Disc brake front wheel ejection: fact or fantasy?

"With so many amateur riders out there it's amazing that front wheels aren't
falling off left, right and centre"
Amateurs are not the only ones who can screw up. About 6-7 years ago I was
looking to buy a new bike. At a well regarded bike shop I was going to test
ride a bike, the salesmen adjusted the seat and then gave the bike to the
mechanic to check before I took it out. I don't know what he checked
because the quick release on the front brake was open and with it open did
not contact the rim enough to stop the bike. I tried to brake at a stop
sign and no front brake. A car very nearly hit me as I crossed the highway.
It was a very vivid lesson in who is responsible to check a bike before it
is ridden. Check the brakes, check the skewers, bounce the bike and see
what shakes, check the handle bars and seats to see there tight. That
should take about 15 sec if every thing is ok and may be life saver if they
are not
Chris


"Westie" wrote in message
...

"Doug Taylor" wrote in message
...
The boys (the girls are too sensible, it seems) in rec.bicycles.tech
are going at it once again on this subject, with the tech heads and
roadies basically saying that you are taking your life in your hands
if you use disc brakes with QR's and regular dropouts on the theory
that the QR eventually will come loose under force of the front brake
and your wheel will pop off.

So, my question is: has anybody who actually rides mountain bike with
any frequency (such as the amb crowd) experienced this phenomenon or
heard of anybody loosing a wheel? If so, any serious injuries? Is
the sky really falling or can we get back on our bikes and ride?

--dt

Most likely more than half of the people out there that ride 'mountain
bikes' have never heard of this issue and wouldn't know where to find a
'quick release skewer' on their bikes if they had to. Many of the pure
recreational riders and Dewbies that I know just aren't interested in
regular equipment checks. They'll check it if it happens, otherwise
ignorance is bliss and they'll ride it 'til it breaks.

With so many amateur riders out there it's amazing that front wheels
aren't
falling off left, right and centre. And not from braking forces - just
from
lack of proper adjustment.
--
Westie

On Mon, 01 Sep 2003 16:53:10 -0700, Monique Y. Herman wrote:

I specifically asked a LBS about bike maintenance classes, and the
salesguy claimed that he knew of no such thing in the area.

Check your local community ed. Oh yeah, and other bike shops, assuming
you have them. Stuff like adjusting your brakes and derailleur aren't
that difficult once you know where the screws are.

I've heard good things about _Zinn and the Art of Mt Bike Maintenance_,
but can't vouch for it myself as I haven't found a copy yet.

And there's always Sheldon "Hottie" Brown's website:
http://www.sheldonbrown.com/harris/index.htm

HTH
gabrielle

Alex Bird said...

Why would discs be more likely to release the wheel? This makes no
sense to me.

Alex

There is a theory, conjured by one person by the name of James Annan,
who rides a tandem mountain bike, and a few roadies who don't ride
mountain bikes at all, that repeated use of the disc brake loosens the
skewer, and when the skewer is loose enough, the brake ejects the wheel
out of the dropout. There have been no documented cases of it ever
having actually happened to anyone, except to maybe James Annan himself.
Myself, Doug Taylor and Spider have been the main people taking the
skeptical side of the debate over in rec.bicycles.tech. James Annan
wants to attribute every wheel loss, and seemingly every off-road biking
injury, to his pet theory. He is quite close-minded to any opposing
viewpoint. I believe that it actually happened to him, but his was a
very special case. He was on a tandem which can exert extreme forces in
braking, much more than you would see on a single person bike. Worse,
his fork was very poorly designed. It almost looked like it was built to
have this failure. It had no retention lips and this feature alone would
have almost certainly prevented the wheel from going anywhere. The fork
also had a very odd dropout angle that slanted toward the rear and ran
parallel with the brake rotor. Vertical dropouts would have resisted
some of the ejection force.

Now he is badgering bicycle manufacturers, journalists and the American
Consumer Product Safety Commission, not to mention us on the Internet,
that something must be done about it. The fact that almost nobody who
actually uses bikes so equipped believes him or takes his scare tactics
seriously doesn't faze him in the least. My opinion is that retention
lips make this failure almost impossible. This opinion is backed up by
the fact that nobody can find any cases of it happening to anyone but
him. His bike didn't have them, the vast majority of bike sold in the US
do and have for years. Europe may be different.

gabrielle said...

On Mon, 01 Sep 2003 15:24:57 -0700, bomba wrote:

Not quite the same thing. He popped a wheelie off a kerb, the wheel
fell out, chucked him over the bars and the bike then somersaulted in to
his head. Bet he couldn't do that again if he tried

That was from 999, and was way longer than 3 or 4 years ago.

I don't think they had disk brakes back then.

gabrielle

Oh yeah. William the Conqueror defeated King Harold at the Battle of
Hastings riding mountain bikes.

On Mon, 01 Sep 2003 18:33:25 -0700, gabrielle penned:
On Mon, 01 Sep 2003 16:53:10 -0700, Monique Y. Herman wrote:

I specifically asked a LBS about bike maintenance classes, and the
salesguy claimed that he knew of no such thing in the area.

Check your local community ed. Oh yeah, and other bike shops, assuming
you have them. Stuff like adjusting your brakes and derailleur aren't
that difficult once you know where the screws are.

I've heard good things about _Zinn and the Art of Mt Bike Maintenance_,
but can't vouch for it myself as I haven't found a copy yet.

And there's always Sheldon "Hottie" Brown's website:
http://www.sheldonbrown.com/harris/index.htm

HTH
gabrielle

Thanks for the pointers. I have to admit to being a bit wary of
shifters -- I tried to "tune" the gears on a bike I had while in college
on the theory of, "How complicated could this possibly be?" ...
Needless to say, with no knowledge whatsoever, that bike never shifted
properly again.

The best way to deal with a fear is to meet it head-on, though, right?
--
monique

Doug Taylor wrote in message . ..
The boys (the girls are too sensible, it seems) in rec.bicycles.tech
are going at it once again on this subject, with the tech heads and
roadies basically saying that you are taking your life in your hands
if you use disc brakes with QR's and regular dropouts on the theory
that the QR eventually will come loose under force of the front brake
and your wheel will pop off.

Roadies and especially the bunch at rectum.bisexual.techsticles are a
bunch of sissy punkasses.

JD

Super Slinky wrote in message et...

There is a theory, conjured by one person by the name of James Annan,
who rides a tandem mountain bike, and a few roadies who don't ride
mountain bikes at all, that repeated use of the disc brake loosens the
skewer, and when the skewer is loose enough, the brake ejects the wheel
out of the dropout.

The fact that almost nobody who
actually uses bikes so equipped believes him or takes his scare tactics
seriously doesn't faze him in the least.

The fact that trolls like yourself lie about me on usenet certainly
doesn't faze me in the least. I'm not stupid and I realised right from
the start that with so many powerful vested interests involved I was
going to end up the scapegoat anyway, it's tough **** but that's what
whistleblowers have always got for their trouble. I don't want it to
be _my_ campaign but neither am I prepared to sit back and do nothing
while the manufacturers stick their heads in the sand and riders
continue to get seriously hurt by this design fault.

Several of the journalists who have written about this (and who all
agree that there is a real problem, having reviewed the ample evidence
in its favour) are in fact trained engineers with long experience in
the bicycle industry, and some of the most respected expert witnesses
in bicycle liability litigation bar none (also trained engineers) have
stated their clear opinion that there is a dangerous fault. Many
people have now replicated the phenomenon by themselves, no special
equipment required, and it is increasingly ridiculous that the
manufacturers pretend they don't know about it. Some people who work
in the industry, who know for sure there is a problem, have stated
that they don't want bodies such as the CPSC involved precisely
because they _do_ know there is a real problem, and it's going to cost
someone quite a lot of money to fix.

Of course, the longer this drags on, the more it will cost when it
eventually does get fixed. But you'd rather attack me than actually
ask the manufacturers for some answers. That says plenty about your
motivation and interest in this problem. Never mind, it will
eventually be solved, but it will be despite your contribution rather
than with the help of it. You may think you are saving the
manufacturers from unnecessary interference, but you are actually
encouraging them to dig their own graves. I hope you are proud of
yourself.

James

"Doug Taylor" wrote in message
...
The boys (the girls are too sensible, it seems) in rec.bicycles.tech
are going at it once again on this subject, with the tech heads and
roadies basically saying that you are taking your life in your hands
if you use disc brakes with QR's and regular dropouts on the theory
that the QR eventually will come loose under force of the front brake
and your wheel will pop off.

So, my question is: has anybody who actually rides mountain bike with
any frequency (such as the amb crowd) experienced this phenomenon or
heard of anybody loosing a wheel? If so, any serious injuries? Is
the sky really falling or can we get back on our bikes and ride?


There has been much discussion over this issue on singletrackworld.com, not
surprising really as the issue is very close to some of the regulars. As far
as I can tell there has been no conclusive proof either way, although some
independant testing has shown that vibration from disc brake forces can lead
to a loosening of the Q.R. nut the testing has not been rigerous enough to
draw a verifiable conclusion. I believe its an issue that should continue to
be discussed. Just because it hasn't happened to you, or to anyone you know
doesn't mean it can't happen.

A bodge solution was put forward on the STW forum:

http://www.singletrackworld.com/foru...528093#reply_5
28933

basically it involves using a jubilee clip (hose clamp) to clamp round the
Q.R. nut with the jubilee nut resting against the fork dropouts, resisting
loosening.

If anyone is really interested there are a few more interesting discussions
on the following threads:

http://www.singletrackworld.com/foru...523608#reply_5
26529

http://www.singletrackworld.com/foru...531565#reply_5
33475

http://www.singletrackworld.com/foru...553505#reply_5
54322

Steve.

Doug Taylor wrote in message
...
The boys (the girls are too sensible, it seems) in rec.bicycles.tech
are going at it once again on this subject, with the tech heads and
roadies basically saying that you are taking your life in your hands
if you use disc brakes with QR's and regular dropouts on the theory
that the QR eventually will come loose under force of the front brake
and your wheel will pop off.

So, my question is: has anybody who actually rides mountain bike with
any frequency (such as the amb crowd) experienced this phenomenon or
heard of anybody loosing a wheel? If so, any serious injuries? Is
the sky really falling or can we get back on our bikes and ride?

Well, I got a Hope Mini on the front, with the big rotor, bike is heavy and
so is my pack. Big bad grippy knobbies, and I don't half hammer on that
brake lever some times when coming to a stop - _never_ had a problem, not
slight, not at all, never. I do get _very_ medieval on my QR skewers though
(closed 'em with my feet before now......), enough that I'm worried for the
life of my dropouts, heheheheh..........


This is my own experience only, obverously.


Shaun aRe

bomba wrote in message ...

Not quite the same thing. He popped a wheelie off a kerb, the wheel
fell out, chucked him over the bars and the bike then somersaulted in to
his head. Bet he couldn't do that again if he tried

I'm willing to bet he hasn't tried.

That was from 999, and was way longer than 3 or 4 years ago.

Nah, twas no more than five years ago, I remember where I was when I saw it.