 06:40:39 +0900
From: James Annan <still_the_same_me@hotmail.com>
Newsgroups: rec.bicycles.tech,uk.rec.cycling,alt.mountain-bike
Subject: Re: "Actually you are the first person to bring up this issue"
Message-ID: <4069e953$0$23541$44c9b20d@news3.asahi-net.or.jp>

Tony Raven wrote:


>  Specialized have already had a
> recall for mounting tab failures.

When?

If you mean the recent recall of bikes with too large a rotor installed,
there were NO failures and no evidence that there ever would be any
failures. The problem was merely that the combination had not been
properly checked.

Puts the current situation regarding disks and QRs into context, don't
you think?

James

From: jobst.brandt@stanfordalumni.org
Subject: Re: please tell me all about braking
Newsgroups: rec.bicycles.tech
Message-ID: <%p%ac.3181$Fo4.34635@typhoon.sonic.net>
Date: Thu, 01 Apr 2004 21:00:43 GMT

Tim McNamara writes:

>> I can see I'll have to borrow a digicam.  Just got back from
>> another sketchy downhill.  Still absloutely zero shifting of the
>> q.r.  My fork's been disk braked 2 or 3 times a week for well over
>> a year now.

> And you haven't adjusted or reclamped the QR in that entire time?
> Amazing!

I'm not amazed.  I visited our local bicycle shop recently and wanted
to see how severely a wheel locks when the left end of the axle is
ejected by the disc brake.  First, I was amazed at the small diameter
of the disc whose working radius was 1/4 the tire radius, which makes
the ejection force as much as 4x rider weight.  Anyway, when I tried
to open the QR, it was so tight that it took all I could do to open it
without tools.  I guess people are aware of suspension fork-disc brake
loosening syndrome.

Jobst Brandt
jobst.brandt@stanfordalumni.org