CPSC judgement on disk brakes and QR forks

[Jay Beattie]

"gwhite" <[email protected]> wrote in message news:[email protected]...
>
>
> "S. Anderson" wrote:
> >
> > <[email protected]> wrote in message
> > news:[email protected]...
> > >
> > > What strike me about this is that it is a typical NASA "culture" approach to the subject. If
> > > you read the item on NASA denial at:
> > >
> > >
> >
http://www.sfgate.com/cgi-bin/article.cgi?file=/news/archive/2003/08/26/ nati
> > onal0151EDT0426.DTL
> > >
> > > You could easily replace NASA with CPSA and the glove would fit.
> > >
> > > I see we must wait for one of the victims to bring a multi-million
$
> > > damage claim against the industry. CPSA should be culpable as
well.
> > >
> > > Jobst Brandt [email protected] Palo Alto CA
> >
> > I think NASA is its own little universe. I'm not sure that the
situation
> > that exists there, an organization that is dependent on government
funding
> > for its existence, can necessarily be translated to this situation.
But to
> > be sure, most large corporations behave in a similar fashion to the
CPSA in
> > this case. Certainly the auto industry does. It will boil down to
the
> > cheaper option: lawsuits or revising the product to make it safe.
As far as
> > most corporations go, a human life has a price. And if that price
is lower
> > than fixing the problem, the problem usually doesn't get fixed. Sad
as that
> > may be.

I met Hal Stratton, the Chairman of the CPSC, a few months ago. I was prepared to hate him because
he is a Bush appointee, but he seemed like a nice guy who takes his job very seriously. But his job
is a big one, and the CPSC has a tiny budget. In fact, there should be five commissioners, but only
three spots have been funded. It is not a billion dollar agency like NASA. I does not own real
estate in Florida or employ rocket scientists or maintain spaceships. Hal has a lot to worry about
besides after market bicycle brakes -- like things that blow up and catch on fire and really hurt
people besides Missy Giove.

> Hey, if tort law "reform" passes, even the civil court route might fail. Caveat emptor.

Class action and tort reform is needed, and the reform I have seen proposed would not prevent most
products-related law suits. It usually involves damages caps and exclusive federal jurisdiction over
certain suits, and most proposed reform at the local level involves doctors who have been sued out
of delivering babies. It will never pass anyway, because the trial lawyers have more money than
industry -- plus they get Erin Brockovich to display her breasts and talk about the importance of
the jury system -- when her famous case was decided by an arbitrator (go figure). -- Jay Beattie.

 

[S. Anderson]

"Jay Beattie" <[email protected]> wrote in message news:[email protected]...
>
>
> > Hey, if tort law "reform" passes, even the civil court route might fail. Caveat emptor.
>
> Class action and tort reform is needed, and the reform I have seen proposed would not prevent most
> products-related law suits. It usually involves damages caps and exclusive federal jurisdiction
> over certain suits, and most proposed reform at the local level involves doctors who have been
> sued out of delivering babies. It will never pass anyway, because the trial lawyers have more
> money than industry -- plus they get Erin Brockovich to display her breasts and talk about the
> importance of the jury system -- when her famous case was decided by an arbitrator (go figure). --
> Jay Beattie.
>
>

Interesting. I think it's commonly thought up here (Canada) that the civil legal system is out of
control in the States. We often read things about auto lawsuits (I'm in the engineering business)
and wonder which way is up. You know, the usual millions awarded some drunk driver who fell asleep
at the wheel at 140mph and crashed into a bridge abutment whose family argues that the car should
have protected the driver against all foreseeable impacts, or someone with a "back injury" who sues
for salary and the right to never work again due to this injury etc etc. Is that the common thought
in the States as well? Is this the motivation for the civil litigation reform?

Incidentally, I really enjoyed Dr. Feynman's article on the first shuttle crash. He asked the
engineers on the floor what their estimate of total vehicle loss on any given mission was, approx. 1
in 50 or 1 in 100. He THEN asked NASA management, who confidently assured him the chances were more
like 1 in 100,000. It seems the same problems illustrated 15 years ago reveal themselves again.

Cheers,

Scott..

 

[Mike S.]

<[email protected]> wrote in message news:[email protected]...
> Mike Shaw writes:
>
> >> If no one knew about it, what would prompt someone to do something?
>
> > If noone knows, is there a really a problem?
>
> Noon is the time we usually eat lunch, no one should have a problem with that...
>

Well, since Miraim-Webster puts a space in, from now on so will I.

> However, causes for all sorts of common phenomena are being discovered daily. That wheels have
> separated is not a contention here but what one of the causes are is.
>

A small correction of terminology: a potential cause.

> > Seems that someone would know if they had a problem with their dropouts, and the LBS would start
> > to hear about it, and then the manufacturers would start to get warranty claims, and...
>
> Oh, what you say. We read here regularly of people who have common mechanical problems with their
> bicycles and are at a loss to explain what the cause is. Likewise, those who have had a wheel come
> out are no better informed, especially since attributing it to incorrect QR closure is simple and
> entirely believable. For proof of that, just read the insulting responses James Annan has gotten
> from this forum.
>
> > Sounds to me like some little boy's calling "wolf."
>
> Mike, what motivates you to take this position?
Why do you feel so attacked that you must go on the offensive and give rude retorts to someone who
has done nothing to you?
>
Now THAT'S the pot calling the kettle black! At least in this post you're being polite, thank you.
To answer, I don't feel like I'm being attacked, I just feel that there are people out there trying
to create a problem where there really isn't one.

That there are wheels being ejected for some reason is a given. We've got actual examples. To blame
everything BUT user error sounds like someone's crying wolf. If there is a real problem, AND it can
be definitively proven to be the QR/dropout design, I'll be the first to change my opinion. Right
now, I haven't seen anything to definitely PROVE that it's the QR.

Personal experience, the personal experience of everyone I know, and everyone they know (and a lot
work in shops) hasn't come up with one example of this phenomenon in the SoCal/San Diego area that
I've heard of. Have you heard of anyone that has had the problem? Seems to me that if there were
actually a problem, at least one of us would've heard about it by now.

Mike

> Jobst Brandt [email protected] Palo Alto CA

 

[Super Slinky]

Mike S. said...

> Now THAT'S the pot calling the kettle black! At least in this post you're being polite, thank you.
> To answer, I don't feel like I'm being attacked, I just feel that there are people out there
> trying to create a problem where there really isn't one.
>
> That there are wheels being ejected for some reason is a given. We've got actual examples. To
> blame everything BUT user error sounds like someone's crying wolf. If there is a real problem, AND
> it can be definitively proven to be the QR/dropout design, I'll be the first to change my opinion.
> Right now, I haven't seen anything to definitely PROVE that it's the QR.
>
> Personal experience, the personal experience of everyone I know, and everyone they know (and a lot
> work in shops) hasn't come up with one example of this phenomenon in the SoCal/San Diego area that
> I've heard of. Have you heard of anyone that has had the problem? Seems to me that if there were
> actually a problem, at least one of us would've heard about it by now.
>
> Mike

The only place I have heard about unexplained wheel ejection is in these usenet threads. This isn't
to say that it never happens, it just isn't that common compared to the usual mechanical failures
like bent rims, and broken frames. As off-road bicyclists we just have more important things to
worry about. I was always willing to admit that James Annan had an interesting point, but it was the
hype, the ego and the exaggeration that made me want to jump in and throw some obstacles in front of
the band wagon, for whatever good it did. Less scare-mongering and arrogance might have actually
resulted in a better reception by the world cycling community. Instead we get a guy trying to set
himself up as the Ralph Nader of bicycles. How could any rational person not give a resounding Bronx
cheer to that? Fortunately, the bicycling community is smaller and more sophisticated than the auto
industry and that turkey won't fly in this little world.

 

[Doug Taylor]

Tim McNamara <[email protected]> wrote:

>> The CPSC is supposed to be above politics
>
>The CPSC on which planet? The one in the US is terminally embroiled in politics, and those politics
>change like the wind with the various Administrations. This Administration is determined to remove
>as much government interference from business as possible (while maximizing big government
>interference into people's personal lives). You can be sure that the CPSC will be rendered as
>powerless as possible for the next 6 years.

I get it. It's a conspiracy! The government wants to hide this huge problem with disc brakes and
quick releases, which is a dire threat to the health and freedom of all cyclists, so that Big
Business (the bike industry? Hah) will thrive. But little Timmie McNamara knows the TRUTH. He heard
it from James Annan, who crashed on his tandem, and Jobst Brandt, who knows everything. So it must
be true. Forget the fact that if it were true, it would be in the interest of the CPSC and the
cycling industry to nip it in the bud, BEFORE the tort lawyers blow the whole thing to holy hell.
And that only a tiny minority of cyclists have been injured by this problem, IF it's a problem and
IF the problem caused the injury. --dt

 

[Joe Riel]

"Mike S." <mikeshaw2@coxDOTnet> writes:

> That there are wheels being ejected for some reason is a given. We've got actual examples. To
> blame everything BUT user error sounds like someone's crying wolf.

"To blame *everything* but user error"? James is putting the blame on precisely one thing. It is
those who do not understand engineering mechanics that are missing the point.

> Personal experience, the personal experience of everyone I know, and everyone they know (and a lot
> work in shops) hasn't come up with one example of this phenomenon in the SoCal/San Diego area that
> I've heard of.

Lots of products have been recalled, how much personal experience do you have with people being
injured as a result of a defective design that was recalled? I cannot think of anyone. Presumably
the CPSC doesn't rely on personal experience when making a judgement. Are recalls unjustified unless
most people have personal experience with that product failure [rhetorical question]?

Joe Riel

 

[Jay Beattie]

"S. Anderson" <[email protected]> wrote in message
news:T%[email protected]...
> "Jay Beattie" <[email protected]> wrote in message
> news:[email protected]...
> >
> >
> > > Hey, if tort law "reform" passes, even the civil court route might fail. Caveat emptor.
> >
> > Class action and tort reform is needed, and the reform I have seen proposed would not prevent
> > most products-related law suits. It
usually
> > involves damages caps and exclusive federal jurisdiction over
certain
> > suits, and most proposed reform at the local level involves doctors
who
> > have been sued out of delivering babies. It will never pass anyway, because the trial lawyers
> > have more money than industry -- plus they
get
> > Erin Brockovich to display her breasts and talk about the importance
of
> > the jury system -- when her famous case was decided by an arbitrator
(go
> > figure). -- Jay Beattie.
> >
> >
>
> Interesting. I think it's commonly thought up here (Canada) that the
civil
> legal system is out of control in the States. We often read things
about
> auto lawsuits (I'm in the engineering business) and wonder which way
is up.
> You know, the usual millions awarded some drunk driver who fell asleep
at
> the wheel at 140mph and crashed into a bridge abutment whose family
argues
> that the car should have protected the driver against all foreseeable impacts, or someone with a
> "back injury" who sues for salary and the
right
> to never work again due to this injury etc etc. Is that the common
thought
> in the States as well? Is this the motivation for the civil
litigation
> reform?

The too big verdict is one of the motivating factors for tort reform, but the more important problem
is the effect of mass tort litigation on certain legitimate industries, and the abuse of the class
action procedure. Random bad verdicts will always occur, but there are system problems that could be
fixed without denying reasonable compensation to legitimately injured plaintiffs. It has been done
in Canada and elsewhere in the civilized world. -- Jay Beattie.

 

[Spider]

"Mike S." <mikeshaw2@coxDOTnet> wrote in message news:<dTB3b.30101$cj1.11404@fed1read06>...
> <[email protected]> wrote in message
> news:[email protected]...

> > However, causes for all sorts of common phenomena are being discovered daily. That wheels have
> > separated is not a contention here but what one of the causes are is.
> >
>
> A small correction of terminology: a potential cause.
> >
> > > Sounds to me like some little boy's calling "wolf."
> >
> > Mike, what motivates you to take this position? Why do you feel so attacked that you must go on
> > the offensive and give rude retorts to someone who has done nothing to you?
> >
>
> Now THAT'S the pot calling the kettle black! At least in this post you're being polite, thank you.
> To answer, I don't feel like I'm being attacked, I just feel that there are people out there
> trying to create a problem where there really isn't one.

Or that the problem has not been clearly defined in it's actual failure mode.

> That there are wheels being ejected for some reason is a given. We've got actual examples. To
> blame everything BUT user error sounds like someone's crying wolf. If there is a real problem, AND
> it can be definitively proven to be the QR/dropout design, I'll be the first to change my opinion.
> Right now, I haven't seen anything to definitely PROVE that it's the QR.

That's not entirely accurate. At this point, it is really unknown what the "user error" failure rate
is, in comparison to the proposed mechanism.

> Personal experience, the personal experience of everyone I know, and everyone they know (and a lot
> work in shops) hasn't come up with one example of this phenomenon in the SoCal/San Diego area that
> I've heard of. Have you heard of anyone that has had the problem? Seems to me that if there were
> actually a problem, at least one of us would've heard about it by now.

Mr. Annan seems to think his anecdotes are golden, while everyone else's anecdotes are a little more
"brown", if you get my meaning.

Ms. Macnamara (sorry about the spelling if it is not correct) Mr. Brandt and Mr Annan, plus some few
others, consider this hypothesis as reality, and that it's fixed in stone that "this is what
happens." But they seem to blanch at responding to these questions:

What is the ratio of user error failures to Annan Hypothesis failures?

What is the effect of knurling on the QR and hub nut faces? (The unscrewing mechanism is an analogy
to vibrational loosening which is well-documented, EXCEPT - when was the last time you saw a screw
with a knurled mating face? A bolt? A nut? A washer, other than lockwashers, which are "knurled" for
a reason!) As the unscrewing mechanism applies to *this particular application*, under what
conditions does it happen with the QR done up *as the manufacturer recommends*? How about when it's
tighter than that?

How was the 0.6g decelleration figure arrived at? (This is one I've had a problem with from the
beginning - I don't know where to get a g-meter for my mtb. I would be willing to experiment if
I had one.)

Why is only the rotor side considered in the calculation? The fork ends are not free-floating,
frictionless, independent entities.

I have seen a bunch of hand waving at these questions, like they don't matter. And I have seen
condescending remarks thrown around about "look it up." And yet, when I go and "look it up," I
see nothing but more hand-waving! Mr. Brandt's claim of the existance of statistics. That one was
a laugher.

The fact is, I want to know specifics, and not hear "any mechanical engineer would know that this
is" thus and such. OK, I'm not one. Convince me that this a real threat, and not a potential threat.
There are real threats out there - like every time I drive an automobile, there is a real and
quantifiable threat of injury and death. Likewise just about every other activity. And there are
things that I can do to mitigate the potential threats.

Here are the things I see:

Downward force on the drop-out - bad. Moving the disk mounts to the other side, and in front of the
fork would solve that problem with no changes to the rest of the system.

Potential unscrewing of the QR - bad. Without this part of the equation, the downward force is
merely a result of design compromise. This is the area that I see needs to be elucidated more - what
is the threshold tension, what effect does knurling have, how do those two things interact, etc.

Actual force on the dropout from braking - number of unknown value. .6g is pretty high for a mtb on
dirt. I'm not sure how often I get to 0.6g on pavement, let alone dirt. Knobbies are not well-suited
to pavement, so it's hard to judge. From my time spent running around a track in my car, I rarely
see 0.6g on the street (driving in a regular fashion.) On the track, quite often, and by estimate of
what my body feels when I'm on dirt, 0.6g doesn't happen a lot. If at all. I need a g-meter to test
this. This is the one number that I feel has been "pulled out of the air."

I wouldn't have any problem with the discussion at all - except that the aforementioned proponents
of the Annan Hypothesis seem to think that dimissive condescension makes these questions up and
disappear. They do not. In fact, the handwaving strengthen these questions, and make me wonder what
the real motivation is. If they'd drop the pretense of "knowing", and approach it more as "answering
the questions posed in a straight-forward manner", then I might be more inclined to spend my time
writing to, oh, the CPSC! Or Marzocchi. As it is, I am sitting with figurative arms crossed, waiting
for more definitive answers, including the German experiments mentioned previously.

Robert F. Jones (Spider, to the rest of USENET)

 

[Jobst Brandt]

Mike Shaw writes:

>> Mike, what motivates you to take this position? Why do you feel so attacked that you must go on
>> the offensive and give rude retorts to someone who has done nothing to you?

> Now THAT'S the pot calling the kettle black! At least in this post you're being polite, thank you.
> To answer, I don't feel like I'm being attacked, I just feel that there are people out there
> trying to create a problem where there really isn't one.

> That there are wheels being ejected for some reason is a given. We've got actual examples. To
> blame everything BUT user error sounds like someone's crying wolf. If there is a real problem, AND
> it can be definitively proven to be the QR/dropout design, I'll be the first to change my opinion.
> Right now, I haven't seen anything to definitely PROVE that it's the QR.

> Personal experience, the personal experience of everyone I know, and everyone they know (and a lot
> work in shops) hasn't come up with one example of this phenomenon in the SoCal/San Diego area that
> I've heard of. Have you heard of anyone that has had the problem? Seems to me that if there were
> actually a problem, at least one of us would've heard about it by now.

OK. How about a simple experiment, assuming you have access to a disk brake equipped bicycle. Since
retention ridges are only on the outside of the fork dropout, remove the QR skewer and perform a
static braking test by pushing the bicycle forward with the brake applied. You could also do this at
low speed without hazard. Then report whether this disengages the wheel or not.

This is intended to demonstrate that there is a separating force, something that has been argued
here at length.

Jobst Brandt [email protected] Palo Alto CA

 

[Mike S.]

<[email protected]> wrote in message news:[email protected]...
> Mike Shaw writes:
>
> >> Mike, what motivates you to take this position? Why do you feel so attacked that you must go on
> >> the offensive and give rude retorts to someone who has done nothing to you?
>
> > Now THAT'S the pot calling the kettle black! At least in this post you're being polite, thank
> > you. To answer, I don't feel like I'm being attacked, I just feel that there are people out
> > there trying to create a problem where there really isn't one.
>
> > That there are wheels being ejected for some reason is a given. We've got actual examples. To
> > blame everything BUT user error sounds like someone's crying wolf. If there is a real problem,
> > AND it can be definitively proven to be the QR/dropout design, I'll be the first to change my
> > opinion. Right now, I haven't seen anything to definitely PROVE that it's the QR.
>
> > Personal experience, the personal experience of everyone I know, and everyone they know (and a
> > lot work in shops) hasn't come up with one example of this phenomenon in the SoCal/San Diego
> > area that I've heard of. Have you heard of anyone that has had the problem? Seems to me that if
> > there were actually a problem, at least one of us would've heard about it by now.
>
> OK. How about a simple experiment, assuming you have access to a disk brake equipped bicycle.
> Since retention ridges are only on the outside of the fork dropout, remove the QR skewer and
> perform a static braking test by pushing the bicycle forward with the brake applied. You could
> also do this at low speed without hazard. Then report whether this disengages the wheel or not.
>
> This is intended to demonstrate that there is a separating force, something that has been argued
> here at length.

Yeah, and I'll bet that if you did the same with cantis or V-brakes, it'd do the same thing. Since I
haven't tried it, I don't know. Anyone willing to try?

I've got an F3000 out in the garage that I can experiment with in a bit. I'll let you know
what happens.

Mike

>
> Jobst Brandt [email protected] Palo Alto CA

 

[Mike S.]

"David Damerell" <[email protected]> wrote in message
news:CfD*[email protected]...
> Spider <[email protected]> wrote:
> >How was the 0.6g decelleration figure arrived at? (This is one I've had a problem with from the
> >beginning - I don't know where to get a g-meter for my mtb. I would be willing to experiment if I
> >had one.)
>
> As was explained to you at the time, the maximum deceleration attainable without lifting the rear
> wheel on the flat is directly determined by the angle between the horizontal and a line drawn
> through the forward contact patch and the centre of gravity of the bike+rider.
> --
> David Damerell <[email protected]> Kill the tomato!

Is that assuming that you don't shift your weight to the rear: sitting on the saddle? or is it
measured when your butt is behind the saddle, arms extended? Inquiring minds want to know...

Mike

 

[Tim McNamara]

In article <[email protected]>, Super Slinky
<[email protected]> wrote:

> I was always willing to admit that James Annan had an interesting point, but it was the hype, the
> ego and the exaggeration that made me want to jump in and throw some obstacles in front of the
> band wagon, for whatever good it did.

No good at all, in fact attitudes like yours do harm instead.

It's very odd, unlike you and several others I saw no ego or hype or exaggeration in Annan's posts.
I initially disagreed with him- indeed, I was the first responder and told him his idea was all wet-
believing like many that all failures of the QR to hold the wheel in the dropout are the result of
user error. After all, that's what "everyone knows" is the case with QRs.

However, the situation with disk brake forks is different than the situation with other types of
wheels, in that the brake puts an ejection force on the wheel that is absent in all other designs.
That this force is asymmetrical adds another dimension to the problem, and that the force occurs in
suspension forks that have a degree of independence between the movement of the two legs further
adds to the problem.

> Less scare-mongering and arrogance might have actually resulted in a better reception by the world
> cycling community. Instead we get a guy trying to set himself up as the Ralph Nader of bicycles.
> How could any rational person not give a resounding Bronx cheer to that?

Oh ********. This is a problem of your interpretation, not a problem with what Annan published here
and on his Web site. The rational response would have been to examine the analysis and the available
evidence, which in turn would have brought you to the conclusion that Annan has a valid point.
Further independent testing and examination has verified- in a preliminary fashion at least- both
the ejection force and the loosening of QRs.

> Fortunately, the bicycling community is smaller and more sophisticated than the auto industry and
> that turkey won't fly in this little world.

Only if you think that being hidebound and superstitious are the same as being "more sophisticated."
Because that's the situation with bicyclists- we have an extensive lore based on little more than
supersition and mistaken attribution. The turkey files just fine in this little world, but few will
open their eyes to see the fact.

 

[Tim McNamara]

In article <[email protected]>, Doug Taylor
<[email protected]> wrote:

> I get it. It's a conspiracy! The government wants to hide this huge problem with disc brakes and
> quick releases, which is a dire threat to the health and freedom of all cyclists, so that Big
> Business (the bike industry? Hah) will thrive. But little Timmie McNamara knows the TRUTH. He
> heard it from James Annan, who crashed on his tandem, and Jobst Brandt, who knows everything. So
> it must be true. Forget the fact that if it were true, it would be in the interest of the CPSC and
> the cycling industry to nip it in the bud, BEFORE the tort lawyers blow the whole thing to holy
> hell. And that only a tiny minority of cyclists have been injured by this problem, IF it's a
> problem and IF the problem caused the injury. --dt

Ah, Dougie, you've been listening to too much Rush again. These paranoid theories of yours- and
Rush's as well- are treatable, after all. Consider looking into it. ;-)

 

[Tim McNamara]

In article <PrL3b.32217$cj1.11028@fed1read06>, "Mike S." <mikeshaw2@coxDOTnet> wrote:

> <[email protected]> wrote in message
> news:[email protected]...
>
> > OK. How about a simple experiment, assuming you have access to a disk brake equipped bicycle.
> > Since retention ridges are only on the outside of the fork dropout, remove the QR skewer and
> > perform a static braking test by pushing the bicycle forward with the brake applied. You could
> > also do this at low speed without hazard. Then report whether this disengages the wheel or not.
> >
> > This is intended to demonstrate that there is a separating force, something that has been argued
> > here at length.
>
> Yeah, and I'll bet that if you did the same with cantis or V-brakes, it'd do the same thing. Since
> I haven't tried it, I don't know. Anyone willing to try?

Umm, it's been done. It's been written up in this newsgroup.

> I've got an F3000 out in the garage that I can experiment with in a bit. I'll let you know what
> happens.

Please do. Having checked this out personally, I can tell you what you will find. The wheel will
stay in the dropouts with caliper brakes, cantilever brakes and V brakes. The wheel will be pushed
out of the dropout with disk brakes.

That there is a ejection force created by disk brakes is not in dispute, although you seem to
continue to think that it is. This has been verified by informal testing by participants in this
newsgroup, and has been verified by independent testing within the bike industry. The reference for
this has been posted several times, and it is entertaining to note that Annan's critics continue to
be silent about this.

The alleged hype and ego are now on the side of the people trying to argue against observable
reality. At this point in the discussion, sheer obstructionism or lack of simple comprehension seem
to be the only explanations.

 

[Mike S.]

. Further independent testing and examination
> has verified- in a preliminary fashion at least- both the ejection force and the loosening of QRs.
>
When was the last time a QR came undone spontaneously? Snagged on trees, bushes, bashed on rocks,
yes. Loosen completely on its own? Hmmm... don't think so.

I just did the test that Jobst recommended and indeed, my disc equipped wheel migrated back and down
when there was no clamping pressure applied by the QR. However, once there was pressure applied by
the QR, this tendency was overcome.

The only way I can see my front wheel ejecting itself spontaneously from my forks is if the QR is
either installed incorrectly, breaks, or there's a massive side load that pulls the wheel partially
out of the dropout first. In the first instance, it is still user error. The second is equipment
failure which would be possible to be caught in time with proper maintenance. The third would
probably mean that you have to stop riding and fix your wheel before continuing, allowing you to
tighten an otherwise loose QR.

I can see how using Ti QRs would be asking for trouble when running discs. I can also see that
filing off the "lawyer lips" on a disc brake equipped bike is not a good thing either, if just for
the additional insurance "just in case."

I can also see why I wouldn't want my disc caliper on the front of my fork. That much delicate stuff
right in the way of trees, rocks, etc. What the "answer" is, I haven't a clue.

Questions that just popped into my mind: Exactly how much force does it take to eject the wheel from
a properly tightened QR/fork interface? How much force is a "typical" QR exerting? Exactly where is
the tendency of the wheel to come out of the bottom of the fork equal to the clamping force of the
QR? How much force is the disc brake exerting on the QR/fork interface? How deep would a dropout
have to be to keep a wheel in the fork? Maybe a "J" shaped dropout would work?

Mike

 

[Mike S.]

> > I've got an F3000 out in the garage that I can experiment with in a bit. I'll let you know what
> > happens.
>
> Please do. Having checked this out personally, I can tell you what you will find. The wheel will
> stay in the dropouts with caliper brakes, cantilever brakes and V brakes. The wheel will be pushed
> out of the dropout with disk brakes.
>
> That there is a ejection force created by disk brakes is not in dispute, although you seem to
> continue to think that it is. This has been verified by informal testing by participants in this
> newsgroup, and has been verified by independent testing within the bike industry. The reference
> for this has been posted several times, and it is entertaining to note that Annan's critics
> continue to be silent about this.
>
> The alleged hype and ego are now on the side of the people trying to argue against observable
> reality. At this point in the discussion, sheer obstructionism or lack of simple comprehension
> seem to be the only explanations.

I have never argued that there ISN'T a force ejecting the wheel. Just that there has to be something
else going on to make a wheel spontaneously jump out of a perfectly good dropout.

There I was, JRA, when BAM! my front wheel flew out of my dropout... Things like that don't just
happen. Something's gotta be wrong before it happens. What that is: user error, malfunction, who
knows. But to happen spontaneously? Ummm, yeah...

Mike

 

[Jobst Brandt]

Mike Shaw writes:

> I just did the test that Jobst recommended and indeed, my disc equipped wheel migrated back and
> down when there was no clamping pressure applied by the QR. However, once there was pressure
> applied by the QR, this tendency was overcome.

How much pressure? Wellllll, if I brake harder, it will take even more pressure than on my bicycle
with conventional fork and rim brakes. How much? This variable setting defines the safe bicycle in
this respect. I am glad my safety has not been defined by how tight I make my QR. Besides, as has
been discussed here often in this forum, most front-wheel bearings fail from QR preload. The
over-center feel of a QR comes from stretch in the skewer and compression of the hollow axle. That
compression usually overloads the previously correctly adjusted bearings.

> The only way I can see my front wheel ejecting itself spontaneously from my forks is if the QR is
> either installed incorrectly, breaks, or there's a massive side load that pulls the wheel
> partially out of the dropout first.

That side load on the QR does not occur because a wheel will collapse from a load great enough to
extract the wheel with a freshly adjusted QR. Wheels are amazingly weak to side loads but because
the bicycle is a balanced single track vehicle (only light lateral loads) they do not suffer this
failure. This is true even during a broadslide. A wheel separating side load would throw the rider
to the ground... or occur as a result of crashing.

However, the massive load you mention is furnished by the disc brake. The separation force arises
from the ratio of tire rolling radius divided by brake disc radius minus (the axle load) one. Since
this ratio for common disc brakes, lies between 3 and 4, they can cause a force (on one side of the
axle) of as much as 500lbf. This can occur with hard braking on hard surface with the rear wheel at
lift-off for a combined rider and bicycle weight of 200lbs.

> In the first instance, it is still user error. The second is equipment failure which would be
> possible to be caught in time with proper maintenance. The third would probably mean that you
> have to stop riding and fix your wheel before continuing, allowing you to tighten an otherwise
> loose QR.

So in your opinion, is this reasonable condition for a bicycle sold to the public at large?

> I can see how using Ti QRs would be asking for trouble when running discs. I can also see that
> filing off the "lawyer lips" on a disc brake equipped bike is not a good thing either, if just for
> the additional insurance "just in case."

What difference should QR material make. Both are intended to secure the wheel. The way you say
that, it seems there is a thin line between a safe QR closure and an unsafe one.

> I can also see why I wouldn't want my disc caliper on the front of my fork. That much delicate
> stuff right in the way of trees, rocks, etc. What the "answer" is, I haven't a clue.

Oh you rascal. You ride under tough conditions exceeding imagination. You probably drive an SUV with
chromed jungle grills over the front with bumper bars to help you get to the real rough stuff to
ride bike. How well do you think your fork blades sustain running into rocks. This sounds like so
much Rambo. Where's Sylvester Stallone when we need him?

> Questions that just popped into my mind:

> Exactly how much force does it take to eject the wheel from a properly tightened QR/fork
> interface? How much force is a "typical" QR exerting? Exactly where is the tendency of the wheel
> to come out of the bottom of the fork equal to the clamping force of the QR? How much force is the
> disc brake exerting on the QR/fork interface? How deep would a dropout have to be to keep a wheel
> in the fork? Maybe a "J" shaped dropout would work?

You say that as if I and others have not given that any thought. I guess you just began reading
about this because the suggestions you offer have all been analyzed here. The different shaped
dropout has also been shown to not solve the problem.

Jobst Brandt [email protected] Palo Alto CA

 

[James Annan]

Mike S. wrote:
> . Further independent testing and examination
>
>>has verified- in a preliminary fashion at least- both the ejection force and the loosening of QRs.
>>
>
> When was the last time a QR came undone spontaneously? Snagged on trees, bushes, bashed on rocks,
> yes. Loosen completely on its own? Hmmm... don't think so.

I received this by email recently, from a shop owner who was setting up a bike for a customer:

"Well, just in the parking lot, the disc will demonstrably begin to pull the wheel out of the drop
out. A few on-off cycles of braking and the nut can be seen backing off, if you keep it up, the QR
is loose enough to clear the lawyer tabs in just a minute of this action, mind you just in the
parking lot."

I guess that particular parking lot has more than its fair share of rocks and bushes to snag
the lever on.

Ben Cooper is another shop owner who has done similar tests and found a correctly fastened skewer
loosening repeatedly under very light use. If you massively overtighten the skewer, as many MTBers
have learnt by experience to do, you can reduce the likelihood of this occurring but there is no way
of knowing in advance how tight is tight enough, nor how much this overtensioning increases the
likelihood of snapping the skewer, another `operator error' that can have very serious consequences.

James

 

[Spider]

David Damerell <[email protected]> wrote in message
news:<CfD*[email protected]>...
> Spider <[email protected]> wrote:
> >How was the 0.6g decelleration figure arrived at? (This is one I've had a problem with from the
> >beginning - I don't know where to get a g-meter for my mtb. I would be willing to experiment if I
> >had one.)
>
> As was explained to you at the time

Why is this bit of condescension necessary? I just don't get why you folks think that this makes
your case more solid.

> the maximum deceleration attainable without lifting the rear wheel on the flat is directly
> determined by the angle between the horizontal and a line drawn through the forward contact patch
> and the centre of gravity of the bike+rider.

Yes, it's a nice theory. Too bad that's not the way it works in application.

1.) What is the coeffcient of friction of the two materials, acting together (travelling surface
and tire)?

2.) Since when does braking only happen on level ground? (This could *increase* the number, as the
CG may change.) In fact, braking most often happens on a slope. The number needs to be
recalculated.

3.) Most riders change their CG during braking, especially on a hill. An endo at speed is not
indicated for happy riding, so, the rider will shift his/her posterior back to change the weight
distribution. This also changes the calculation.

4.) On dirt, I have NEVER only used the front brake. The rear is always part of the equation. How
much is being used? I dont' know, and neither does Mr. Annan. This changes the calculation - by
some unknown amount.

Now, if someone could list the mu of knobby tire on dirt (sand, mud, etc) then we could see some
numbers that are not at the most extreme end of the spectrum, but something that a little closer to
what really happens.

Spider

 

[Spider]

"Mike S." <mikeshaw2@coxDOTnet> wrote in message news:<PrL3b.32217$cj1.11028@fed1read06>...
> <[email protected]> wrote in message
> news:[email protected]...

> > This is intended to demonstrate that there is a separating force, something that has been argued
> > here at length.
>
> Yeah, and I'll bet that if you did the same with cantis or V-brakes, it'd do the same thing. Since
> I haven't tried it, I don't know. Anyone willing to try?
>
> I've got an F3000 out in the garage that I can experiment with in a bit. I'll let you know what
> happens.

From James' website, the free-body diagram shows clearly that there is an ejection force. It's quite
simple. The magnitude might not be accurate (due to an optimistic decel figure of 0.6g) but the
force exists. A lot of the questions you ask here have been answered previously, and especially on
James' web site.

Spider