x-post: Bike Biz: Wheel ejection theory goes legal

I once partially ejected the rear wheel on my road bike. I had only
had the bike for a few days and knew that I should check the skewers
for proper tightness but it always slipped my mind whenever I took it
out for a ride. As luck would have it I ended up bring cut off by a
poor driver and I had to make a panic stop from about 20mph that
lifted my rear wheel high, almost doing an endo. I brought on the rear
brake hard after the rear wheel had lifted and that provided the
opportunity for the rear wheel to pop out of the drive side dropout. I
then slammed back down on the rear wheel before I could unclip and
demount the saddle to land on my foot. This bent up the skewer and put
the wheel out or true but it was still rideable with the brake left
open. Lesson learned: always adjust the skewers on a new bike, even
one from a good LBS.

Martin Dann wrote:
-previously snipped-

jim beam wrote:
it's just legal ambulance chasing by those who aren't analyzing the
full
picture. yes, disks cause a resolved force in the direction of the
open
end of a dropout. but since this force is exceeded 3 or more times by
the retaining force of a properly tightened skewer, it's an argument
without merit. as evidence by the lack of actual ejections.

"Roger Thorpe" wrote:
Ummmm... "Correctly tightened" seems about right, but have you had a
rear wheel pull over under acceleration because the QR wasn't tight
enough? The forces are comparable (probably lower). It's happened to me,
and i'm not exactly an inexperienced cyclist.

* * Chas wrote:
Last year I had that happen on 2 old bikes that I had just worked on. Both
had older Shimano rear hubs; one was a Dura-Ace skewer and the other a 600
series. I've used QRs for over 35 years and only had a rear wheel pull
over happen a few times before. The only thing that I could find was the
serrations on the QR lock nuts weren't very prominent. I switched the
skewers to Campy, end of problem.

Shimano steel skewers are of comparable quality. Next time, try oil on
the cam first before replacing it.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

In article ,
jim beam wrote:

it's just legal ambulance chasing by those who aren't analyzing the
full picture. yes, disks cause a resolved force in the direction of
the open end of a dropout. but since this force is exceeded 3 or
more times by the retaining force of a properly tightened skewer,
it's an argument without merit. as evidence by the lack of actual
ejections.

You were shown the math a couple of years ago that clearly showed that
the ejection force could readily exceed the retention force at realistic
decelerations. At that time you just disappeared out of the subsequent
conversation.

And as you neglect to note, actual ejections have been reported.

Tim McNamara wrote:
In article ,
jim beam wrote:

it's just legal ambulance chasing by those who aren't analyzing the
full picture. yes, disks cause a resolved force in the direction of
the open end of a dropout. but since this force is exceeded 3 or
more times by the retaining force of a properly tightened skewer,
it's an argument without merit. as evidence by the lack of actual
ejections.

You were shown the math a couple of years ago that clearly showed that
the ejection force could readily exceed the retention force at realistic
decelerations.

that's strange. i recall it like this:
1. annan calculates ejection force.
2. annan claims it exceeds retention force.
3. annan claims the sky is falling and threatens lawsuits.
4. annan refuses to calculate retention force.
5. i estimate retention force based on material deformation and derive a
number that exceeds ejection force many times.
6. riel refines that calculation and it still exceeds ejection force
many times.
7. in an effort to "prove" that wheels are ejected, we then observe
attempts to "up" the annan ejection force by claiming some sort of
transient, unmeasured, unobserved deceleration which might help fudge
the figures.
8. wheels still don't fall out.
9. the faithful weep and gnash their teeth.

At that time you just disappeared out of the subsequent
conversation.

so sorry. some of us work for a living. occasionally. forgive my
sadly misdirected priorities.


And as you neglect to note, actual ejections have been reported.

globally, we can still count them on the fingers of one hand can't we?
what's that in terms of percentage of disk brakes deployed? how does it
compare to fork crown failure rates? brake lever failure rates?
handlebar failure rates? sticks getting stuck in spokes and o.t.b.'ing
the rider failure rates? and aren't all those "ejections" involving
custom forks without lawyer lips? and even more important than all
that, are we able to eliminate operator error and definitively /prove/
it's an indisputable design flaw? be careful there tim - things like
wheels fall off cars all the time when lug nuts aren't tightened
properly, and people get hurt. that's not a design flaw.

In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

it's just legal ambulance chasing by those who aren't analyzing the
full picture. yes, disks cause a resolved force in the direction of
the open end of a dropout. but since this force is exceeded 3 or
more times by the retaining force of a properly tightened skewer,
it's an argument without merit. as evidence by the lack of actual
ejections.

You were shown the math a couple of years ago that clearly showed that
the ejection force could readily exceed the retention force at realistic
decelerations.

that's strange. i recall it like this:

Your memory is faulty.

1. annan calculates ejection force.
2. annan claims it exceeds retention force.
3. annan claims the sky is falling and threatens lawsuits.
4. annan refuses to calculate retention force.

I did the calculations to which I refer, which showed that the ejection
force could readily exceed the requirements established by the CPSC for
retention force. The calculations were corrected by another poster to
show that I had underestimated the magnitude by which the ejection force
exceeded the required retention force.

5. i estimate retention force based on material deformation and derive a
number that exceeds ejection force many times.

At this point the saving grace is the interlock between the serrations
of the skewer and locknut and the softer metal of the dropouts. But
it's a thin margin that leaves too little room for error.

You continue to ignore the simple fact that the existence of the
ejection force *is* the design flaw. I strongly suspect that if Jobst
had come out critical of Annan's analysis, you'd have defended Annan.

6. riel refines that calculation and it still exceeds ejection force
many times.
7. in an effort to "prove" that wheels are ejected, we then observe
attempts to "up" the annan ejection force by claiming some sort of
transient, unmeasured, unobserved deceleration which might help fudge
the figures.
8. wheels still don't fall out.
9. the faithful weep and gnash their teeth.

You overestimate the devastating effect of your argumentation.

On Wed, 07 Feb 2007 20:28:02 -0600, Tim McNamara
wrote:

In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

it's just legal ambulance chasing by those who aren't analyzing the
full picture. yes, disks cause a resolved force in the direction of
the open end of a dropout. but since this force is exceeded 3 or
more times by the retaining force of a properly tightened skewer,
it's an argument without merit. as evidence by the lack of actual
ejections.

You were shown the math a couple of years ago that clearly showed that
the ejection force could readily exceed the retention force at realistic
decelerations.

that's strange. i recall it like this:

Your memory is faulty.

1. annan calculates ejection force.
2. annan claims it exceeds retention force.
3. annan claims the sky is falling and threatens lawsuits.
4. annan refuses to calculate retention force.

I did the calculations to which I refer, which showed that the ejection
force could readily exceed the requirements established by the CPSC for
retention force. The calculations were corrected by another poster to
show that I had underestimated the magnitude by which the ejection force
exceeded the required retention force.

5. i estimate retention force based on material deformation and derive a
number that exceeds ejection force many times.

At this point the saving grace is the interlock between the serrations
of the skewer and locknut and the softer metal of the dropouts. But
it's a thin margin that leaves too little room for error.

You continue to ignore the simple fact that the existence of the
ejection force *is* the design flaw. I strongly suspect that if Jobst
had come out critical of Annan's analysis, you'd have defended Annan.

6. riel refines that calculation and it still exceeds ejection force
many times.
7. in an effort to "prove" that wheels are ejected, we then observe
attempts to "up" the annan ejection force by claiming some sort of
transient, unmeasured, unobserved deceleration which might help fudge
the figures.
8. wheels still don't fall out.
9. the faithful weep and gnash their teeth.

You overestimate the devastating effect of your argumentation.

Dear Tim,

Calculation arguments aside, do you know if anyone has ever reproduced
the claimed phenomenon?

That is, are there any experiments that confirm or refute claims that
a bicycle wheel with a reasonably tightened quick-release can be
ejected by disk-brake brake forces before the tire skids?

Cheers,

Carl Fogel

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

it's just legal ambulance chasing by those who aren't analyzing the
full picture. yes, disks cause a resolved force in the direction of
the open end of a dropout. but since this force is exceeded 3 or
more times by the retaining force of a properly tightened skewer,
it's an argument without merit. as evidence by the lack of actual
ejections.
You were shown the math a couple of years ago that clearly showed that
the ejection force could readily exceed the retention force at realistic
decelerations.
that's strange. i recall it like this:

Your memory is faulty.

1. annan calculates ejection force.
2. annan claims it exceeds retention force.
3. annan claims the sky is falling and threatens lawsuits.
4. annan refuses to calculate retention force.

I did the calculations to which I refer, which showed that the ejection
force could readily exceed the requirements established by the CPSC for
retention force.

that's the logical disconnect and the fundamental flaw to annan's theory
- cpsc numbers are not real for serrated axle faces biting alloy fork ends.

The calculations were corrected by another poster to
show that I had underestimated the magnitude by which the ejection force
exceeded the required retention force.

"required"? it needs to exceed /actual/ retention force. and this is
why we don't have ejections in the real world.


5. i estimate retention force based on material deformation and derive a
number that exceeds ejection force many times.

At this point the saving grace is the interlock between the serrations
of the skewer and locknut and the softer metal of the dropouts. But
it's a thin margin that leaves too little room for error.

You continue to ignore the simple fact that the existence of the
ejection force *is* the design flaw.

no it's not - we've had this discussion before. there's a force that is
constantly trying to break your fork crown, fatigue your brake cables,
snap your pedal spindles, etc., etc. it's all a question of whether
load exceeds strength. if it doesn't, it won't. real basic.

in this case, annan had to fish around for numbers that his calculated
ejection force would exceed. he did not, and still will not, calculate
actual retention force. your dismissal of this situation with "little
room for error" is ridiculous since retention force exceeds ejection
force by at least 3 times. how much "room for error" does your fork
crown have?

I strongly suspect that if Jobst
had come out critical of Annan's analysis, you'd have defended Annan.

no, i'll give credit where due. in this instance, jobst, just like most
others, got suckered in by annan quietly avoiding reality of lawyer lips
and serrated axle faces creating /much/ higher retention forces than
suited his desire for sensationalism. you can't just calculate one side
of the equation then ignore the other because it doesn't suit. i don't
care /who/ makes that mistake.


6. riel refines that calculation and it still exceeds ejection force
many times.
7. in an effort to "prove" that wheels are ejected, we then observe
attempts to "up" the annan ejection force by claiming some sort of
transient, unmeasured, unobserved deceleration which might help fudge
the figures.
8. wheels still don't fall out.
9. the faithful weep and gnash their teeth.

You overestimate the devastating effect of your argumentation.

why did you snip my questions about failure rates? i mean it seriously
- globally, how many ejections have there been? aren't they all from
custom forks without lawyer lips? and how can we definitely disprove
user error?

wrote in message
news
On Wed, 07 Feb 2007 20:28:02 -0600, Tim McNamara
wrote:

In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

it's just legal ambulance chasing by those who aren't analyzing the
full picture. yes, disks cause a resolved force in the direction of
the open end of a dropout. but since this force is exceeded 3 or
more times by the retaining force of a properly tightened skewer,
it's an argument without merit. as evidence by the lack of actual
ejections.

You were shown the math a couple of years ago that clearly showed that
the ejection force could readily exceed the retention force at
realistic
decelerations.

that's strange. i recall it like this:

Your memory is faulty.

1. annan calculates ejection force.
2. annan claims it exceeds retention force.
3. annan claims the sky is falling and threatens lawsuits.
4. annan refuses to calculate retention force.

I did the calculations to which I refer, which showed that the ejection
force could readily exceed the requirements established by the CPSC for
retention force. The calculations were corrected by another poster to
show that I had underestimated the magnitude by which the ejection force
exceeded the required retention force.

5. i estimate retention force based on material deformation and derive a
number that exceeds ejection force many times.

At this point the saving grace is the interlock between the serrations
of the skewer and locknut and the softer metal of the dropouts. But
it's a thin margin that leaves too little room for error.

You continue to ignore the simple fact that the existence of the
ejection force *is* the design flaw. I strongly suspect that if Jobst
had come out critical of Annan's analysis, you'd have defended Annan.

6. riel refines that calculation and it still exceeds ejection force
many times.
7. in an effort to "prove" that wheels are ejected, we then observe
attempts to "up" the annan ejection force by claiming some sort of
transient, unmeasured, unobserved deceleration which might help fudge
the figures.
8. wheels still don't fall out.
9. the faithful weep and gnash their teeth.

You overestimate the devastating effect of your argumentation.

Dear Tim,

Calculation arguments aside, do you know if anyone has ever reproduced
the claimed phenomenon?

That is, are there any experiments that confirm or refute claims that
a bicycle wheel with a reasonably tightened quick-release can be
ejected by disk-brake brake forces before the tire skids?

Cheers,

Carl Fogel

Carl,
I'd love to see photos of the experiment you devise to test this one!
A little more seriously, I read some of the stuff on the web about this - my
impression is that, _if_ there is a problem, it is caused by the nut
unscrewing from the skewer. A fix might be a quick release nut with a tab
that fits in the slot in the fork end. When adjusting the tightness of the
quick release, rotate the nut as far counter clock wise as possible (the tab
touching the inside of the slot in the fork end). Then, after the quick
release is clamped shut, the nut won't be able to loosen. The quick release
lever might end up in some unaesthetic orientation, though.
Kerry (who has never ridden a bike with disk brakes)

Tim McNamara wrote:
In article ,
jim beam wrote:
Tim McNamara wrote:
In article ,
jim beam wrote:
-disc Q/R wheels eject on braking-
-does not / does too-
-repeat-

jim beam wrote:
i mean it seriously
- globally, how many ejections have there been? aren't they all from
custom forks without lawyer lips? and how can we definitely disprove
user error?

That's the compelling argument for me..

Now that millions of XMart bikes equipped with disc brakes, sloppy
assembly, inattentive owners and CPSC quick releases have been on the
road a few years, we'd expect more than a couple of anecdotal incidents
if the situation were truly dire.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

On Wed, 07 Feb 2007 00:49:23 -0700, may have
said:

On Wed, 07 Feb 2007 03:27:21 GMT, Martin Dann
wrote:

Mike Causer wrote:
On Tue, 06 Feb 2007 18:40:59 +0000, wafflycat wrote:

http://www.bikebiz.com/Wheel-ejection-theory-goes-legal

Ummmmm. So who's going to announce this on r.b.t?


Mike

Dear Mike, Martin, & WC,

Should we expect to see the theory confirmed by reproduction? Or has
that already been done?

This is just blatant speculation, but I look for the eventual finding
to be that the design has a problem which can result in wheel ejection
which would not occur with a rim-brake bike, due to a marginal
operational condition that poses a special hazard which is easily
overlooked and can go unrecognized even with casual inspection due to
a lack of other symptoms.

Mitigating in favor of the defense is the relatively small number of
recorded incidents; it may be difficult to convince a court that the
problem is as fraught with peril as has been claimed by some, when the
vast majority of bikes under discussion do not show any signs of the
failure. The manufacturers might actually be better off if they can
demonstrate a repeatable and applicable failure mode to explain the
incident under review, particularly if the failure requires a special
set of circumstances before it will actually manifest itself. This
would, at least, allow a reasonable quantification of the risk for the
average rider, which would in turn permit the legal types to assess
what the liability should be.

Of course, nearly any such finding could cause some relatively massive
disruptions in the manufacturing and distribution areas, with the
possibility that some distributors for foreign manufacturers might be
bankrupted if large numbers of forks end up having to be replaced.
(This would not be the first time that such a result had been seen.)
What I more strongly suspect is that a whole lot of QR axles could end
up recalled for replacement by solids, or perhaps an anti-ejection
clip of some sort may be introduced to band-aid over the problem. In
the main, I doubt that the final result will be as drastic as the
worst-case scenarios paint it, for a variety of practical reasons.

--
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Words processed in a facility that contains nuts.