Carlton Reid on QR safety

David Martin wrote:
Ed Pirrero wrote:
- would
take at least a week.

Actually, I thought up a test in my head in about thirty seconds. It
would actually require someone to do some real work, instead of tapping
on a keyboard, but I guess that's really the big impediment here,
right? Sheer laziness.

How long would it take to *perform* the tests though?

Less time than it takes to mentally masturbate in usenet.

And how many incidents of bikes with rim brakes have had the same thing
happen?

Zero, AFAIK.

Of course, you haven't even bothered to look. When I was riding my
cruiser bike, I once came off a curb and had the wheel come out of one
of the drop outs. Turned the bars and threw me right onto the
sidewalk. That bike had no front brake at all.

There's one.

So your cruiser bike with *no front brake at all* has the wheel drop
out under gravity and you think this is an appropriate exampel to show
that a front wheel drops out through the influence of braking with rim
brakes?

I didn't claim it had anything to do with braking forces. It had
everything to do with gravity and user error. But just because a bike
has disk brakes DOES NOT MEAN that gravity and user error are not also
present. How do you separate out all those effects?

So far, nobody has even bothered.

Bizarre. If you can't get simple things right, how could one trust a
single thing you say.

LOL. Irony.

If you pretend otherwise, say so.

I don't pretend - it's happened to me, before disk-brake bikes even
existed. And I've had other front wheel incidents after transport that
were quite obviously user error.

All with rim brakes.

No, one which you state with no brakes at all.

Read what you're responding to before you respond.

If not, quit asking
distracting, hypothetical and irrelevant questions.

LOL. You do know what a "control group" is, right, Frank? If not,
then we're done here.

Would you explain why you actually need a control group in this
situation and what form it would take?

Differentiating the wheel separations due entirely to disk brake use as
compared to regular user error/equipment misapplication.

No, it doesn't. The force exists. Whether or not it's "dangerous" has
not yet been answered.

That has been answered.

Well, thank goodness for that! Where's the data?

It has resulted in several experienced riders
being seriously injured.

And the critical analyses are where? Oh, that's right - they were
caused by disk brakes because *James said so*.

Maybe it happened the way James thinks. Maybe it didn't. Nobody
knows, because nobody has actually critically looked at any of the
accidents and the aftermath. Has James even set his eyes on the bikes
in question? No? Then how the hell does he know exactly what
happened?

The debate then centres on whether the
cost/benefit of fixing this is appropriate.

Actually, it doesn't. If there is sufficient evidence that the design
is dangerous, then the money shouldn't matter.

The major criterion for not going the qr20 route is that these wheels
are at present somewhat specialist rather than the common q/r standard.

So what? The more forks that are made that way, the more hubs that
will get into the supply chain. If all MTB forks were QR20, don't you
think ALL hub manufacturers would have OEM deals for QR20 hubs to bike
makers???

The easy route is to mount the caliper on the front, just as brake
bosses are mounted on the front.

But since that's not going to happen, it seems something else will
probably happen. Or nothing else will.

E.P.

"Marz" wrote in message
oups.com...

Jay Beattie wrote:
In fact, most of the hard braking on an MTB is on the rear
wheel. ...
. -- Jay Beattie.


Dude! Most of you braking should be appled to the front wheel.
If
you're jamming on the rear brake, you're not slowing you're
slidding.

Oh and the rest of your post was wrong too.

Dude! You are not going to lock up your front wheel on loose dirt
because it is really hard, dude, to control a front wheel skid.
More back brake than front on loose terrain, dude. That's what
I'm getting at. In fact you lock up your rear even on purpose
sometimes to carve that big, dirt churning turn, dude. Try that
on the front wheel for a little fun sometime, dude. -- Jay
Beattie.

Jay Beattie wrote:
"Marz" wrote in message
oups.com...

Jay Beattie wrote:

In fact, most of the hard braking on an MTB is on the rear

wheel. ...

. -- Jay Beattie.


Dude! Most of you braking should be appled to the front wheel.

If

you're jamming on the rear brake, you're not slowing you're

slidding.

Oh and the rest of your post was wrong too.


Dude! You are not going to lock up your front wheel on loose dirt
because it is really hard, dude, to control a front wheel skid.

Dude! Have you ever ridden off-road? It's easy to control a front
wheel skid in loose dirt.

More back brake than front on loose terrain, dude. That's what
I'm getting at. In fact you lock up your rear even on purpose
sometimes to carve that big, dirt churning turn, dude. Try that
on the front wheel for a little fun sometime, dude.

Not a problem for anyone with the slightest bit of balance.

Keep your roadie paradigms to yourself.

Greg
--
"All my time I spent in heaven
Revelries of dance and wine
Waking to the sound of laughter
Up I'd rise and kiss the sky" - The Mekons

Ed Pirrero wrote:
David Martin wrote:
Ed Pirrero wrote:
And how many incidents of bikes with rim brakes have had the same thing
happen?

Zero, AFAIK.

Of course, you haven't even bothered to look. When I was riding my
cruiser bike, I once came off a curb and had the wheel come out of one
of the drop outs. Turned the bars and threw me right onto the
sidewalk. That bike had no front brake at all.

There's one.

So your cruiser bike with *no front brake at all* has the wheel drop
out under gravity and you think this is an appropriate exampel to show
that a front wheel drops out through the influence of braking with rim
brakes?

I didn't claim it had anything to do with braking forces. It had
everything to do with gravity and user error.

You miss the point. When asked for an example of a bike with rim brakes
showing a front wheel ejection you post an example of a bike without
rim brakes.

Bizarre. If you can't get simple things right, how could one trust a
single thing you say.

LOL. Irony.

At least I know the difference between a rim brake and no brake.

I don't pretend - it's happened to me, before disk-brake bikes even
existed. And I've had other front wheel incidents after transport that
were quite obviously user error.

All with rim brakes.

No, one which you state with no brakes at all.

Read what you're responding to before you respond.

In the set of incidents which you have reported, not all of them were
wheels equipped with rim brakes. Is (not all) != all too difficult to
comprehend?

...d

Jay Beattie wrote:
"Marz" wrote in message
oups.com...

Jay Beattie wrote:
In fact, most of the hard braking on an MTB is on the rear
wheel. ...
. -- Jay Beattie.


Dude! Most of you braking should be appled to the front wheel.
If
you're jamming on the rear brake, you're not slowing you're
slidding.

Oh and the rest of your post was wrong too.

Dude! You are not going to lock up your front wheel on loose dirt
because it is really hard, dude, to control a front wheel skid.
More back brake than front on loose terrain, dude. That's what
I'm getting at. In fact you lock up your rear even on purpose
sometimes to carve that big, dirt churning turn, dude. Try that
on the front wheel for a little fun sometime, dude. -- Jay
Beattie.


0 for 2, you're not doing so good.

If you want to stop on loose stuff quickly, use your front brake. Even
if it's steep loose stuff, still use your front brake.

If the front wheel starts to skid, modulate your braking.

Try it on a flat piece of dirt road, get up to speed and try using
front then back brake to stop. Which one stops you quicker? Don't
forget to get your arse behind your saddle if you're really hammering
that front brake.

If you want a laugh, try taking an off camber loose corner at speed and
locking both wheels. You'll need to weight the inside edge of your
tyres while you slighty counter steer to drift around the corner. Only
works at speed. It's more like skiing than riding.


Laters dude,

Marz

Ed Pirrero wrote:
David Martin wrote:
Ed Pirrero wrote:
- would
take at least a week.

Actually, I thought up a test in my head in about thirty seconds. It
would actually require someone to do some real work, instead of tapping
on a keyboard, but I guess that's really the big impediment here,
right? Sheer laziness.

How long would it take to *perform* the tests though?

Less time than it takes to [family newsgroup, buddy] in usenet.

Sounds like an interesting test. Details?

--
Dave
dvt at psu dot edu

On Thu, 16 Feb 2006 12:36:31 -0800, Jay Beattie wrote:

The more important
point was that from a wheel ejection/disc brake standpoint, if your are
sliding either wheel, then you are not getting the ejection forces
theorized in this thread which, apparently, assume infinite traction.

Yes and no. Infinite traction does not give infinite braking capability.
Once above a coefficient of friction better than 0.6 - 0.7 any extra
does no good because the rider will either be over the bars or using
superior skill to pull a "stoppie". In either case the actual "G" is
going to be 0.6 - 0.7 So assume infinite traction if you wish, it makes
no difference to the forces we are discussing.


Mike

Ian Blake writes:

It is possible to generate more than 0.6g deceleration
momentarily. Others have written in this NG about the peak forces
possible on rough terrain. But I don't think many people ride
that hard.

Racers and those into "xtreme" riding, yes. But those are a tiny

Everybody does extreme braking. Everyday I descend a steep hill
around a blind bend to a T-Junction with a busier road. The
slightest bit of exuberance might result in an urgent need for heavy
braking. (Its the reason I have disc brakes on a commuter bike.
Wet rim brakes were far too exciting for me).

It doesn't take a "racer" or any other extreme user to cause a 1g
retardation. Bumpy trails with embedded river bottom rock cause
intermittent airborne travel and if descending, applying the brake
will cause a hard rock skid, brief as that may be.

Locally, in the Forest of Nisene Marks, I have met plenty of
descending riders making the usual crunch-crunch bouncing skids as
they head into turns. This is not unusual and occurs often.

Jobst Brandt

On Thu, 16 Feb 2006 15:43:38 +0000, Tony Raven wrote:

Tim McNamara wrote:
Those calculations were based on real
world numbers, published measurements of pull-out resistance, and
minor things like the laws of physics.

Your calculations are all fine except that you keep considering pull out
forces in the absence of lawyers lips. Now most disk brake forks have
lawyers lips. With them the pull out forces are probably at least an
order of magnitude higher because you need to physically push them out
the way or stretch the skewer so it passes over them.

I didn't even have to appeal
to the issue of transverse cyclic forces to show that the problem
exists.

Only because you and everyone else keep ignoring the presence and
influence of the lawyers lips. If you include them you have to resort

Lawyers Lips are a fail safe back up system. They are not the prime method of
holding the axle in place. This thread is about failure of the primary system.

No one is disputing that Lawyers Lips will prevent total release of the wheel
even with a partially open QR.

In my experience of Lawyers Lips on an old bike (my current bikes do not have
them). There was certainly room between the fail safe stop position and the
position I closed the QR. There may still be room for my problem with the
disc brake to occur. (Wheel twists in dropout, The angle partially engages the
brake, very annoying).

Jay Beattie wrote:
. The more
important point was that from a wheel ejection/disc brake
standpoint, if your are sliding either wheel, then you are not
getting the ejection forces theorized in this thread which,
apparently, assume infinite traction.

Forces at the front contact patch can be greater than what's usually
assumed, especially off road.

Usually, people think in terms of a deceleration limit imposed by
pitchover. "You can't apply that much force, because you'll go over
the bars."

But you can have transient forces that are much larger than the force
necessary for pitchover. On the road, it's much more unlikely, but on
rough off-road, you can envision near-tangential impacts of rocks, etc.
with the tire's perimeter. The force goes away as soon as the tire
clears the rock, so the rotational inertia of the rider&bike prevents
instantaneous pitchover. But the force the QR has to deal with (if
it's a typical disk brake) can be momentarily very large.

- Frank Krygowski