"Actually you are the first person to bring up this issue"

wrote in message ...
James Annan writes:

Because of all the people who have experienced the problem, some
have been convinced that it was "probably" their own fault, some
have been assured that something is being done and there is no need
to make a fuss, some don't want to face the vitriol and abuse that
will undoubtedly come their way if they do make a complaint in
public, and some have simply upgraded to a bolt through fork and
thought nothing more of it. A few weeks ago, someone decided to
actually do something, hence this thread.

This reminds me of the way spoke failures were once treated. Then
snapped spokes were attributed to riding off a curb or hitting a pot
hole, fatigue failures, at that time, being unknown to the bicycle
business in general. Today no longer known that most of what is
explained in "the Bicycle Wheel" was not understood at the time of
publication and spoke failures were generally attributed to rider
misuse.

Because somebody actually took the time to analyze DATA, and actually
look at the failure modes. With controlled testing, or materials
analysis of failed components.

Who might that have been, hmmmm?

And where is that detailed analysis with respect to so-called disk
brake ejections? The German lab has not released the full data set,
from what I can find. Maybe somebody has a copy, and is willing to
share.
--
Robert Jones

Tim McNamara wrote in message ...
(Jonesy) writes:

Tim McNamara wrote in message ...
(Jonesy) writes:

James Annan wrote in message
...

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.

Assuming, of course, that there actually *is* a problem.

There's no doubt that there is a problem.

That depends on how you define "problem," and where you draw the
line.

The problem is that current front disk brake design results in an
ejection force being applied to the wheel under normal operation.

If the wheel does not actually come out of the drop-outs, then it's
less of a problem and more of a design compromise. But that's mere
word play.

There's no doubt that this force exists, both in free body diagrams
and simple experiments anyone can try.

I'm not sure where you get the idea that I question that the force
exists. I will now allege that you are attempting to set up a
strawman to defend your position, considering the part that I wrote
about QRs to be *completely missing* from your response.

This is not anecdotal, it's
readily and objectively demonstrable. You could prove the existence
of this problem in less than 60 seconds.

The stories of wheel ejection due to this "problem" are indeed
anecdotal. We do not know the initial conditions. In fact, one can
almost guarantee that the accounts have an assumed *lack* of operator
error. This *in and of itself* discredits the value of the accounts.

So, there is a problem and there is no doubt about it.

This is your *opinion*, not fact.

his *is* a
design flaw and a dangerous one at that.

This assumes that wheel ejection will inevitably happen. An untenable
position that you cannot hope to prove.

The industry needs to fix it
post-haste or they *will* suffer the consequences of millions of
dollars in punitive damages sometime in the future.

This assumes, again, that wheel ejection is certain.

I draw the line in real-world application, not at the force-diagram
level. I just plain don't accept anecdotal evidence as proof. As
support of hypothesis, yes. As proof? No. There is a difference,
and it is real.

Well, then, do the very simple experiment with your disk brake
equipped bike and prove the existence of the problem to yourself.

I have read this half-assed experiment several times, and I will
repeat:

It is invalid for testing the system as used. Remove the air from
your car tires. Drive around until the sidewall fails. Fatal flaw in
the design!

All sarcasm aside, how the wheel is fixed into place makes all the
difference.

The
front disk brakes creates an ejection force in normal operation.
That's as real-world as it gets.

Whether the force results in an actual ejection is UNKNOWN.

Read that over and over and over until you grasp the implications of
it.

The only question is how often it happens.

That's a very pertinent question. If it doesn't happen often, then
it's hard to define it as a problem.

The ejection force occurs every time the brake is used. Every time.

Now I know you are purposely misreading what I wrote in order to
create your strawman.

Remove the word "force" from your sentence. Now see how it fits with
what I wrote.

Every single time. I would hope that seems clear enough. The
question of how often a wheel is ejected is important in the
epidemiological sense, but from the standpoint of competent design
the issue is moot.

LOL. Hardly. If the wheel never comes out, then the "design flaw" is
purely theoretical!

there is no way that it is acceptable that the
front brake creates this ejection force- which is of surprisingly
large magnitude, exceeding the minimum clamping force requirements
under the CPSC rules as has been previously discussed.

This is only true if and only if the fork legs are independent of one
another. They are not, in ANY fork design. In addition, testing of
QR skewers has shown that the vast majority exceed that minimal
standard.

This is
incompetent design, pure and simple.

I will agree that it is a compromise. Not ideal, for certain. Guess
what - almost all bicycle products are design compromises. That's why
stems break, seatposts snap and frame welds fail.

I agree that to the poor folks who experience catastrophic failure,
it is a very serious problem. But to those folks who go year after
year after year without any sort of evidence of difficulty, then the
problem just plain doesn't exist.

How many people with quadraplegia, traumatic brain injury, or who are
just plain dead as a consequence of this design, are acceptable to
you? People went year after year without being decapitated by plate
glass windshields before safety glass was required- does that mean
there was "no problem" with the use of plate glass in windshields?

The appeal to emotion is a logical fallacy in and of itself.

The acceptance of risk is part of the human experience. I am more in
danger in my car than I am at any time on my bicycle,
disk-brake-equipped or not. Save your teary-eyed drama - it has no
place in a technical discussion.

It'll be nice to see all that wonderful, properly-controlled data
from the laboratory testing.

Think of it like Microsoft Windows: *you* are the testing lab.

This is a diversionary argument. Controlled testing will answer the
question. Until then, proof doesn't exist. If one were to give
weight to the anecdotal evidence, then I would have to judge "no
problem" to be the norm, and "problem" to be in the vast minority.

Perhaps I am just unwilling to bury my head in the sand and to adopt
the attitude of "well, it hasn't happened to me so it's all right."

Nor should you. Nor should you grasp at straws and pretend that a few
accounts mean anything as far as actual data goes.

This is a serious problem with the potential to be life threatening;
it is unacceptable and needs to be corrected.

Merely your opinion.

If the design cannot be
corrected then it should be removed from the market and all existing
installations of this equipment should be recalled and replaced.

*IF* independent testing discovers that, I will agree 100%. But if
there are mitigating factors, and this phenomenon is limited to a few
select conditions, then I would not go so far as a total recall.
Again, if the wheel is never ejected, then the "problem", effectively,
does not exist.

The
designers and manufacturers of these products should have spotted this
problem before the first fork was made. It's not like this is obscure
and arcane knowledge.

It is not as clear cut as you want to believe, either. Your opinion
is not fact, nor is it very meaningful in the debate, UNLESS you have
hard data that you wish to share.

I don't want opinion, or anecdotal evidence, or supposition from
climate professionals pretending to be engineers. Proof comes in the
form of repeatable experiments, performed with the proper controls.
Until that time, I will regard Mr. Annan's pursuit with all the
attention it deserves.
--
Bob Jones

Super Slinky wrote in message et...

He and Jobst Brandt think that everyone besides them are too stupid to
understand their sophomoric force diagrams.

Step forward Adrian Carter of Pace Racing, and Bob Davis of AriZona
Cycles, both of whom make disk brake + QR forks, and both of whom are
on record as claiming that a disk brake cannot eject a wheel even
without a QR present at all.

The typical bike has a dropout angle more or
less parallel with the head tube. On my bike this means that using the
brake pad as a pivot, the axle hits the dropout at about a 45º angle,
which nullifies about 70% of Mr. Annan's ejection force.

Bzzt. Wrong, thanks for playing. But don't flatter yourself by
pretending that this is a "sophomoric" error, I'd hope that any
reasonably bright 15 year old schoolchild would be able to set you
right.

And in
spite of the arrogance of James and Jobst that nobody understands their
techno-babble, the truth is quite complex and nobody knows everything
that is going on down there.

Wait! First it's "sophomoric", but now it's too complex for anyone to
understand. I see lots of people throwing up a smokescreen of petty
trivia to do with "substandard QRs", knurling, the diameter of the
hole in the hub body, but the essential details are clear and
straightforward.

Even if somebody was to do a first class physics research paper on the
subject, it would merely be an academic exercise, because we have a
better method for gauging the danger: real world experience.

Like the real world experience listed on my web page? Somehow that
gets the snide dismissal of "anecdotal" when it doesn't suit your
purpose.

Why doesn't everyone who is worried about
this just switch to a through-axle fork? Beats me. I guess it isn't as
much fun as bitching and whining.

Beats me why the manufacturers don't say that their disk brake + QR
forks are not suitable for use. I guess it isn't as profitable as
selling them, and then selling an upgrade as the rider finds out his
wheel won't stay in place.

James

"tcmedara" wrote in message
news:26p7c.20734$Cf3.17366@lakeread01...

James is an ordinary bloke. He has raised what you acknowledge to be
a valid concern. Where is the evidence that this valid concern has
been treated with appropriate seriousness by those who (a) make money
by selling the product abnd (b) have the resources to conduct more
rigorous tests?

That's a whole different problem, and one I could agree with you on.
Based
on the current facts, this may be worth looking into. Annan did contact
the
CPSC and was told they didn't see a problem, despite the facts that he
offered. Other than Annan not liking the answer, why shouldn't we accept
that answer from the very agency charged with the protection of consumers
in
the US from defective products.

So you've had a serious crash, a friend is paralysed for life, a number of
experts agree with your analysis that there is a problem and, lacking the
necessary resources, you contact the consumer safety body. They come back
and say not to worry, they've asked the manufacturers and they say there
isn't a problem, but provide zero evidence to back this up.

You are clearly satisfied by this response. The fact that most of us would
not be says, I think, more about you than about us.

The burden of proof should be on Annan in
my opinion, not the CPSC. They looked at it, they said "no problem", so
what more should they do?

Provide some evidence to suggest that rather than ignoring it they have done
some kind of analysis. This is not a theoretical problem, it is a problem
which is being reported by actual cyclists in the real world. In fact, two
problems: QRs coming loose under repeated braking (not considered a problem
with rim brakes) and an ejection force applied by the brake. The burden of
proof should be, as always, with the suppliers of product to demonstrate
that it is safe. Part of that means showing, where a valid concern has been
raised, that it has been considered in due detail.

The letters on James' site represent well-respected technical experts
agreeing that there is a case to answer, cyclists agreeing that there
is an apparent problem (two, actually, QR loosening and ejection
force), and the major US public safety body doing f**k all.

Key words -- there is a "case to answer" and "apparent problem" Poor
basis
for policy formulation.

But excelelnt basis for requiring some kind of proof that the product is
safe. Proof which, a year on, is still absent. Which tells us something, I
think.

As previously suggested, google on Ford Pinto fuel tank fires for
details why that assumption is known to be false.

I'm sure there's a spectrum of behaviour. Some companies will try to
obfuscate, others will step up do what needs to be done. Surf around the
CPSC site and look at the breadth of recalls going on across the country.
Not all companies are engaged in nefarious deeds to cover product
shortfalls.

Companies may engage in different behaviours in different circumstances.
The keyt is what their lawyers advise them to do. If they recall disc
brakes, for example, will that bring hundreds of crashed mountian bikers out
of the woodwork claiming for dental work and punitive damages?

The lack of a single credible rebuttal is no grounds form an indictement.

Actually it would be quite good grounds for an indictment in this case,
given the quality of evidence and opinion supporting James. Whether that
indictment would result in conviction is another matter.

I don't think any company can survive long if they are forced to
rebutt any and all criticisms posted on every web site out there.

I have had two frame failures on my recumbent. The manufacturer subjected
the first to extensive metallurgical analysis, and took pains to ensure that
I was supplied with a replacement. By the itme the second failure
happened - only the fourth in total out of all the bikes sold - they had
changed the grade of aluminium used, unpgraded the headset, changed the
manufacturing process and reinforced the area where the failure occurred.
They did that based on three failure, with no injuries. Here we have at
least two failures documented in detail, one ending in severe injury, and
numberous "me-too" incidents.

At the
risk of promoting lawyers, that's really where the courts come in.

No it's not. Courts are for recriminations. I think the guys involved
would be perfectly satisfied with an engineering solution to prevent a
recurrence of the problem, no lawyers involved. I have a view that it is
the lawyers who are preventing a more open discussion of the issues.

have you ever heard of a single front wheel
ejection (as opposed to a wheel falling out under gravity due to being
unsecured) on a rim-braked bike? They've been around for a century or
so, so there should be plenty to choose from.

It's not about what I may or may not have heard of. Your question is
valid,
but remains (like this whole debate) in the realm of the theoretical.

No, the debate is not theoretical. James' wheel ejected catastrophically
causing him to crash. So did Russ', with disastrous consequences.

Are there actually more wheel ejections
now, or are they just more apparent to those looking for them?

As stated: what is the mechanism by which wheel ejection could be caused in
a rim-braked bike? This issue is specific to disc brakes.

--
Guy
===
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

x-no-archive: yes
X-Newsreader: NN version 6.5.0 #2 (NOV)

"tcmedara" writes:

I may be stretching the analogy a bit, but the point remains --
until there is statistically significant evidence of correlation between
front wheel ejection and disk brake use, there's nothing to act on. There's
no "problem" that needs to be solved -- by either the gov't regulatory
agencies or the manufacterers. I'll be the first to change my tune if a)
someone can demonstrate a cover-up, rather than just assert one; and b) show
that the QR/disk effect is resulting in real incidents out on the trail.

Extremely good point. It occurs to me that all this fuss that cyclists
make about broken glass, thorns, etc., is similarly just anecdotal
evidence unsupported by any properly controlled large statistical
study. And even if it turns out that broken glass does cause
punctures, do punctures necessarily lead to injurious accidents? At
the moment bicycle accident hospital records don't always record the
necessary information. We need a proper epidemiological study to
establish just how many people actually do get injured as a result of
punctures caused by broken glass. Until we have such data we really
don't know if broken glass on roads and cycle paths is a problem.

--
Chris Malcolm +44 (0)131 651 3445 DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

"Slacker" wrote in message
...

Forgive me, but I'm still a little confused. If the wheel is installed
properly there is no problem, so what issue are we talking about?

Almost any item can be misused a little and remain safe.

Are you guys just trying to cover every single possible act of
incompetence and/or stupidity?

Nope. but tight enough QRs to be perfectly OK for a rim-brake bike will
potentially be dangerous with disks.
This is hardly a great act of stupidity or incompetence.

Just zis Guy, you know? wrote:

So you've had a serious crash, a friend is paralysed for life, a number of
experts agree with your analysis that there is a problem and, lacking the
necessary resources, you contact the consumer safety body. They come back
and say not to worry, they've asked the manufacturers and they say there
isn't a problem, but provide zero evidence to back this up.


I would like to emphasise that this isn't just about Russ Pinder,
although of course his case is well publicised. It isn't even about the
other serious crashes I have heard about, several of which required
hospital stays and lengthy rehab. From my POV, it's about the _next_
failures, which are readily preventable.

Companies may engage in different behaviours in different circumstances.
The keyt is what their lawyers advise them to do. If they recall disc
brakes, for example, will that bring hundreds of crashed mountian bikers out
of the woodwork claiming for dental work and punitive damages?

One thing is pretty certain: the manufacturers will not open themselves
up to a large number of compensation claims when they finally admit
there is a problem. No-one is pretending that a large number of cyclists
have been hurt by this, but clearly a modest number have been. For all
the pre-emptive vitriol about ambulance-chasing lawyers, the only
lawyers that have been heard from so far are those of the manufacturers,
issuing their predictably evasive denials. Frankly, if they were worth
their salaries, they should be warning their bosses of the unlimited
punitive fines and even prison sentences that they could face were any
evidence of a cover-up or concealment come to light. Just in case anyone
is in any doubt about the matter, manufacturers and retailers have an
absolute duty to report any _suspicion_ of a problem to the CPSC (rather
than waiting for conclusive proof sufficient to convince the most
obstinate).

According to my recent correspondent, Avid technical support said:

"You most certainly have a big problem with your fork dropouts and/or
the QR. I'd get this fork/QR issue handled before you ride any further."

Yet the fork manufacturer (two of them, in fact) brushed him off with
denial and advice to try a better QR (he was already using Shimano).
They are treading a very dangerous path here.

James

A Muzi wrote:


But the one case
where a wheel actually left the fork has a very unusual fork end,
exactly wrong, and also lacking LLips.

I'm puzzled as to what motivates people to make statements like this
which are so obviously false and trivially disproven.

There are _several_ cases of wheels leaving the forks mentioned on my
web pages (and the linked STW threads), and only two of them involved
tandems with badly angled dropouts and no lawyer lips. The rest were all
standard commercial MTB forks.

James

tcmedara said...

Couldn't bear to trim it.

I do believe you have said it better than I ever could. And it's just the
sort of thing I was trying to get at. I'll take your implied advice now and
just drop the subject. It's quickly turning into a Mike Vandeman-like
discussion but without the humor. I'm always suspicious of self-righteous
indignation and claims of martyrdom at the hands of government and big
business. It's usually just a smoke cloud for some one looking to obfuscate
the cracks in their own argument. I see we both came to similar conclusions
independently. You think the oh-so-objective Mr Annan will ask to post your
analysis on his site so readers can make up their own minds? Let us know.
I'm not all that hopefull

Tom

I won't hold my breath about him publishing any point of views except
his own. He seems to have a...mental block against anyone's opinion but
his own. Besides, I have been kind of hard on him, but from where I sit
he invites derision because of his own snide comments which he calls
'irony'. I wasn't necessarily implying that you give up the argument.
God knows I have argued about things far past the point of doing any
good, but you may help preserve your peace of mind if you accept the
fact that he isn't going to be persuaded by anything you say. I just
jumped in because I hate to see anyone fight the good fight alone.

Tom Sherman said...

Super Slinky wrote:

...If the dropout was angled
about 45? forward, there would be no ejection force at all....

Then why not design forks with disc brake mounts with this dropout angle
to avoid the problem completely?

I have always been willing to concede that James had a point, just not
as good a one as he thought it was. The current design isn't ideal and
could use some refinement. But considering all the failures possible on
a mountain bike, it isn't anything to get excited about.