Missy Giove's QR pops open



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Tim McNamara writes:

>> What have you observed? Are there dents in the dropout that you can click over with a screwdriver
>> or fingernail?

> I would add a further question to this for my own edification: are the impressions in the metal or
> in the paint? The reason I as is that my road bikes all have impressions in the paint from the
> knurling on the faces of the QR nuts and the locknuts on the hubs; they do not have impressions in
> the metal, however.

> And to Jobst: you mentioned the augering of the locknuts into the horizontal dropouts due to flex.
> Would unequal motion of the two legs of a suspension fork cause similar results?

I don't think so, because the knurled jam nuts were rocked fore and aft with great force, enough to
break rear axles regularly. I haven't seen any dimples in dropouts from jam nuts, but then I only
looked at a few bicycles and no used MTB's. Dropout damage and broken axles have become rare on my
bicycle since I changed to vertical dropouts years ago. Campagnolo introduced them as a product
after Cino Cinelli showed Tullio the ones I had made for my Cinelli frames, an idea I had gotten
from East German Diamant frames that I saw at the Rome Olympics.

Jobst Brandt [email protected] Palo Alto CA
 
In article <[email protected]>,
Chris Phillipo <[email protected]> wrote:

> > > > If that were the case, then no nut or bolt would ever work loose. And yet they do, hence the
> > > > market for things like Loctite and Nylock nuts,
> > >
> > > QR levers have Nylock nuts and serrated edges, are you starting to get the picture yet?
> >
> > Some do. Some don't.
>
> Alright I'll throw you a bone on this one Tim, if you have a QR that has no nyloc insert and has
> smooth faced fasteners, then yes I believe it not only can slip, it will slip and should be
> illegal for sale. I certainly wouldn't sell one.

Well, you should really e-mail Shimano and Campagnolo on this, since both of them make such QRs.
Hmmm, Mavic too, come to think of it.

> >
> > > Tell me oh great one, why in your opinion does only the nut on the right move and not the
> > > lever on the left side which is identical in every way that matters? Is your voodoo magic a
> > > liberal or a conservative?
> >
> > The forces involved are conservative, of course. ;-) In fact, they're downright Newt-onian. The
> > disk is only on one side of the wheel, being designed by obviously a bunch of Commie leftists.
> > Don't even get me started on those pinkos at Cannondale with their Lefty shock fork, nor about
> > Mike Burrows and his one-sided front *and* rear wheel mounts (at least those are balanced by
> > having one on the right and one on the left).
> > :-D
> >
> > The reason is simple: the axle us pushed towards the end of the dropout on the left side upon
> > braking, which in turn puts a bending force on the right end of the skewer and axle. When the
> > brake is released and possibly when you hit a bump, the axle is reseated at the top of the slot.
> > Repeat every time you brake, hundreds of times perhaps in an hour. I imagine that a light
> > feathering of the brakes has little effect, BTW. Over time, this movement (which I think is
> > likely to be exacerbated by uneven fork leg compression) allows the retaining nut on the end of
> > the skewer to back off, lowering tension on the skewer.
>
> Well then if this is true, to solve this "problem" one only needs to install the QR so that the
> lever is on the right had side and wedged against the fork so that it can not spin. If it did move
> it would be blatantly obvious be the direction the lever is pointing.

Interesting idea. However, that still fails to solve the real problem, which is that disk brakes
cause an ejection force on the wheel. That's what's faulty in the design, and that's what needs to
be fixed. The rest of this discussion is a distraction from the real issue and a red herring.
 
In article <[email protected]>,
Chris Phillipo <[email protected]> wrote:

> In article <[email protected]>, [email protected] says...
> > Chris Phillipo wrote:
> > >
> > > Are you kidding me. Any breaking force on the wheel is trying to force the wheel out of
> > > verticle dropouts.
> >
> > No, a braking force applied at the top of the rim tends to force the axle back in the dropouts
> > rather than down. Unless I've missed your point altogether.
>
> It tends to force the wheel backwards with the road surface in the equation. Try it with no QR
> skewer and see if your wheel stays on.

Apparently you missed my response to this previously. Like most riders, I have had the experience of
forgetting to close a QR skewer before starting to ride- only to have someone say "dude, your skewer
is open." I brake to a stop, close the skewer and ride on. The wheel does not eject from the
dropouts whether the front or the rear.

You can flip the bike over (thereby eliminating restraint by the road surface), open the QR, spin
the wheel in the appropriate direction, hit the brakes and the wheel won't pop out even if you spin
the wheel as fast as you can. Unless you have a front disk brake, because the current design placing
the caliper behind the fork leg creates an ejection force.

The whole point of what James Annan's analysis indicates is that this *is* a faulty design. A design
that creates an ejection force on the front wheel is inherently faulty- whether or not the rider
properly uses the QR skewer or not. The design is flawed and needs to be revised. That implies a
recall of all current disk forks and either an adapter to move the caliper to the front of the fork,
or replacement with a corrected design. Expensive for the fork industry, yes, but they should have
caught this in the initial design stages.

You can continue to waste electrons arguing that "it's user error" until your fingers are blue, and
you're still wrong. The design is flawed because it places ejection forces on the front wheel. The
lawyer lips discussion is largely a red herring, as Jobst points out, and I apologize for having
gotten sucked into it. There's no point in continuing it in this thread, IMHO, because it's
unresolveable here. The issue is really in the hands of the fork manufacturers, the CPSC and the EU
equivalent.
 
In article <[email protected]>,
Chris Phillipo <[email protected]> wrote:

> If you want to see a wheel slip, try replacing your QR with solid axle and a nut/flat washer
> arrangment.

Thanks, I already have that arrangement on my track bike. It never slips.
 
In article <[email protected]>,
Chris Phillipo <[email protected]> wrote:

> > > what there is disagreement over is how this then translated into the real world with a
> > > retained wheel.
> >
> > You are thinking that the act of closing the QR skewer changes the magnitude or directions of
> > the forces involved?
>
> You think that it doesn't? Tell me Tim, how exactly does the wheel pull down on the drop outs
> whent here is no QR installed? Or are you now saying it does not do with with the QR installed?
> That would completely invalidate your argument.

You've never taken a class in logic, I'm guessing. Either that or you are simply letting your
dudgeon overcome your common sense. You're not even phrasing your questions coherently any more.

The forces caused by the disk brake are exactly the same whether the QR is tightened or not. It
tries to push the axle out of the dropouts.
 
In article <[email protected]>,
Chris Phillipo <[email protected]> wrote:

> Well, if you are indeed worried about the difference that 10" of distance is making in the in the
> overall leverage calculation, I suggest you have a 26" disc rotor made, peraps dual rotors just to
> be safe. That should give you the effect you are looking for from your bike upside down with the
> QR removed.

ROTFL! I actually already have 24.5" dual rotor disk brakes on my wheels. They're a revolutionary
product called "rims."

> I'm going to go ride mine, thanks.

Enjoy!
 
"Tim McNamara" <[email protected]> wrote

> Interesting idea. However, that still fails to solve the real problem, which is that disk brakes
> cause an ejection force on the wheel. That's what's faulty in the design, and that's what needs to
> be fixed. The rest of this discussion is a distraction from the real issue and a red herring.

The pertinant question is: Does a disk brake impart sufficient force to overcome the clamping force
of a properly tightened quick release mechanism, as they are currently designed?

Saying that it is a faulty design is incorrect, because the real question has not been asked
nor answered.

Pete
 
Pete who? writes:

>> Interesting idea. However, that still fails to solve the real problem, which is that disk brakes
>> cause an ejection force on the wheel. That's what's faulty in the design, and that's what needs
>> to be fixed. The rest of this discussion is a distraction from the real issue and a red herring.

> The pertinent question is: Does a disk brake impart sufficient force to overcome the clamping
> force of a properly tightened quick release mechanism, as they are currently designed?

Whether one can take preventive measures against wheel separation or not has nothing to do with the
design flaw that this represents. When the brake is used, there is a net disengaging force that
should not and need not arise.

> Saying that it is a faulty design is incorrect, because the real question has not been asked nor
> answered.

There is no second question to the disengagement force that was not analyzed and is being ignored at
the moment.

Jobst Brandt [email protected] Palo Alto CA
 
On Fri, 30 May 2003 12:33:59 GMT, [email protected] wrote:

>They have no effect if they don't make an indentation in the mating part.

They will *always* deform the mating part slightly, even if only elastically, but just because you
can't see it without a microscope doesn't mean there is no inelastic deformation.

Also, I don't think the deep grooves theory is necessarily correct: it presupposes that the QR nut
will always hit the fork in exactly the same way. There is no reason for that to be so, except when
the deformations induced are exceptionally large, as opposed to small.

Jasper
 
A Muzi wrote:

> But is that effect significant?

For those who are seriously injured, I believe so.

> Can a rider allow that vibration/hysteresis/creep to continue for a good long while without
> noticing a loud and annoying brake disc rubbing? Or hearing the ting-ting-ting of a skewer lever
> flopping around?

It is clear that the entire failure can progress from start to finish during a single bumpy fast
descent. The rider has a lot to concentrate on, and a lot of distractions, rather than paying close
attention to some (barely perceptible, through much of the process) loss of rigidity at the fork.

Often they do notice the loose skewer, once it has progressed sufficiently far. Sometimes, they stop
safely, and sometimes, the lever flopping around is the last thing they remember...

> Has any rider continued like that until a five or six millimeter gap has opened, enough to pass
> the raised lips at the bottom of a fork?

It only has to pass over one lip at a time. In any case, surely it is beyond contention that these
incidents occur, the only question some of you still have is as to their cause. In either case, the
skewer _is_ loose enough to pass over the lips, since it indisputably does so.

> I can't imagine a mechanism which would further unscrew the skewer nut after it isn't pressed
> against the fork tips any longer. Remember they are nylock.

Some are, but some certainly aren't. Even without 'further unscrewing', the lever flopping open will
add substantial clearance. The total clearance of initial unscrewing plus lever opening only has to
clear a single lip.

Your scepticism could be more accurately aimed at those who claim that the 'operator error' of an
incorrectly closed lever is the root cause of the failure. In that case, the lever opens first (by
hypothesis) and then the skewer has to unscrew significantly, while under no tension at all, and all
the while the rider has to not notice that the front wheel is completely loose. The other way round
(gradual unscrewing, followed by a sudden lever opening and immediate wheel loss) seems far more
plausible for several reasons. Firstly, the unscrewing is forced by skewer tension, and secondly,
there is much less chance of noticing the failure since the skewer is only slightly loose through
most of the process. Most importantly, it explains how many riders can experience unscrewing of the
skewer prior to any other sign of failure, a compelling piece of evidence that the 'sceptics' have
absolutely no plausible explanation for.

James
 
In article <[email protected]>, "Pete" <[email protected]> wrote:

> "Tim McNamara" <[email protected]> wrote
>
> > Interesting idea. However, that still fails to solve the real problem, which is that disk brakes
> > cause an ejection force on the wheel. That's what's faulty in the design, and that's what needs
> > to be fixed. The rest of this discussion is a distraction from the real issue and a red herring.
>
> The pertinant question is: Does a disk brake impart sufficient force to overcome the clamping
> force of a properly tightened quick release mechanism, as they are currently designed?

You're apparently new to this thread (and the others on this topic). That is exactly what has been
debated thus far. The analysis of the forces involved demonstrates that a disk brake does produce an
ejection force on the wheel strong enough to overcome the skewer's clamping force.

The pertinent question is: does a disk brake, as mounted on all current suspension forks, produce a
force that tries to eject the axle out of the dropout? The answer is yes.

> Saying that it is a faulty design is incorrect, because the real question has not been asked nor
> answered.

The question has been asked, the question has been answered. The design is faulty. It should have
been caught and rectified in the initial design stages. It wasn't.
 
Pete wrote:

> The pertinant question is: Does a disk brake impart sufficient force to overcome the clamping
> force of a properly tightened quick release mechanism, as they are currently designed?

The obvious answer to that it a resounding YES. I thought the only thing the sceptics (excepting
perhaps a few of the more stupid ones) were questioning, is whether this can result in the skewer
unscrewing.

Actually, I think that between them, the sceptics believe all aspects of the failure, it's just that
none of them have got the whole picture yet. Either the force isn't big enough (but the failure
would occur if it was), or the force is plenty big enough (but nevertheless it won't unscrew, cos
"I've never seen it"). If only they would just sort it all out by themselves....

James
 
<[email protected]> wrote in message news:[email protected]...
> Chris Snell writes:
>
> > However, I do not believe that the forces tending to unscrew a knurled QR have been shown to be
> > sufficient to cause said QR to actually unscrew. Where is the analysis of this part of James
> > theory? I believe the knurling is there for a reason. I believe the reason is to prevent
> > unscrewing. I believe this indicates someone has already thought about this.
>
> I don't believe that all QR faces have knurling on them. My Campagnolo and Shimano QR's have
> smooth faces and that leads me to believe others may also. That would be one point to investigate
> on the wheel that separated and those of users who noted more looseness after use than before.
>
> > Do we agree that the web page that James Annan links to says that
a
> > circumferential row of teeth under the screw head is sufficient to prevent loosening?
>
> I'm sorry, I didn't follow that link so I don't know what it said
and
> don't know where that might be. Could you point me that way?

http://www.boltscience.com/pages/vibloose.htm

>
> > Do we agree that knurled QR's have a circumferential row of teeth under the screw head?
>
> They may, I don't have any at hand as I said. Mine have knurling around the lever head and nut but
> none on the pressure face. The
hubs
> I have were made for road bicycles where it would not be in the interest of the rider to have
> knurling there. The knurling is on
the
> jam nuts but even they do not make a dent in my steel Campagnolo dropouts. I don't tighten them
> that tight and am not even sure I could. I know that I once burst a Campagnolo QR head by too much
> preload during closure.
>
I have four types (shimano road, shimano mtb, salsa, unknown but not the previous types) of QR. They
all have knurling similar to the QR in the diagram at the top of this page:

http://bike.shimano.com/product_images/HB/ev_images/HB_M750_EV.pdf

Although this diagram shows more of the "crenelated" type knurling than my actual samples. In my
actual samples the knurling is from the outer edge of the surface that contacts the drop out, to the
inner edge. Again, all on the face that contacts the drop out.

> > So can we proceed from here?
>
> Of course, but where are we headed? I'm just pursuing the concept that there is a problem and that
> picking at nits surrounding the problem is not going to make it go away, especially when failure
> mechanisms are dismissed without reasonable cause.
>
> Jobst Brandt [email protected] Palo Alto CA

Where are we headed? Good question. I am trying to establish what I said earlier. The unscrewing
problem only affects smooth QR's.

I would also like to apologize to rec.bicycles.tech. I did not notice until this afternoon that this
thread was cross-posted there. Stupid me, I should have known better. Any "color commentary" that I
wrote was under the now-obviously-incorrect assumption that it was destined only for
alt.mountain-bike, where it might not seem as out of place.

- Chris.
 
> Mark Hickey writes:
>
> > You missed what is (to me at least) the most puzzling aspect of this whole thing. How can the
> > wheel get loose enough to be ejected without being obvious to the rider? On a bike with disc
> > brakes, you'll be experiencing some world-class brake drag long before the skewer is open enough
> > to be forced over even the wimpiest lawyer lips.

<[email protected]> wrote in message news:[email protected]...
> That is not the case. I visited my local bicycle shop, opened the QR on a disc brake bicycle and
> demonstrated the downward movement of the axle when the brake was applied. The wheel did not
> disengage because it stopped on the retention lips. The bicycle could be ridden around the shop
> with no indication that the QR was open until braking. The motion this caused at the axle in the
> dropout would not be noticeable on uneven terrain.
>
> Other than that, I think skewer stretching has been misinterpreted. A change in length of skewer
> (and axle) are the elastic compliance felt when closing a QR lever. This amounts to 0.010-0.015
> inch for normal closure. It is not an elongation of the skewer to the point of clearing retention
> lips. The length change subject comes up regularly in wheel bearing adjustment because this axle
> compression overloads bearings that were adjusted with no clearance before QR closure.

OK that all seems reasonable to me. But then how does a skewer get past the lips?

I understand Mr Annan's fork was lacking those lips and also had the fork tips oddly positioned at
the most unfavoable angle for use with a disc.

But there were several comments in this thread implying the skewer would not retain the wheel in
the normal setup.

I'm not just being argumentative. I'm asking because (although the tandem was a fully explicable
failure) there's an attempt to extend the argument to include regular production disc-equipped bikes
with lips on the ends and a normal steel skewer.

Lastly, I understand how a bicycle ridden around a showroom or parking lot works without a skewer.
But offroad, wouldn't there be regular tire-off-ground moments to show up the loose wheel rubbing
the disc and wandering side to side?

As you know, I am not a mounatin bike expert. I could be misinterpreting this.
--
Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971
 
"Chris Snell" <[email protected]> wrote in message
news:<[email protected]>...

> Do we agree that the web page that James Annan links to says that a circumferential row of teeth
> under the screw head is sufficient to prevent loosening?

No, it doesn't say that.

It is made absolutely clear on the page that the locking methods described provide 'resistance to
vibration loosening' rather than automatically preventing it. It is also abundantly clear that the
only way a knurled surface will prevent unscrewing, is if the surfaces interlock sufficiently well
to prevent slip. It seems likely that knurling will help somewhat, but it is certainly not always
adequate. My rear knurled Shimano XT QR slips regularly at 'standard' tension, it is an uncommon
frame design with an awkwardly angled dropout. This is a well known problem with this particular
frame design, which has been changed as a result.

James
 
"James Annan" <[email protected]> wrote in message
news:[email protected]...
> "Chris Snell" <[email protected]> wrote in message
news:<[email protected]>...
>
> > Do we agree that the web page that James Annan links to says that
a
> > circumferential row of teeth under the screw head is sufficient to prevent loosening?
>
> No, it doesn't say that.
>
> It is made absolutely clear on the page that the locking methods described provide 'resistance to
> vibration loosening' rather than automatically preventing it. It is also abundantly clear that the
only
> way a knurled surface will prevent unscrewing, is if the surfaces interlock sufficiently well to
> prevent slip. It seems likely that knurling will help somewhat, but it is certainly not always
adequate.
>
> James

But I don't see anywhere on that page that says it is garanteed to be ineffective to prevent
vibration loosening, either.

Unless you are saying it is impossible to prevent a sliding fastener from unscrewing.

- Chris.
 
<[email protected]> wrote in message news:[email protected]...
> Pete who? writes:
>
> >> Interesting idea. However, that still fails to solve the real problem, which is that disk
> >> brakes cause an ejection force on the wheel. That's what's faulty in the design, and that's
> >> what needs to be fixed. The rest of this discussion is a distraction from
the
> >> real issue and a red herring.
>
> > The pertinent question is: Does a disk brake impart sufficient
force
> > to overcome the clamping force of a properly tightened quick
release
> > mechanism, as they are currently designed?
>
> Whether one can take preventive measures against wheel separation or not has nothing to do with
> the design flaw that this represents.
When
> the brake is used, there is a net disengaging force that should not and need not arise.
>
> Jobst Brandt [email protected] Palo Alto CA

Are suggesting putting the caliper in front of the fork? I think it will be prone to damage there.

- Chris.
 
"Tim McNamara" <[email protected]> wrote in message
news:[email protected]...
> In article <[email protected]>, [email protected] wrote:
>
> > What have you observed? Are there dents in the dropout that you
can
> > click over with a screwdriver or fingernail?
>
> I would add a further question to this for my own edification: are the impressions in the metal or
> in the paint? The reason I as is
that
> my road bikes all have impressions in the paint from the knurling on the faces of the QR nuts and
> the locknuts on the hubs; they do not have impressions in the metal, however.

Metal. The aluminum dropouts on the carbon fork are not painted. There is no paint left on the Kona
fork where the QR clamps. On the Specialized steel fork the paint is almost entirely gone, and where
it is gone the indentations are in the metal, where it's not gone I wouldn't like guess whether the
metal underneath has been deformed. Keep in mind this fork only has 10 rides on it.

- Chris.
 
Chris Snell wrote:

> But I don't see anywhere on that page that says it is garanteed to be ineffective to prevent
> vibration loosening, either.

Nothing is certain but death, taxes and the persistent stupidity of usenet trolls.

However most of them seem to have been scared off by my question:

>> What operator error do you believe can be responsible for the QR unscrewing? Or do you simply
>> not accept that the QR does unscrew?

which Tony Raven conspicuously ducked and no-one else responded to either.

James
 
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