Re: More on disk brakes and wheel ejection

[Chris Zacho The Wheelman]

TTT

May you have the wind at your back.
And a really low gear for the hills!
Chris

Chris'Z Corner
"The Website for the Common Bicyclist":
http://www.geocities.com/czcorner

[[email protected]]

Tim McNamara > writes:


> Well, this is still preliminary research and whilst it will
> undoubtedly put a bit of a rocket up the proverbial of many fork
> manufacturers from our point of view as riders of disc equipped
> bikes a little perspective is in order. Whilst it is looking like
> there seems to be an emerging problem the incidences of actual
> accidents that can be attributed to skewers undoing are clearly very
> small. Common sense coupled with a routine of skewer checking
> whilst out on the trails will most likely be enough to limit the
> problem to a very small risk. In short there is nothing here that
> suggests mountain bikers with disc brakes should panic and revert
> back to V-brakes. As they say in the science world, more research is
> needed.

I disagree. A free body diagram shows that forces from a "rear of
fork mounted" brake caliper exerts a downward force on the axle and
that it is greater than a dropout without retention lips will hold
under "normal" closure force. How QR skewers unscrew from vertical
axle motion caused by these brake forces has been explained and
proven by tests, leaving the "you didn't close it right" apologists
out of the running.

We don't need no steenkin further research, as they say. All that is
needed is to move the caliper ahead of the fork, nothing more. In my
estimation, this is the only reasonable solution that would
conclusively solve the problem.

I cannot understand what all the hand wringing is about. Just do it!
This is fretting at its worst.

Jobst Brandt

Palo Alto CA

[John Rees]

> wrote in message
...
> Tim McNamara > writes:
>
>
> > Well, this is still preliminary research and whilst it will
> > undoubtedly put a bit of a rocket up the proverbial of many fork
> > manufacturers from our point of view as riders of disc equipped
> > bikes a little perspective is in order. Whilst it is looking like
> > there seems to be an emerging problem the incidences of actual
> > accidents that can be attributed to skewers undoing are clearly very
> > small. Common sense coupled with a routine of skewer checking
> > whilst out on the trails will most likely be enough to limit the
> > problem to a very small risk. In short there is nothing here that
> > suggests mountain bikers with disc brakes should panic and revert
> > back to V-brakes. As they say in the science world, more research is
> > needed.
>
> I disagree. A free body diagram shows that forces from a "rear of
> fork mounted" brake caliper exerts a downward force on the axle and
> that it is greater than a dropout without retention lips will hold
> under "normal" closure force. How QR skewers unscrew from vertical
> axle motion caused by these brake forces has been explained and
> proven by tests, leaving the "you didn't close it right" apologists
> out of the running.
>
> We don't need no steenkin further research, as they say. All that is
> needed is to move the caliper ahead of the fork, nothing more. In my
> estimation, this is the only reasonable solution that would
> conclusively solve the problem.
>
> I cannot understand what all the hand wringing is about. Just do it!
> This is fretting at its worst.

Whether or not the calliper is moved on the forks there's a lot of expensive
bikes out there that will not or cannot get retrofitted. How about Salsa or
someone coming out with a front skewer with left handed threads for these
bikes. Would that help?
John Rees

[[email protected]]

John Rees writes:

>>> Well, this is still preliminary research and whilst it will
>>> undoubtedly put a bit of a rocket up the proverbial of many fork
>>> manufacturers from our point of view as riders of disc equipped
>>> bikes a little perspective is in order. Whilst it is looking like
>>> there seems to be an emerging problem the incidences of actual
>>> accidents that can be attributed to skewers undoing are clearly
>>> very small. Common sense coupled with a routine of skewer
>>> checking whilst out on the trails will most likely be enough to
>>> limit the problem to a very small risk. In short there is nothing
>>> here that suggests mountain bikers with disc brakes should panic
>>> and revert back to V-brakes. As they say in the science world,
>>> more research is needed.

>> I disagree. A free body diagram shows that forces from a "rear of
>> fork mounted" brake caliper exerts a downward force on the axle and
>> that it is greater than a dropout without retention lips will hold
>> under "normal" closure force. How QR skewers unscrew from vertical
>> axle motion caused by these brake forces has been explained and
>> proven by tests, leaving the "you didn't close it right" apologists
>> out of the running.

>> We don't need no steenkin further research, as they say. All that
>> is needed is to move the caliper ahead of the fork, nothing more.
>> In my estimation, this is the only reasonable solution that would
>> conclusively solve the problem.

>> I cannot understand what all the hand wringing is about. Just do
>> it! This is fretting at its worst.

> Whether or not the caliper is moved on the forks there's a lot of
> expensive bikes out there that will not or cannot get retrofitted.
> How about Salsa or someone coming out with a front skewer with left
> handed threads for these bikes. Would that help?

I didn't mention anything about prior equipment nor did the above
comments. The question is what to do about the problem for the
future. How the recall and retrofit occurs is a separate matter.
That people are wringing their hands about whether it is a real
problem and whether it even needs repair is the main problem here.
There are many in this forum that are still defending the status quo.

Left handed thread??? Please explain what effect that should have.
We already discussed that inserting the skewer from the other side
doesn't help much and only then when the lever snags something when it
unscrews. However, the reason it unscrews is that it isn't holding
and moves up and down in the dropout between braking and riding over
bumps.

Jobst Brandt

Palo Alto CA

[[email protected]]

John Rees writes:

>>> Well, this is still preliminary research and whilst it will
>>> undoubtedly put a bit of a rocket up the proverbial of many fork
>>> manufacturers from our point of view as riders of disc equipped
>>> bikes a little perspective is in order. Whilst it is looking like
>>> there seems to be an emerging problem the incidences of actual
>>> accidents that can be attributed to skewers undoing are clearly
>>> very small. Common sense coupled with a routine of skewer
>>> checking whilst out on the trails will most likely be enough to
>>> limit the problem to a very small risk. In short there is nothing
>>> here that suggests mountain bikers with disc brakes should panic
>>> and revert back to V-brakes. As they say in the science world,
>>> more research is needed.

>> I disagree. A free body diagram shows that forces from a "rear of
>> fork mounted" brake caliper exerts a downward force on the axle and
>> that it is greater than a dropout without retention lips will hold
>> under "normal" closure force. How QR skewers unscrew from vertical
>> axle motion caused by these brake forces has been explained and
>> proven by tests, leaving the "you didn't close it right" apologists
>> out of the running.

>> We don't need no steenkin further research, as they say. All that
>> is needed is to move the caliper ahead of the fork, nothing more.
>> In my estimation, this is the only reasonable solution that would
>> conclusively solve the problem.

>> I cannot understand what all the hand wringing is about. Just do
>> it! This is fretting at its worst.

> Whether or not the caliper is moved on the forks there's a lot of
> expensive bikes out there that will not or cannot get retrofitted.
> How about Salsa or someone coming out with a front skewer with left
> handed threads for these bikes. Would that help?

I didn't mention anything about prior equipment nor did the above
comments. The question is what to do about the problem for the
future. How the recall and retrofit occurs is a separate matter.
That people are wringing their hands about whether it is a real
problem and whether it even needs repair is the main problem here.
There are many who are still defending the status quo in this forum.

Left handed thread??? Please explain what effect that could have.
We already discussed that inserting the skewer from the other side
doesn't help much and only then when the lever snags something when it
unscrews. However, the reason it unscrews is that it isn't holding
and moves up and down in the dropout between braking and riding over
bumps.

Jobst Brandt

Palo Alto CA

[Spider]

wrote in message >...
> Tim McNamara > writes:
>
>
> > Well, this is still preliminary research and whilst it will
> > undoubtedly put a bit of a rocket up the proverbial of many fork
> > manufacturers from our point of view as riders of disc equipped
> > bikes a little perspective is in order. Whilst it is looking like
> > there seems to be an emerging problem the incidences of actual
> > accidents that can be attributed to skewers undoing are clearly very
> > small. Common sense coupled with a routine of skewer checking
> > whilst out on the trails will most likely be enough to limit the
> > problem to a very small risk. In short there is nothing here that
> > suggests mountain bikers with disc brakes should panic and revert
> > back to V-brakes. As they say in the science world, more research is
> > needed.
>
> I disagree.

Why? AFAIK, there has been *no* experiemental research done on this
system. If there are published articles, could you please post a
link? I am very interested.

> A free body diagram

A free-body diagram is useful in showing the *potential* problem, but
it in no way proves anything.


> shows that forces from a "rear of
> fork mounted" brake caliper exerts a downward force on the axle and
> that it is greater than a dropout without retention lips will hold
> under "normal" closure force.

"Without retention lips" is a key line. I wonder - how many
disk-brake-capable forks lack retention lips? I do not count
user-removed lips in this.

> How QR skewers unscrew from vertical
> axle motion caused by these brake forces has been explained and
> proven by tests, leaving the "you didn't close it right" apologists
> out of the running.

Sorry, but I have not seen the tests that were run on QR skewers in
disk-brake-equipped forks. Could you point out those articles?

The fact is that until very recently, nobody enven thought of such a
thing. Using cyclic movement in other systems does *suggest* the
possiblity, but does not *prove* that it happens in the system that we
are discussing. Hypothesis <> proof.

The unproven "you didn't close it right" hypothesis is co-equal with
the same, unproven cyclic-motion hypothesis.

> We don't need no steenkin further research, as they say.

The fact that no experimental research has been published makes this
statement hilarious. All that exists are the free-body diagram that
may or may not be an accurate description of all the forces involved,
and an extention of a known phenomenon of cyclic loading which may or
may not promote asymmetric "unscrewing forces" on skewers.

> All that is
> needed is to move the caliper ahead of the fork, nothing more.

Finally, we agree on something, at least in part. Non-QR axle
retention systems (QR20, or some such) might also solve the problem.

Or a stronger skewer.


> In my
> estimation, this is the only reasonable solution that would
> conclusively solve the problem.

Assuming, of course, that the problem actually exists. I have yet to
see anything more than connect-the-dots hypotheses.

> I cannot understand what all the hand wringing is about. Just do it!
> This is fretting at its worst.

The hand-wringing is over the solid fact that very few of these
failures occur. The fact that they DO occur does not imply that there
is a fundemental design flaw in the system. While I do agree that the
system is not optimal, the entire bicycle, from frame to tires, is a
compromise. Strength, weight, convenience, efficiency. Everything.

There is also the inconvenient fact that the failures are not a given,
and do not happen 100% on all disk-brake/fork systems. This implies
that some PART of the system may be more at fault than another, and
that the design is adequate (if not optimal) but the execution, in
some cases, is inadequate. Dangerously so, in fact.

So, I have a solution that is easier than cheaper than your's:

If someone is worried about disk brakes and ejection, they should
convert to a non-disk-brake system. Cheap and easy.

I'm not going to hold my breath over getting real data on this.
"Because I said so," or "because it's theoretically possible" aren't
good enough answers.

Spider

[Sheldon Brown]

Quoth Jobst:

> We don't need no steenkin further research, as they say. All that is
> needed is to move the caliper ahead of the fork, nothing more. In my
> estimation, this is the only reasonable solution that would
> conclusively solve the problem.

That would require re-desining the calipers, n'es-ce pas?

What about changing the angle of the wheel slot in the fork ends to make
it perpendicular to the braking reaction force? This would seem a lot
easier to do.

Forgive me if this has already been suggested and dismissed for some
good reason--I haven't been reading all of the posts in this looooong
thread.

Sheldon "Four O'Clock" Brown
+-----------------------------------------------------------+
| Sometimes the only thing more dangerous than a question |
| is an answer. --Ferengi Rule of Acquisition #208 |
+-----------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

[[email protected]]

John Rees writes:

>>>> I disagree. A free body diagram shows that forces from a "rear
>>>> of fork mounted" brake caliper exerts a downward force on the
>>>> axle and that it is greater than a dropout without retention lips
>>>> will hold under "normal" closure force. How QR skewers unscrew
>>>> from vertical axle motion caused by these brake forces has been
>>>> explained and proven by tests, leaving the "you didn't close it
>>>> right" apologists out of the running.

>>>> We don't need no steenkin further research, as they say. All
>>>> that is needed is to move the caliper ahead of the fork, nothing
>>>> more. In my estimation, this is the only reasonable solution
>>>> that would conclusively solve the problem.

>>>> I cannot understand what all the hand wringing is about. Just do
>>>> it! This is fretting at its worst.

>>> Whether or not the caliper is moved on the forks there's a lot of
>>> expensive bikes out there that will not or cannot get retrofitted.
>>> How about Salsa or someone coming out with a front skewer with
>>> left handed threads for these bikes. Would that help?

>> I didn't mention anything about prior equipment nor did the above
>> comments. The question is what to do about the problem for the
>> future. How the recall and retrofit occurs is a separate matter.
>> That people are wringing their hands about whether it is a real
>> problem and whether it even needs repair is the main problem here.
>> There are many in this forum that are still defending the status
>> quo.

> Well, I didn't see the rest of the discussion. Your post stands as
> the first in the thread on my newsreader. The post you responded to
> and quoted was undated, makes it tough for me to located the
> original thread..

That's a problem between you and your newsreader. It has no effect on
presenting technical arguments, suggesting that others "think about
it" is a bit rude, especially when the writer hasn't done so.
Loosening screws is a common occurrence in machinery for sound
reasons. Tightening a screw takes more torque than loosening so with
random roughness and motion, loosening is the preferred direction of
rotation. By your logic screws should not be lying along roads where
they have unscrewed themselves from their designed position.

> Why even have a dropout? Since there isn't a yellow motorcycle chasing XC
> riders around in races to make quick wheel changes, why is there a need for
> a super quick release on a mountain suspension fork in the first place?

I take it you don't ride bike. I for one prefer to change my flat
tires using a patch kit and not needing a wrench to remove the wheel.
When I start a ride I also like to grab a suitable wheel from by
"armory" and quickly and simply attach it to my bicycle.

> How about a closed dropout with a new standard for attaching the
> front wheel?

I see, you are trying to make friends with the many bicyclists who
enjoy having easily changeable wheels. I don't think you are being any
more realistic about this than your tightening theory. At about this
point your admonition to "think about it" comes to mind.

> Why stick with a design that predates:
> - Mountain bikes.
> - Suspension forks.
> - Disc brakes.
> The time seems to have arrived to rethink the entire front wheel
> attachment.

That and the concept of four wheels on a car, front engines and doors
that open to the rear and many other things that have shown their
worth pragmatically over millions of vehicles. maybe we should review
the air cooled ace engine and solid axles again.

I'm sure you should think about it!

Jobst Brandt

Palo Alto CA

[[email protected]]

anonymous snipes rudely from cover:

> The hand-wringing is over the solid fact that very few of these
> failures occur. The fact that they DO occur does not imply that
> there is a fundemental design flaw in the system. While I do agree
> that the system is not optimal, the entire bicycle, from frame to
> tires, is a compromise. Strength, weight, convenience, efficiency.
> Everything.

Just because you are too lazy to review the tests and incidents that
have been presented doesn't mean there is no evidence and no obvious
design flaw in the current arrangement of disk brakes. Just about any
moderately astute mechanical engineer recognizes the magnitude of this
flaw on inspection, without ever making a measurement.

> There is also the inconvenient fact that the failures are not a
> given, and do not happen 100% on all disk-brake/fork systems. This
> implies that some PART of the system may be more at fault than
> another, and that the design is adequate (if not optimal) but the
> execution, in some cases, is inadequate. Dangerously so, in fact.

Talk to the rider in the wheelchair whose wheel separation brought
focus to this problem that was previously pushed aside because there
were no serious injuries YET. Mountain bikers are expected to fall.
Why failures are less common than one might expect has also been
statistically explained here on this forum. If you were interested,
you could look this up in deja news or Google. I will not do your
library search.

> So, I have a solution that is easier than cheaper than your's:

> If someone is worried about disk brakes and ejection, they should
> convert to a non-disk-brake system. Cheap and easy.

Others can ride their booby trapped bicycles while remembering to not
leave the wheels in the frame over a longer number of rides and not to
make hard braking stops such as upon landing from a jump.

> I'm not going to hold my breath over getting real data on this.
> "Because I said so," or "because it's theoretically possible" aren't
> good enough answers.

As you snipe from the sidelines, manufacturers and merchant are giving
their liability serious thought. Of course as a non combatant you can
offer all sorts of inane solutions to what you consider a non-problem.
I don't understand what motivates you to take this stance that
benefits no one. I'm sure you have not testified in a bicycle
liability suit but your smug style and off kilter advice would not be
seen favorably by the court or the jury.

Jobst Brandt

Palo Alto CA

[[email protected]]

Sheldon Brown writes:

>> We don't need no steenkin further research, as they say. All that
>> is needed is to move the caliper ahead of the fork, nothing more.
>> In my estimation, this is the only reasonable solution that would
>> conclusively solve the problem.

> That would require re-designing the calipers, n'es-ce pas?

> What about changing the angle of the wheel slot in the fork ends to
> make it perpendicular to the braking reaction force? This would
> seem a lot easier to do.

I think we went through all that. As long as the braking forces are
down and the wheel loads are up, the axle will move and the QR will
unscrew. Therefore, changing the dropout slot orientation is only a
bandaid and does not attack the underlying problem. The caliper must
be in front so that its reaction forces are in the same direction as
the wheel load forces. Only then will the reliable retention of the
wheel be assured.

> Forgive me if this has already been suggested and dismissed for some
> good reason--I haven't been reading all of the posts in this
> looooong thread.

Well, it hasn't been put this way before but it has been part of the
argument for caliper placement. I'm glad you brought it up again so
that that aspect does not get lost.

Jobst Brandt

Palo Alto CA

[Rick Onanian]

I should put on lead armor before diving into this thread, but....

On Fri, 01 Aug 2003 17:20:24 GMT, > wrote:
>> How about a closed dropout with a new standard for attaching the
>> front wheel?
>
> I see, you are trying to make friends with the many bicyclists who
> enjoy having easily changeable wheels. I don't think you are being any
> more realistic about this than your tightening theory. At about this
> point your admonition to "think about it" comes to mind.

Why is the current QR system the _only_ one that could be easy?

On my mountain bike, I have to flip the QR lever and then
hand-unscrew the opposite side of the skewer partway. Why not
close the dropout slots into holes, and make a skewer that's
just a little quicker to unscrew all the way off and pull out
of the wheel?

Then, no tools required, and pretty much the same time to
remove and replace the wheel. The only situation where it
could be a problem is in a race.

I imagine the only thing to change from the current system is
the dropout, and minor change to skewers (which could still fit
in existing wheels and be used in existing slotted dropouts).

Disclaimer: I don't know what I'm talking about, and am a damn
fool. There, I said it for you. <G>

> Jobst Brandt
>
> Palo Alto CA
--
Rick Onanian

[Stergios Papadakis]

Rick Onanian wrote:

> Why is the current QR system the _only_ one that could be easy?
>
> On my mountain bike, I have to flip the QR lever and then
> hand-unscrew the opposite side of the skewer partway. Why not
> close the dropout slots into holes, and make a skewer that's
> just a little quicker to unscrew all the way off and pull out
> of the wheel?
>
> Then, no tools required, and pretty much the same time to
> remove and replace the wheel. The only situation where it
> could be a problem is in a race.
>
> I imagine the only thing to change from the current system is
> the dropout, and minor change to skewers (which could still fit
> in existing wheels and be used in existing slotted dropouts).
>
> Disclaimer: I don't know what I'm talking about, and am a damn
> fool. There, I said it for you. <G>

I'm not sure what you are envisioning.
You would then have to flex the fork legs outward to
fit the axle, and most forks are too stiff to
be flexed easily by that amount.

This doesn't solve the problem anyway. There
will be some play when the axle is fit into
its hole. It would still get pushed up and down
to the extent of that play by braking and bump
forces. The play wouldn't result in wheel ejection,
but it still isn't good design.

Stergios

[Chris Zacho The Wheelman]

(Stergios=A0Papadakis) wrote:
<snipped>

>I'm with Jobst. The simplest calculation
>shows that normal braking forces put a
>load on the axle that is larger than the
>ISO standard which the skewers are
>designed to. That should be the end of
>the discussion.

>The fact that certain skewers, when used
>on certain forks, exceed the standard by
>enough that failures don't happen daily is
>irrelevant. Nobody can know which
>combinations are safe and which aren't
>unless all permutations are tested. That
>would obviously be stupid. Standards are
>created in order to make such
>foolishness unnecessary.

>Fork makers, put the caliper where it
>belongs and be done with it. Then, your
>marketing division can come up with an
>ad explaining how the altered CG of the
>fork improves both control when
>descending and front-wheel traction
>when climbing.

>Stergios

The only _other_ solutions would be to add a cap to the end of the
dropouts, look at a motorcycle fork for a heavyweight example of this,
or some sort of "locking skewer" that _couldn't_ unscrew without some
voluntary action by the rider first. Maybe something along the lines of
the freehub lockring?

But I also agree with Jobst. simply putting the brake calipers in front
would be the easiest solution. And you don't need any calculations to
see this, it can be easily demonstrated. Hold your arms out in front of
your body, like a front fork, hold a wheel in your hands and spin it
"forwards".

Now have someone grab the spokes where the present location of a disk
brake caliper would be. You can feel the axle trying to pull itself
downwards, out of your hands! Now, in your imagination, add the inertia
of the bike, rider, etc...

Now try the same thing again, but this time have him grab the wheel in
"front" of your arms.

Repositioning the calipers wouldn't cause any problems with retrofit on
older frames, as the brake mounting has nothing whatsoever to do with
the attachment of the forks to the frame. The brake may end up on the
opposite side of the front wheel than the back, but that would ba a
small price to pay, I would think.

Sure, many front disks haven't evicted their wheels, but many Ford
Pintos didn't explode, either!

May you have the wind at your back.
And a really low gear for the hills!
Chris

Chris'Z Corner
"The Website for the Common Bicyclist":
http://www.geocities.com/czcorner

[Rick Onanian]

On Fri, 01 Aug 2003 15:35:38 -0400, Stergios Papadakis
> wrote:
> I'm not sure what you are envisioning.
> You would then have to flex the fork legs outward to
> fit the axle, and most forks are too stiff to
> be flexed easily by that amount.

No, you'd just pull the skewer right out of the wheel.

> This doesn't solve the problem anyway. There
> will be some play when the axle is fit into
> its hole. It would still get pushed up and down
> to the extent of that play by braking and bump
> forces. The play wouldn't result in wheel ejection,
> but it still isn't good design.

Well, I'm no engineer, but an engineer could probably
come up with something like my idea but better. Or,
just make the dropout holes the same size as the hole
in the hub -- the hub doesn't have any play up and down
on the skewer.

> Stergios
--
Rick Onanian

[Dave Lehnen]

Sheldon Brown wrote:
> Quoth Jobst:
>
>> We don't need no steenkin further research, as they say. All that is
>> needed is to move the caliper ahead of the fork, nothing more. In my
>> estimation, this is the only reasonable solution that would
>> conclusively solve the problem.
>
>
> That would require re-desining the calipers, n'es-ce pas?
>
<snip>

If the caliper is moved from the rear of the left fork to the front
of the right fork, the hydraulic line or cable would still exit in
about the correct (upwards) direction.

Dave Lehnen

[Stergios Papadakis]

Rick Onanian wrote:
>

> No, you'd just pull the skewer right out of the wheel.
>

You should go look at your bike.
The front wheel's axle fits into the dropouts.
It is not just the skewer in the dropouts.
Go ahead and pull your skewer out with someone
sitting on the bike. The skewer is a skinny
piece of metal because it is only supposed to
be loaded in tension. The outside of the axle
presses against the top of the dropout slot when
the skewer is removed.



The skewer has enough play that it slides through the
hole in the axle. That is enough.

What you are proposing is dangerous.
You are proposing eliminating the part of the axle that
extends into the dropout. That would not only make
it difficult to line up the axle with the little holes
and get the skewer through, but it would load the
skewer in shear if you ever adjusted it with any load
on the bike.

Stergios

[Rick Onanian]

On Fri, 01 Aug 2003 17:25:53 -0400, Stergios Papadakis
> wrote:
>> No, you'd just pull the skewer right out of the wheel.
>
> You should go look at your bike.
> The front wheel's axle fits into the dropouts. It is not just the skewer
> in the dropouts. Go ahead and pull your skewer out with someone

I knew there was a reason why it wouldn't work...but I
figured I'd suggest it anyway.

As soon as I read this far, I remembered just how it
goes together, and why it wouldn't work.

> What you are proposing is dangerous.

Agreed.

I guess a new system would, in fact, have to be made
which wouldn't be compatible with old skewers and hubs,
but I suspect it could be made compatible with old
dropouts...not that anybody would have any reason to use
a new, structural-skewer wheel with old, slotted dropouts.

All of that said, I bet a proper engineer, or even myself
on a more creative day, could come up with a workable
system that's more compatible.

And, even so, it wouldn't be worth it; it has been said
over and over in this thread that moving the caliper a
little bit, or changing the angle/direction of the
dropout, would eliminate the whole issue. Sounds like
a lot easier than redesigning the QR wheel attachment
system.

> Stergios
--
Rick Onanian

[Spider]

wrote in message >...
> anonymous snipes rudely from cover:

Ahh, Mr. Brandt - already starting, from the first line with ad
hominem commentary.

1.) Ad hominem commentary is usually reserved for those who cannot
discussion issues logically,

2.) or whose argument is weak from first principles. The
distractions of attacking the writer does a fine job of deflecting
criticism from weak points.

Google up "spider" and "pseudonym" in rec.bicycles.tech for my reasons
for remaining anonymous in USENET. You will see that my credibility
with you is far down on my list of concerns.

I also recognize that my requests for information have been ignored -
either they do not exist, or they do not support your position.

> > The hand-wringing is over the solid fact that very few of these
> > failures occur. The fact that they DO occur does not imply that
> > there is a fundemental design flaw in the system. While I do agree
> > that the system is not optimal, the entire bicycle, from frame to
> > tires, is a compromise. Strength, weight, convenience, efficiency.
> > Everything.
>
> Just because you are too lazy to review the tests and incidents that
> have been presented doesn't mean there is no evidence and no obvious
> design flaw in the current arrangement of disk brakes.

Two logical fallacies in one sentence. 1.) Another ad hominem
comment (it also happens to be a strawman; I'll show that later.) 2.)
A strawman. I did not claim that there was "no evidence." In fact,
I have agreed that there may indeed be a problem.

> Just about any
> moderately astute mechanical engineer recognizes the magnitude of this
> flaw on inspection, without ever making a measurement.

Of course, this implies that the mechanical engineers employed in the
bicycle industry are not even moderately astute. Those employed by
the fork and brake manufacturers do not know what the heck they are
doing, according to Jobst Brandt. An interesting implication, but
we'll just dismiss it as hilariously false, OK?

I notice that in your book, open right here in front of me, are some
really nice tables and graphs. In particular, the graphs on p.125
(Fig. 68.)

Did you arrive at those graphs without making measurements? You imply
in your text on p. 124 that you actually, physically tested them, and
describe the apparatus. Why, might I ask, is this required for such a
simple mechanical system (a spoke), but not required for a more
complicated system like a fork/skewer/disk brake set-up?

> > There is also the inconvenient fact that the failures are not a
> > given, and do not happen 100% on all disk-brake/fork systems. This
> > implies that some PART of the system may be more at fault than
> > another, and that the design is adequate (if not optimal) but the
> > execution, in some cases, is inadequate. Dangerously so, in fact.
>
> Talk to the rider in the wheelchair whose wheel separation brought
> focus to this problem that was previously pushed aside because there
> were no serious injuries YET.

Red herring. Nobody advocates solid seatposts or handlebars, etc,
etc, etc. If there is indeed a systematic problem, then I agree that
it must be solved. But iuntil such time as it's PROVEN, with
controlled, repeatable experiments, I will reserve judgement, as any
careful scientist should.

> Mountain bikers are expected to fall.

Yes, and sometimes it happens due to user error (improperly tightened
stem bolts is one thing that jumps up first.) In fact, most falls
could probably be directly attributed to user error.

> Why failures are less common than one might expect has also been
> statistically explained here on this forum.

No, they actually have not. Neither the raw data nor the methods for
analysis are in evidence anywhere.

> If you were interested,
> you could look this up in deja news or Google.

Well, after about a half an hour of looking, I seem to be unable to
locate the raw data or the methods used to analyze them.

> I will not do your
> library search.

Of course not, especially when you're credibility is on the line.
Now, maybe you could supply a search string that makes this phantom
data appear. That might be helpful to everyone. BTW, since you make
the assertion, it is up to you to supply some evidence. Otherwise,
I'll just dismiss it as yet another red herring.

> > So, I have a solution that is easier than cheaper than your's:
>
> > If someone is worried about disk brakes and ejection, they should
> > convert to a non-disk-brake system. Cheap and easy.
>
> Others can ride their booby trapped bicycles while remembering to not
> leave the wheels in the frame over a longer number of rides and not to
> make hard braking stops such as upon landing from a jump.

Non sequitur.

My front wheel has not left the frame all season. The register marks
scribed in the fork and the skewer ends match perfectly, not even as
much as 0.25mm rotation on either side. I make hard-braking stops
often, over quite rough terrain.

> > I'm not going to hold my breath over getting real data on this.
> > "Because I said so," or "because it's theoretically possible" aren't
> > good enough answers.
>
> [ad hominem commentary snipped] manufacturers and merchant are giving
> their liability serious thought.

Serious thought <> action. In the end, they could decide that
out-of-court settlements could be cheaper than re-design/recall. I
notice, again, that no real data is forthcoming.

> Of course as a non combatant you can
> offer all sorts of inane solutions to what you consider a non-problem.

Your name-calling is tedious and beneath you. Maybe you could explain
how name-calling bolsters your position?

I own disk brakes, and use them often, on a mountain bike. 1.) I do
not consider it a "non-problem," but a *potential* problem. Why would
you mischaracterize my postings on the subject? 2.) I am right in
the middle of it, and am laying my health and safety on the line.
Unlike you, Jobst, I am actually physically dependent on the system
working. All you have to lose is a little bit of your ego, and some
luster from your reputation. I could lose my life if I am wrong. But
I do not yet believe that I am in imminent danger.

> I don't understand what motivates you to take this stance that
> benefits no one.

I am an experiemental scientist, and I am demanding the same standard
of proof that you yourself applied to bicycle wheel spoke strength.
No more, no less. If I have to pay money to get a fork and disk
caliper that are more safe, I will do so. But not until it is proven.

I am also not convinced that all factors have been taking into
account, and that issues that may appear trivial on the surface are
actually important in the proper functioning of the system.

> I'm sure you have not testified in a bicycle
> liability suit but your smug style and off kilter advice would not be
> seen favorably by the court or the jury.

Smug style? The irony is noted, Mr. Brandt. My advice to go to
V-brakes is solid, considering it is the only option open at this
moment. Tell me, Jobst - how is this advice "off-kilter" in any way?

In any case, I have read every piece of information I have seen on
this subject, since it directly effects me (or has that potential.)
Your "lazy" comment is just fluff and bluster. I suspect you would
not be so rude if you were not hiding behind the electronic curtain.

While I do not expect any hard data, or even a thoughtful reply from
you, comporting yourself in an adult fashion henceforth would be
appreciated.

Spider

[Rick Onanian]

On 1 Aug 2003 15:07:55 -0700, Spider > wrote:
> I own disk brakes, and use them often, on a mountain bike.

Often?

Do you sometimes ride that bike without using them? ;)

> Spider
--
Rick Onanian

[Tim McNamara]

In article >,
wrote:

> Tim McNamara > writes:
>
>
> > Well, this is still preliminary research and whilst it will
> > undoubtedly put a bit of a rocket up the proverbial of many fork
> > manufacturers from our point of view as riders of disc equipped
> > bikes a little perspective is in order. Whilst it is looking like
> > there seems to be an emerging problem the incidences of actual
> > accidents that can be attributed to skewers undoing are clearly
> > very small. Common sense coupled with a routine of skewer
> > checking whilst out on the trails will most likely be enough to
> > limit the problem to a very small risk. In short there is nothing
> > here that suggests mountain bikers with disc brakes should panic
> > and revert back to V-brakes. As they say in the science world,
> > more research is needed.

Whoops, wait a minute, I didn't write this! This was a quote from the
article referenced in my post.

[Tim McNamara]

In article >,
"John Rees" > wrote:

> Well, I didn't see the rest of the discussion. Your post stands as
> the first in the thread on my newsreader. The post you responded
> to and quoted was undated, makes it tough for me to located the
> original thread..

I was the original poster and let me clarify a few things. First, the
title of this thread is the title I used for my first post, but that
was several weeks ago (and it was promptly ignored by most of the loud
voices trying to shout down james Annan). The odds are it's spooled
off your news server some time ago, but you can find the original post
at Google.

You can also find a lot of other posts on this very topic- search for
James Annan as the author and you'll find them.

[Tim McNamara]

In article >,
(Spider) wrote:

> Why? AFAIK, there has been *no* experiemental research done on this
> system. If there are published articles, could you please post a
> link? I am very interested.

I did. The very first article in this thread was by me posted July
17th, prompted by seeing publication of experimental research that
confirms there *is* a problem with current disk brake fork design.
The doubting Thomases promptly ignored it.

You can find it at Google. You can also find the reference article at:

http://www.singletrackworld.com/article.php?sid=1063

[Spider]

Tim McNamara > wrote in message >...
> In article >,
> (Spider) wrote:
>
> > Why? AFAIK, there has been *no* experiemental research done on this
> > system. If there are published articles, could you please post a
> > link? I am very interested.
>
> I did.

No, you didn't. The German firm gave STW some preliminary results,
but I could not find a single, published article on this - and by that
I mean an article that describes the materials and conditions under
which the preliminary result was discovered. IOW, a scientific
article, published in a peer-reviewed journal.

> The very first article in this thread was by me posted July
> 17th, prompted by seeing publication of experimental research that
> confirms there *is* a problem with current disk brake fork design.
> The doubting Thomases promptly ignored it.

No, that article *did not* contain published work that describes the
experiment.

I apologize for not being clear on what I meant by "published
article." The world of science attaches something wholly different to
this term than the layman, and it behooves me to make that clear.

Again, my apologies.

Spider

[Maki]

In article
>,
Dave Lehnen > wrote:

> > That would require re-desining the calipers, n'es-ce pas?
> >
> <snip>
>
> If the caliper is moved from the rear of the left fork to the front
> of the right fork, the hydraulic line or cable would still exit in
> about the correct (upwards) direction.

You have to modify both the fork and the caliper mounts, so it requires
redesigning the whole system. It makes non sense to revamp the caliper
when the real problem is the hub-fork interface.

--
Fact of life #15: Heads bleed, walls don't.

[Dave Lehnen]

Maki wrote:
> In article
> >,
> Dave Lehnen > wrote:
>
>
>>>That would require re-desining the calipers, n'es-ce pas?
>>>
>>
>><snip>
>>
>>If the caliper is moved from the rear of the left fork to the front
>>of the right fork, the hydraulic line or cable would still exit in
>>about the correct (upwards) direction.
>
>
> You have to modify both the fork and the caliper mounts, so it requires
> redesigning the whole system. It makes non sense to revamp the caliper
> when the real problem is the hub-fork interface.
>

For most calipers, you only need to modify the fork, as suggested
above. An exception would be calipers like the Shimano XT, with
different diameter leading and trailing pistons.

Dave Lehnen

[Maki]

In article
>,
Dave Lehnen > wrote:

> For most calipers, you only need to modify the fork, as suggested
> above. An exception would be calipers like the Shimano XT, with
> different diameter leading and trailing pistons.

Oh, sorry. I missed the "from left to right part".
Yes, in theory it will work, but I'm not sure all the calipers are made
to brake backwards. The pads may very well be more supported in one way
than the other. And you still need to replace the fork, usually the most
expensive part.
I don't understand what's wrong with improved skewers.

--
Fact of life #15: Heads bleed, walls don't.

[Chris Zacho The Wheelman]

Why bother moving anything? Just replace the open end dropout with a
bolt on retainer, like on motorcycle F forks? Dio we really need thirty
second wheel changes on a MOUNTAIN BIKE, for Christ's sake?

May you have the wind at your back.
And a really low gear for the hills!
Chris

Chris'Z Corner
"The Website for the Common Bicyclist":
http://www.geocities.com/czcorner

[Maki]

In article >,
Rick Onanian > wrote:

> I saw skewers the other day that have a lock against
> unintentional loosening. They have a spring-loaded
> button you must press to release or turn/loosen them.
>
> Suppose these would help?

IMHO yes. Experience shows that QRs that exceed by far the current iso
standards exist, so it is clearly possible to make them strong enough.
It remains the problem of sloppy users that dont' tighteen enough, so
the QR can unscrew. With the lock this is gone too.
However the ISO standard should be updated and require a specific logo
on the skewer so that one can distinguish the good ones.

--
Fact of life #15: Heads bleed, walls don't.

[Tim McNamara]

In article >,
Maki > wrote:

> In article >,
> Rick Onanian > wrote:
>
> > I saw skewers the other day that have a lock against
> > unintentional loosening. They have a spring-loaded button you
> > must press to release or turn/loosen them.
> >
> > Suppose these would help?
>
> IMHO yes. Experience shows that QRs that exceed by far the current
> iso standards exist, so it is clearly possible to make them strong
> enough. It remains the problem of sloppy users that dont' tighteen
> enough, so the QR can unscrew.

Not so sure that this last sentence is really accurate.

[Tim McNamara]

In article >,
Maki > wrote:

> Calipers are fine where they are, the weak link is the wheel/hub
> interface.

No, the problem is that the fork design is flawed. Not the wheel/hub
interface, not the QRs, etc. The fork puts the caliper in exactly the
right place to push the wheel out of the dropout. Annan has
demonstrated this quite clearly, yet people like yourself insist on
shilly-shallying around looking for some kludge to try to overcome a
significant design flaw.

Why is this so difficult to comprehend? People's lives quite
literally depend on this. The design should be corrected to prevent
the wheel from being ejected from the dropout even if the skewer is
left open, if it unscrews, if it breaks under tension, or whatever.
The wheel should NEVER be forced out of the dropout as a result of
braking!

[[email protected]]

Maki Tartamillo writes:

>> We don't need no steenkin further research, as they say. All that
>> is needed is to move the caliper ahead of the fork, nothing more.
>> In my estimation, this is the only reasonable solution that would
>> conclusively solve the problem.

> Redesigning the QR so that it cannot unscrew is easier, cheaper, and
> backwards compatible.

Could you outline how such a device would work and how it would
prevent the axle from moving up and down alternately with braking and
normal load, the mechanism by which QR's are unscrewed?

As long as the attachment is a "dropout", having braking forces trying
to pull the wheel downward is a threatening condition that makes a
reasonably cautious rider worry about how tight is tight enough. The
less skilled or forgetful riders could fare worse. With the caliper
ahead of the fork, all these concerns are removed.

Jobst Brandt

Palo Alto CA

[[email protected]]

Chris Zacho writes:

> ...Or simply rotating the dropout slots so that the axle slides out
> forwards, perpendicular to the action of the DB.

I think you missed the test of unscrewing QR from the up and down
alternating load on the axle. This unscrews the QR as has been
tested. As long as brake reaction forces pull down on the axle and
riding loads push the axle up, The problem of loosening and failure
remain.

Jobst Brandt

Palo Alto CA

[[email protected]]

Rick Onanian writes:

>> I'm not sure what you are envisioning. You would then have to flex
>> the fork legs outward to fit the axle, and most forks are too stiff
>> to be flexed easily by that amount.

> No, you'd just pull the skewer right out of the wheel.

When you propose that, I take it you are not capturing the axle in the
dropout, as is customary with a QR, but are expecting the QR to hold
the wheel alone. In that case, the skewer would need to be about 10mm
in diameter as axles are now. What sort of axle for mounting
bearings, do you have in mind? I see these various suggestions as
incomplete designs and not practical solutions.

>> This doesn't solve the problem anyway. There will be some play
>> when the axle is fit into its hole. It would still get pushed up
>> and down to the extent of that play by braking and bump forces.
>> The play wouldn't result in wheel ejection, but it still isn't good
>> design.

> Well, I'm no engineer, but an engineer could probably come up with
> something like my idea but better. Or, just make the dropout holes
> the same size as the hole in the hub -- the hub doesn't have any
> play up and down on the skewer.

If you are not an engineer then you probably should consider axles in
holes without clearance a press fit and after some use a loose fit.
Since I cannot visualize what you have in mind, I suspect your method
has not yet been thought out to practical completion.

Jobst Brandt

Palo Alto CA

[[email protected]]

James Annan writes:

>> > wrote in message
>> ...


>>> We don't need no steenkin further research, as they say. All that
>>> is needed is to move the caliper ahead of the fork, nothing more.
>>> In my estimation, this is the only reasonable solution that would
>>> conclusively solve the problem.

>>> I cannot understand what all the hand wringing is about. Just do
>>> it! This is fretting at its worst.

>> Whether or not the caliper is moved on the forks there's a lot of
>> expensive bikes out there that will not or cannot get retrofitted.

> I'm sure you've mostly worked this out, but the reason why the
> manufacturers appear to be acting like paralyzed bunnies in
> headlights is that once their liability is established, they will be
> faced with a massive recall problem and an indeterminate backlog of
> compensation claims.

I don't think it is as bad as you describe. If manufacturers acted
now, modified their forks and recalled existing models, a solid
defense would be that the current design was general practice for all
bicycles and that no one found fault with it until a large user field
had established with a large variety of rider demands and operator
skills. This would demonstrate a good faith response to a belated
discovery that should be without major criticism. This would be
different, had there been some manufacturers who placed calipers ahead
of the fork and to whom one could point as proof of a known hazard.

What is done as retrofit is up to the industry. I see making a fail
safe "bandaid" that may not be graceful or stylish, but it could be
made safe at the expense of clean elegance. I even envisage a
retention means that would prevent the wheel from ejecting but without
trying to prevent loosening, so that essentially a "buzzer" noticeable
(looseness) would alert the rider to tighten the QR.

Jobst Brandt

Palo Alto CA

[James Annan]

wrote in message >...

>
> I don't think it is as bad as you describe. If manufacturers acted
> now, modified their forks and recalled existing models, a solid
> defense would be that the current design was general practice for all
> bicycles and that no one found fault with it until a large user field
> had established with a large variety of rider demands and operator
> skills. This would demonstrate a good faith response to a belated
> discovery that should be without major criticism.

Maybe, but I haven't heard of any forks being recalled with this
problem in the past 4 months, and in the meantime riders keep on
getting seriously hurt.

James

[Rick Onanian]

On Sat, 09 Aug 2003 07:00:40 GMT, > wrote:
>> Redesigning the QR so that it cannot unscrew is easier, cheaper, and
>> backwards compatible.
>
> Could you outline how such a device would work and how it would

I don't know how it works, but I saw skewers with a button
that must be pressed before they will screw/unscrew, in a
LBS the other day.

> prevent the axle from moving up and down alternately with braking and
> normal load, the mechanism by which QR's are unscrewed?

I suspect that preventing them from being unscrewed, along
with screwing them tight in the first place, would prevent
any issue; at least, that's the impression that I got from
this thread. It could be a wrong impression.

> As long as the attachment is a "dropout", having braking forces trying
> to pull the wheel downward is a threatening condition that makes a
> reasonably cautious rider worry about how tight is tight enough. The
> less skilled or forgetful riders could fare worse. With the caliper
> ahead of the fork, all these concerns are removed.

I agree that changing the position of the caliper and/or
changing the design of the existing open dropout system
would eliminate the safety need for a skewer that won't
unscrew.

> Jobst Brandt
>
> Palo Alto CA
--
Rick Onanian

[Rick Onanian]

On Sat, 09 Aug 2003 07:13:13 GMT, > wrote:
> Rick Onanian writes:
>> No, you'd just pull the skewer right out of the wheel.
>
> When you propose that, I take it you are not capturing the axle in the
> dropout, as is customary with a QR, but are expecting the QR to hold
> the wheel alone. In that case, the skewer would need to be about 10mm
> in diameter as axles are now. What sort of axle for mounting
> bearings, do you have in mind? I see these various suggestions as
> incomplete designs and not practical solutions.
<snip>
> Since I cannot visualize what you have in mind, I suspect your method
> has not yet been thought out to practical completion.

Very much true; somebody else mentioned similar questions,
and indeed, I realized that I did not think out the idea
to practical completion. It may be possible to create a
system similar to what I proposed, but there are certainly
better ways around the issue (like moving the caliper).

That is why I made it clear that I'm no engineer. <G>

> Jobst Brandt
>
> Palo Alto CA
--
Rick Onanian

[Robin Hubert]

I'm going to have some fun at Interbike with this one. Fox, Manitou,
RockShox, watch out!

--
Robin Hubert >

[Ryan Cousineau]

In article >,
Rick Onanian > wrote:

> On Sat, 09 Aug 2003 07:00:40 GMT, > wrote:
> >> Redesigning the QR so that it cannot unscrew is easier, cheaper, and
> >> backwards compatible.

> > As long as the attachment is a "dropout", having braking forces trying
> > to pull the wheel downward is a threatening condition that makes a
> > reasonably cautious rider worry about how tight is tight enough. The
> > less skilled or forgetful riders could fare worse. With the caliper
> > ahead of the fork, all these concerns are removed.
>
> I agree that changing the position of the caliper and/or
> changing the design of the existing open dropout system
> would eliminate the safety need for a skewer that won't
> unscrew.

Marzocchi already makes a quickly-releasable through-axle design called
the QR20:

http://www.marzocchi.com/eng/spa/products/mtb/catalogs/2003/popfeatures/q
r20.htm

It does require a hub built for a 20 mm axle, though. It's not really
aimed at disc ejection, but rather at preventing axles from breaking
under the abuse of freeriding and dirt-jumping maniacs.

--
Ryan Cousineau, http://www.sfu.ca/~rcousine
President, Fabrizio Mazzoleni Fan Club

[[email protected]]

Rick Onanian writes:

> I agree that changing the position of the caliper and/or changing
> the design of the existing open dropout system would eliminate the
> safety need for a skewer that won't unscrew.

This is a recurring theme that misses the point as I see it. A hand
installed wheel, one without a wrench tightened conical "lug nut" as
on automobile wheels, WILL move, either because it is not tight enough
to restrain all movement, or because it was inadvertently not
tightened sufficiently. As long as the disengaging force on the axle
remains, the problem remains with any manually tightened QR mechanism
that I can visualize. In this respect, I find suggestions for a
modified QR or dropout are wishful thinking.

As I said, moving the caliper ahead of the fork is an absolutely
effective solution while any modification of the dropout without it
can only appeal to riders who do not believe that the current
configuration is dangerous or that it is operator error of not
tightening the wheel sufficiently.

Jobst Brandt

Palo Alto CA

[Maki]

In article >,
Tim McNamara > wrote:

> > Calipers are fine where they are, the weak link is the wheel/hub
> > interface.
>
> No, the problem is that the fork design is flawed. Not the wheel/hub
> interface, not the QRs, etc.

Sorry, it was a typo, actually wheel/hub interface doesn't have any
sense since the hub is part of the wheel. :)
Read "fork/hub interface". The fork is obviously involved.

> The fork puts the caliper in exactly the right place to push the
> wheel out of the dropout. Annan has demonstrated this quite clearly,
> yet people like yourself insist on shilly-shallying around looking
> for some kludge to try to overcome a significant design flaw.

> Why is this so difficult to comprehend?

It isn't difficult at all and I don't disagree on James theory. Where
did I say that? I proposed a closed dropout, did you read it?

We discussed this before, do you remember? Calipers are there because
handling is better in this way. Also, calipers ahead of the fork will
pull the fork instead of pushing it. Years of motorcycle experience
shows that most people is unconfortable with that, no matter how hard
you try to convince them that the fork is solid enough.

The problem *is* the QR. Is sucks. It was designed for road bikes.
Todays MTBs have extremely high performance, that means higher stresses.
The fact that high-end freeride forks and all DH ones use different
systems proves that, brakes apart, the standard QRs are weak.
If you change the caliper position the QR is still weak.
If you change the dropout direction the QR is still weak.
The QR *needs* to be made stronger. I'm sure that not only the braking
reaction, but general vibrations, bumps, torsions and thermal stresses
have a role in loosening QRs. Did I say that the QR is weak and sucks?

What I did want to say (and sorry if I'm not always clear, but English
is not my mother tongue especially in technical field) is that if we
have to redesign forks and calipers, that are an order of magnitude more
expensive than an hub, then it makes a lot of sense to redesign
everything, starting from the real weak link, that is the QR. It make no
sense to throw away half a bicycle to save the silliest and cheapest
part of it.
Manufacturers have already started to do that on DH and FR bikes, XC
ones resists because the typical XC usage is lighter and the appeal of a
really quick relase is strong for users.

The motorcycle style hub with closed dropout that I suggested and you
didn't read isn't a kludge, but a perfectly safe (and already working on
motorcycles) solution that can be easily done with a little modify to
the fork and without touching the calipers. Then the same modified wheel
can be used *also* on existing forks: if they have lawyer lips it will
provide a sensible increment in safety, especially if threadlocking
devices are used. Not the best, but better than nothing. If you have any
criticism to this solution please tell. But don't say "it's a kludge",
tell me *why* it is.

--
Fact of life #15: Heads bleed, walls don't.

[Maki]

In article >,
wrote:

> > Redesigning the QR so that it cannot unscrew is easier, cheaper, and
> > backwards compatible.
>
> Could you outline how such a device would work and how it would
> prevent the axle from moving up and down alternately with braking and
> normal load, the mechanism by which QR's are unscrewed?

Did I say "prevent the axle from moving up and down"? No, I said "cannot
unscrew" and that means that the nut and the QR are locked, i.e. they
cannot turn. In that case they can go up and down as long as you want
and unscrewing will not happen. I posted in a past thread one possible
locking device, if you can't find it with google I'll do it for you.
I'm not saying that this is an optimal solution, but it would easily
give a lot more safety to those who already have a disk equipped MTB at
a very low cost; I would buy such a skewer for myself even if I'm not
currently using disks. Then better designs can be made for the future,
but if you expect manufacturers to recall all existing forks and
calipers you are a dreamer.

--
Fact of life #15: Heads bleed, walls don't.

[Maki]

In article >,
James Annan > wrote:

> > James, it's you that linked the QR tests on your website. When the
> > standard asked for 500N some reached 4000N or so. The current generation
> > is probaly much better.
>
> I think that's a misinterpretation. The standard had already been
> updated to 2300N rather than the earlier 500N, and I do not believe the
> skewers changed either before or since (I don't even know for which, if
> any, countries, the ISO standard is a legally-adopted requirement).

Maybe I'm wrong, but IIRC the tests were made in the early 90s and the
standard changed in 1996.
I don't have any document proving that, but a fellow on an italian NG
said that Shimano updated their QRs in 1996. He is usually very reliable.

> > one can redesign the hubs, no need to rework the fork
> > [snip]
> This 'backwards compatibility' appears to require a new front wheel (hub
> with larger hole for fatter skewer) - is this correct?

Of course. Since I premised that "at worst one can redesign the hubs" it
is quite obvious that a new hub is needed, but it costs 1/10 of a fork.
The backwards compatibility is referred to the existing forks and
calipers. I tried to explain better the rationale behind this approach
in response to Tim.

--
Fact of life #15: Heads bleed, walls don't.

[[email protected]]

Maki Tartamillo writes:

>> Why is this so difficult to comprehend?

> It isn't difficult at all and I don't disagree on James
> theory. Where did I say that? I proposed a closed dropout, did you
> read it?

And did you read the explanation why that is still not a solution? As
long as this is a QR hub without conical "lug nuts" the axle will move
in the dropout and compromise the adjustment of the clamping force.
To get a better feel for these motions consider the pedal attachment
in the cranks. In spite of being tightened so tight that one can
sense the smell of onions (tears in the eyes), pedals always move.
That is why we have left hand threads on left pedals and why there is
always a large worn fretting ring on the face of the crank. The only
thing that will prevent this, as automotive people discovered in the
1930's is to use a conical lug nut, something that is long overdo on
pedal faces... the next subject that we need to bring to the attention
of the bicycle industry after disk brake caliper positioning.

> We discussed this before, do you remember? Calipers are there
> because handling is better in this way. Also, calipers ahead of the
> fork will pull the fork instead of pushing it. Years of motorcycle
> experience shows that most people is uncomfortable with that, no
> matter how hard you try to convince them that the fork is solid
> enough.

Both of the effects you mention are urban legend. If you want to make
these points, you'll need to explain the mechanical difference between
a caliper ahead or behind the fork and how this has any effect on
handling or braking. It isn't so! We don't need to transplant M/C
urban legends into bicycling. We already have more than we need.

> The problem *is* the QR. Is sucks. It was designed for road bikes.
> Todays MTB's have extremely high performance, that means higher stresses.

You speak like a real MTB'er who believes that the MTB is a motorcycle
and necessarily flies off great jumps onto the rocks. Even the best
dirt M/C's can be destroyed with such antics. In fact road QR's are
adequate. What can break is the axle. That you can pull a wheel out
with enough force is also true but such forces do not come from riding
but from a misplaced brake caliper. The retention force of the QR
needs to be only a small fraction of the upwards forces, in fact only
enough to keep the wheel from falling out from gravitational loads and
lateral torque loads that cannot get large because spoked wheels
collapse long before axle disengagement forces are high enough to
dislodge the wheel.

> The fact that high-end freeride forks and all DH ones use different
> systems proves that, brakes apart, the standard QR's are weak.
> If you change the caliper position the QR is still weak.
> If you change the dropout direction the QR is still weak.
> The QR *needs* to be made stronger. I'm sure that not only the braking
> reaction, but general vibrations, bumps, torsion and thermal stresses
> have a role in loosening QR's. Did I say that the QR is weak and sucks?

If you use the QR's that you mention, they will still be a hazard with
a rear mounted caliper so there is no gain in your solution. What I
have asked before is why do people make these argument unless they
are defending their own product or identify with the choice of bicycle
they have mad to a degree that exceeds logic. "Hey, I bought this
bike so it's got to be good!" We see that with car buffs all the
time. So what's your angle in belittling the only effective solution
to the disk brake problem?

> What I did want to say (and sorry if I'm not always clear, but
> English is not my mother tongue especially in technical field) is
> that if we have to redesign forks and calipers, that are an order of
> magnitude more expensive than an hub, then it makes a lot of sense
> to redesign everything, starting from the real weak link, that is
> the QR. It make no sense to throw away half a bicycle to save the
> silliest and cheapest part of it.

This is also an empty argument because the solution will require a
major design change no matter hoe ineffective the one chosen is.
Therefore, moving the caliper to the front and changing nothing else
is the easiest and lest expensive solution, besides being the only
effective one I have seen.

> The motorcycle style hub with closed dropout that I suggested and you
> didn't read isn't a kludge, but a perfectly safe (and already working on
> motorcycles) solution that can be easily done with a little modify to
> the fork and without touching the calipers. Then the same modified wheel
> can be used *also* on existing forks: if they have lawyer lips it will
> provide a sensible increment in safety, especially if threadlocking
> devices are used. Not the best, but better than nothing. If you have any
> criticism to this solution please tell. But don't say "it's a kludge",
> tell me *why* it is.

Because it requires a large wrench and great force. The motorcycle
coincidentally has a large enough axle, due to its greater weight, to
permit using such a large nut. The bicycle does not and any such
massive change is not going to be taken 'lightly' by the market. This
nut should be a tapered face nut like a wheel lug nut of a car to be
truly safe. Thread locking compounds have their place but this is not
one of them.

Jobst Brandt

Palo Alto CA

[A Muzi]

> Rick Onanian writes:
> >> I'm not sure what you are envisioning. You would then have to flex
> >> the fork legs outward to fit the axle, and most forks are too stiff
> >> to be flexed easily by that amount.

> > No, you'd just pull the skewer right out of the wheel.


> wrote in message
...
> When you propose that, I take it you are not capturing the axle in the
> dropout, as is customary with a QR, but are expecting the QR to hold
> the wheel alone. In that case, the skewer would need to be about 10mm
> in diameter as axles are now. What sort of axle for mounting
> bearings, do you have in mind? I see these various suggestions as
> incomplete designs and not practical solutions.

> >> This doesn't solve the problem anyway. There will be some play
> >> when the axle is fit into its hole. It would still get pushed up
> >> and down to the extent of that play by braking and bump forces.
> >> The play wouldn't result in wheel ejection, but it still isn't good
> >> design.

[RO]> > Well, I'm no engineer, but an engineer could probably come up with
> > something like my idea but better. Or, just make the dropout holes
> > the same size as the hole in the hub -- the hub doesn't have any
> > play up and down on the skewer.

[JB]> If you are not an engineer then you probably should consider axles in
> holes without clearance a press fit and after some use a loose fit.
> Since I cannot visualize what you have in mind, I suspect your method
> has not yet been thought out to practical completion.

Well, just thinking aloud, I can imagine a system with a hole not a slot at
the end of a fork and a sleeve that is stepped to fit a large fork hole and
capture the 10mm axle end. That way you wouldn't have to spring the fork so
far apart. That sleeve would be slipped from the outside through the fork
and over the axle ends, then a skewer through all.. A positive lock ( some
variant of a castellated nut?) of some type could be used on the skewer
itself since the movement would be less, and less critical.
Obvioosly I haven't even drawn such a thing but the idea is that a closed
opening for the axle is desirable. I'm thinking along those lines because
right now the caliper is forced against the fork but reversing it would put
the caliper's mounting fasteners in tension which may introduce another set
of problems.

We all agree the present setup is not ideal. Simply moving the calipr to the
front strikes me as inviting trouble as the installation fasteners become
critical. I am not arguing that a sleeve through a pireced fork end is a
solution , just that some such approach might be workable.

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

[[email protected]]

Andrew Muzi writes:

> We all agree the present setup is not ideal. Simply moving the
> caliper to the front strikes me as inviting trouble as the
> installation fasteners become critical. I am not arguing that a
> sleeve through a pierced fork end is a solution, just that some such
> approach might be workable.

The fasteners (bolts) currently retain caliper forces no differently
than if the caliper were in any other position. They hold the caliper
against its mounting bracket against motion with friction and
ultimately bolt shear at he limit if the bolts were loose enough to
allow slip, regardless of where the caliper is positioned.

Whom are we trying to protect by not moving the caliper to where it
should be? All these other solutions require at least as much change
as repositioning the caliper.

Jobst Brandt

Palo Alto CA

[Maki]

In article >,
wrote:

> Maki Tartamillo writes:

"Maki Tartamillo" is not my name, nor my nickname, nor my email. Please
stop transfiguring names.

> >> Why is this so difficult to comprehend?
>
> > It isn't difficult at all and I don't disagree on James
> > theory. Where did I say that? I proposed a closed dropout, did you
> > read it?
>
> And did you read the explanation why that is still not a solution? As
> long as this is a QR hub without conical "lug nuts" the axle will move
> in the dropout and compromise the adjustment of the clamping force.

I think I've been the first one to point out that changing the dropout
angle would not work, so I have very clear in my mind that as long as
there is clearance the axle *can* move. But you should remember that we
are talking of extreme cases, most people is using disk brakes as they
are without problems. In those extreme cases, with a closed dropout the
wheel is not going to be ejected so, in that sense, is safe. You will
notice the wheel is loose and tighteen it.
Personally I believe that solutions like QR20 or Tullio should be the
standard, but since it is too expensive to convert all the existing
forks I suggested a compromise. Being a compromise it cannot be optimal
under all points of view.

> > We discussed this before, do you remember? Calipers are there
> > because handling is better in this way. Also, calipers ahead of the
> > fork will pull the fork instead of pushing it. Years of motorcycle
> > experience shows that most people is uncomfortable with that, no
> > matter how hard you try to convince them that the fork is solid
> > enough.
>
> Both of the effects you mention are urban legend. If you want to make
> these points, you'll need to explain the mechanical difference between
> a caliper ahead or behind the fork and how this has any effect on
> handling or braking. It isn't so! We don't need to transplant M/C
> urban legends into bicycling. We already have more than we need.

You answered the post of "A Muzi". Most people reason like that.
Actually, pushing has better load spreading than pulling, but with
proper sizing you can work around it. As said it is a psycological thing.
For the handling part I already explained it too but I'll redo it for
you: the closer the caliper is to the steering center line the lower is
its inertia when you turn the handelebar. How much it is noticable is
open to debate, but the mechanic principle is there. MX motorcycles
started with the calipers in front but soon changed. Maybe they all are
not a bunch of losers?

> > The problem *is* the QR. Is sucks. It was designed for road bikes.
> > Todays MTB's have extremely high performance, that means higher stresses.
>
> You speak like a real MTB'er who believes that the MTB is a motorcycle
> and necessarily flies off great jumps onto the rocks. Even the best

Oh! And I tought that disk brakes are used by mommies to reach the mall.
Go figure...
Have you ever seen a mountain bike in action? And a motorcycle?
It's not that flying off great jumps is the norm for everybody, but nor
it is braking at 0,6g.
How do you explain the fact that every manufacturer sells alternative
solutions for locking the front wheel? Maybe someone found that the
standard QR isn't all that stiff?

> If you use the QR's that you mention, they will still be a hazard with
> a rear mounted caliper so there is no gain in your solution. What I
> have asked before is why do people make these argument unless they
> are defending their own product or identify with the choice of bicycle
> they have mad to a degree that exceeds logic. "Hey, I bought this
> bike so it's got to be good!" We see that with car buffs all the
> time. So what's your angle in belittling the only effective solution
> to the disk brake problem?

What's yours?
I don't work in the bicycle industry, I've nothing to defend, I don't
use disk brakes on bicycles and I'm not belittling anyone or anything.
I'm sharing my ideas in the spirit of Usenet. If I find a fault in your
reasoning I tell you, if you find a fault in mine you tell me. At the
end we are both richer. If you don't believe that I don't know why you
are wasting your time on Usenet.

> This is also an empty argument because the solution will require a
> major design change no matter hoe ineffective the one chosen is.
> Therefore, moving the caliper to the front and changing nothing else
> is the easiest and lest expensive solution, besides being the only
> effective one I have seen.

Changing noting else??? The only part that you save is a 5$ QR!!!
It's two days that I'm trying to communicate with you but either I'm not
able to express myself or you are not able/willing to understand. I'll
repeat once more, then I'll give up.
I have two objections to your solution:

a) it costs too much for the industry to recall every existing fork. It
is far cheper to defend themselves in the court and show the users are
sloppy. If you can convince Mr Rockshox to give me a new fork for free
I'm happy, but I'm not holding my breath. From James' page:
|James, it seems that, at least in the US 'operator error' has been the
|prominent call from the legal world.
That's Rockshox speaking. Do you really believe they will do it?

b) I'm not sure your solution is complete. What's sure is that it will
nullify the braking force reaction, which is important. However we still
have the wimpy QR. So far we have always talked about the disengaging
force, but that's only the most evident phenomenon. What about torsion?
When you brake you generate a couple that twists (not sure this is the
correct term, but you get the idea) the left leg. When it is twisted the
two dropouts are no longer aligned and this means that either the axle
bends or the QR and nut may slip (depending on the amount of torsion).
Since the axle is not firmly hold by the dropout my guess is that the QR
can easily slip. Of course this has to be verified in practice, but I'm
pretty confident that the effect of cyclic fork torsion has similar
effects to that of the disengaging force. We'll still end up with an
unscrewing effect.
Since your solution in any case requires to rebuild the fork (and most
likely the calipers) I can't see a reason not to rebuild the hub/fork
too and get rid of all those worries. The solutions already exist, and
their only, common, fault is that they are all proprietary. IMHO
manufacturers should meet and came out with a new system that finally
works, without "but" and "if". That's a bolt-through design.

> > devices are used. Not the best, but better than nothing. If you have any
> > criticism to this solution please tell. But don't say "it's a kludge",
> > tell me *why* it is.
>
> Because it requires a large wrench and great force. The motorcycle
> coincidentally has a large enough axle, due to its greater weight, to
> permit using such a large nut. The bicycle does not and any such
> massive change is not going to be taken 'lightly' by the market. This

It will still allow more tension than a conventional QR. Or not?

> nut should be a tapered face nut like a wheel lug nut of a car to be
> truly safe. Thread locking compounds have their place but this is not
> one of them.

So you aren't reading me... "Thread locking compounds"... whoever talked
about that? I'm speaking of a QR that enters the dropout slot so that it
cannot turn once close. It's easy to do. It's less easy on the nut side,
but it can be done. And in any case it should be almost unnecessary
since according to James' theory the force on the nut is really low.

--
Fact of life #15: Heads bleed, walls don't.

[Maki]

In article >,
Maki > wrote:

> b) I'm not sure your solution is complete. What's sure is that it will
> nullify the braking force reaction, which is important. However we still
> have the wimpy QR. So far we have always talked about the disengaging
> force, but that's only the most evident phenomenon. What about torsion?
> When you brake you generate a couple that twists (not sure this is the
> correct term, but you get the idea) the left leg. When it is twisted the
> two dropouts are no longer aligned and this means that either the axle
> bends or the QR and nut may slip (depending on the amount of torsion).
> Since the axle is not firmly hold by the dropout my guess is that the QR
> can easily slip. Of course this has to be verified in practice, but I'm
> pretty confident that the effect of cyclic fork torsion has similar
> effects to that of the disengaging force. We'll still end up with an
> unscrewing effect.

Forgot to add...
| There are three common causes of the relative motion occurring in the
| threads:
|
|1. Bending of parts which results in forces being induced at the
|friction surface. If slip occurs, the head and threads will slip which
|can lead to loosening.
|
|2. Differential thermal effects caused as a result of either
|differences in temperature or differences in clamped materials.
|
|3. Applied forces on the joint can lead to shifting of the joint
|surfaces leading to bolt loosening.

This is from James' page, quoting
<http://www.boltscience.com/pages/vibloose.htm>
I'm specifically referring to point 1. Since disk brakes generate an
insane amount of heat point 2 is a cause of serious concern too.

--
Fact of life #15: Heads bleed, walls don't.

[James Annan]

Maki wrote:

> |James, it seems that, at least in the US 'operator error' has been the
> |prominent call from the legal world.
> That's Rockshox speaking. Do you really believe they will do it?

Do you really believe that ultimately they will have a choice? Just
because they have money, does not mean that they can prove black is
white, even in a US court. IMO a few unequivocal statements from
independent testing labs (such as the German one that is investigating
the problem) will put intolerable pressure on them. At some point they
may have to start worrying about the unlimited punitive damages rather
than merely compensation - this is the fault with the 'cheaper to
compensate' line of thought.

The manufacturers might be able to pull the wool over the eyes of the
CPSC for some time, but not indefinitely. Those guys also have a duty to
investigate and have their own reputation to worry about if they miss
such glaring fault as this.

Not sure about the USA law, but in the UK, the level of proof required
is 'on the balance of probabilities' not 'beyond reasonable doubt'. IMO
we are already well beyond this lower threshold for many of the failures
I have heard about.

James

[[email protected]]

Maki Tartamillo writes:

>>> It isn't difficult at all and I don't disagree on James theory.
>>> Where did I say that? I proposed a closed dropout, did you read
>>> it?

It isn't a "theory." It is a straight forward measurable fact and is
obvious by inspection, geometrically knowing that forces have actions
and reactions. The way you say that, I detect skepticism. You don't
disagree with... sounds like the reassuring, "some of them are my best
friends."

>> And did you read the explanation why that is still not a solution?
>> As long as this is a QR hub without conical "lug nuts" the axle
>> will move in the dropout and compromise the adjustment of the
>> clamping force.

> I think I've been the first one to point out that changing the
> dropout angle would not work, so I have very clear in my mind that
> as long as there is clearance the axle *can* move. But you should
> remember that we are talking of extreme cases, most people is using
> disk brakes as they are without problems. In those extreme cases,
> with a closed dropout the wheel is not going to be ejected so, in
> that sense, is safe. You will notice the wheel is loose and
> tighten it.

We are not talking about "extreme cases" but rather reasonably
predictable failures among normal distributions of users. Why wheels
do not separate more often has been explained. The greatest number of
riders assemble their bicycles after arriving by car at the trailhead.
This assures a tight QR at the beginning of each ride. Of those that
do not do that, only a small number experience any loosening and don't
question that the wheel was rattling in the retention ridges and
tighten it. This is not a reasonable way to offer a product to users.

> Personally I believe that solutions like QR20 or Tullio should be
> the standard, but since it is too expensive to convert all the
> existing forks I suggested a compromise. Being a compromise it
> cannot be optimal under all points of view.

In other words, you would not fix the problem but just use "a bigger
hammer" as it is often referred to.

>>> We discussed this before, do you remember? Calipers are there
>>> because handling is better in this way. Also, calipers ahead of
>>> the fork will pull the fork instead of pushing it. Years of
>>> motorcycle experience shows that most people is uncomfortable with
>>> that, no matter how hard you try to convince them that the fork is
>>> solid enough.

>> Both of the effects you mention are urban legend. If you want to make
>> these points, you'll need to explain the mechanical difference between
>> a caliper ahead or behind the fork and how this has any effect on
>> handling or braking. It isn't so! We don't need to transplant M/C
>> urban legends into bicycling. We already have more than we need.

> You answered the post of "A Muzi". Most people reason like that.
> Actually, pushing has better load spreading than pulling, but with
> proper sizing you can work around it. As said it is a psychological thing.
> For the handling part I already explained it too but I'll redo it for
> you: the closer the caliper is to the steering center line the lower is
> its inertia when you turn the handlebar. How much it is noticeable is
> open to debate, but the mechanic principle is there. MX motorcycles
> started with the calipers in front but soon changed. Maybe they all are
> not a bunch of losers?

>>> The problem *is* the QR. Is sucks. It was designed for road
>>> bikes. Todays MTB's have extremely high performance, that means
>>> higher stresses.

>> You speak like a real MTB'er who believes that the MTB is a
>> motorcycle and necessarily flies off great jumps onto the rocks.
>> Even the best

> Oh! And I thought that disk brakes are used by mommies to reach the mall.
> Go figure...

> Have you ever seen a mountain bike in action? And a motorcycle?
> It's not that flying off great jumps is the norm for everybody, but
> nor it is braking at 0,6g.

> How do you explain the fact that every manufacturer sells alternative
> solutions for locking the front wheel? Maybe someone found that the
> standard QR isn't all that stiff?

Some are patented and others are less expensive or have a lighter
closure handle than others. These folks work hard to differentiate
themselves from competitors. Just read their claims.

>> If you use the QR's that you mention, they will still be a hazard
>> with a rear mounted caliper so there is no gain in your solution.
>> What I have asked before is why do people make these argument
>> unless they are defending their own product or identify with the
>> choice of bicycle they have mad to a degree that exceeds logic.
>> "Hey, I bought this bike so it's got to be good!" We see that with
>> car buffs all the time. So what's your angle in belittling the
>> only effective solution to the disk brake problem?

> What's yours?

> I don't work in the bicycle industry, I've nothing to defend, I
> don't use disk brakes on bicycles and I'm not belittling anyone or
> anything. I'm sharing my ideas in the spirit of Usenet. If I find
> a fault in your reasoning I tell you, if you find a fault in mine
> you tell me. At the end we are both richer. If you don't believe
> that I don't know why you are wasting your time on Usenet.

Let me say it more succinctly. Why do you oppose moving the caliper
to the front of the fork, placed exactly the same as it is now but the
fork leg rotated 180 degrees... with any asymmetrical fork features
remaining where they are?

>> This is also an empty argument because the solution will require a
>> major design change no matter hoe ineffective the one chosen is.
>> Therefore, moving the caliper to the front and changing nothing
>> else is the easiest and lest expensive solution, besides being the
>> only effective one I have seen.

> Changing noting else??? The only part that you save is a 5$ QR!!!
> It's two days that I'm trying to communicate with you but either I'm not
> able to express myself or you are not able/willing to understand. I'll
> repeat once more, then I'll give up.

Your solution requires re-tooling the fork and if a new casting must be
made then changing the brake bracket is no problem. In any case, old
forks cannot be modified to meet the problem for the future.

> I have two objections to your solution:

> a) it costs too much for the industry to recall every existing fork.
> It is far cheaper to defend themselves in the court and show the
> users are sloppy. If you can convince Mr Rockshox to give me a new
> fork for free I'm happy, but I'm not holding my breath. From James'
> page:

> |James, it seems that, at least in the US 'operator error' has been
> |the prominent call from the legal world.

> That's Rockshox speaking. Do you really believe they will do

> b) I'm not sure your solution is complete. What's sure is that it
> will nullify the braking force reaction, which is important.
> However we still have the wimpy QR. So far we have always talked
> about the disengaging force, but that's only the most evident
> phenomenon. What about torsion? When you brake you generate a
> couple that twists (not sure this is the correct term, but you get
> the idea) the left leg. When it is twisted the two dropouts are no
> longer aligned and this means that either the axle bends or the QR
> and nut may slip (depending on the amount of torsion). Since the
> axle is not firmly hold by the dropout my guess is that the QR can
> easily slip. Of course this has to be verified in practice, but I'm
> pretty confident that the effect of cyclic fork torsion has similar
> effects to that of the disengaging force. We'll still end up with
> an unscrewing effect.

As you see, forks are now made as a single unit casting connected with
an ever stronger bridge because one sided brake attachment causes
differential fork leg displacement. They are working on it and will
continue to do so. I don't think we should expect a disclosure of
what is next or how the industry believes it is liable.

> Since your solution in any case requires to rebuild the fork (and
> most likely the calipers) I can't see a reason not to rebuild the
> hub/fork too and get rid of all those worries. The solutions
> already exist, and their only, common, fault is that they are all
> proprietary. IMHO manufacturers should meet and came out with a new
> system that finally works, without "but" and "if". That's a
> bolt-through design.

I don't understand what you mean by this. Do you now propose that
the caliper be moved to the front along with your skewer proposal?

If MTB users are agreeable with no QR for their wheels, that would not
be a problem but I doubt that riders want to give up the ability to
take a wheel out and change a tube or tire without tools on the trail.

>>> devices are used. Not the best, but better than nothing. If you
>>> have any criticism to this solution please tell. But don't say
>>> "it's a kludge", tell me *why* it is.

I don't have a sufficiently clear picture of your design to analyze
its faults but a 20mm diameter closed dropout has problems. I don't
see how it is held and secured.

>> Because it requires a large wrench and great force. The motorcycle
>> coincidentally has a large enough axle, due to its greater weight, to
>> permit using such a large nut. The bicycle does not and any such
>> massive change is not going to be taken 'lightly' by the market. This

> It will still allow more tension than a conventional QR. Or not?

No doubt. A larger screw can exert larger force.

>> nut should be a tapered face nut like a wheel lug nut of a car to be
>> truly safe. Thread locking compounds have their place but this is not
>> one of them.

> So you aren't reading me... "Thread locking compounds"... whoever talked
> about that? I'm speaking of a QR that enters the dropout slot so that it
> cannot turn once close. It's easy to do. It's less easy on the nut side,
> but it can be done. And in any case it should be almost unnecessary
> since according to James' theory the force on the nut is really low.

There you go again calling a theory. These are all hard facts.

Jobst Brandt

Palo Alto CA

[Fakhina Sohl]

wrote in message >...
> It isn't a "theory." It is a straight forward measurable fact and is
> obvious by inspection, geometrically knowing that forces have actions
> and reactions.

Let's not forget that Newtonian physics is only a theory...

Seriously though, here's my A$0.03. The two sides of this argument are
proposing, respectively, redesigning the system to be infallible under
design loads, and redesigning the system to fail safely.

I am very much in favour of the second approach - especially as a
first-response solution.

Especially on a mountain bike, "design loads" mean nothing. People
will, and do, ride to the limits of their equipment.

Even if we only consider manufacturing variability, there _will_ be
failures in the field. It's a statistical certainty. Whether the QR
skewers are as thick as your finger and located in recessed conical
seats as Jobst proposes...there will be a defective part, and it will
fail.

WHEN that one-in-a-billion part fails, if the caliper is behind a
vertical dropout, the axle WILL tend to be ejected under brakes. It is
an unacceptable failure mode.

The system needs to be re-designed so that if/when an axle slips,
breaks, whatever, the wheel will not be ejected by braking forces.
That means either re-directing the force (eg. caliper in front of fork
leg) or providing support for the force as it is currently directed
(eg. forward-facing dropouts, QR20/Tullio closed retention systems).

I can only imagine one direction from here. Fork/brake manufacturers
can't afford the legal implications of admitting that there's a
problem. The lawsuits would break them. But the next design iteration
of all fork models will either have closed retention systems, or no
disc brake mounts.

The reason given will be that the XC race forks are so light and
cutting-edge that they can't handle disc brake loads without
compromising performance; and the
freeride/all-mountain/whatever-the-buzzword-is-this-week will be all
Tullio or QR20 for increased stiffness.

Dropout forks with disc brake mounts will be quietly dropped from the
lineup. The axle-eject issue will be sidestepped.

In any case, my next bike will have discs and clamped axles. I've just
started using discs on my current dropout fork - mindful of the
shortcomings in the design. I'd like it to be otherwise, but it's not
going to happen with my budget.

fs

[Dion Dock]

In my experience, the QR is much easier to undo at the end of a long ride.
(Yes, this is on a bike with a front disc brake.) When I first noticed
this, I assumed it was because they were off-brand skewers.

I have yet to find the QR completely loose, but it definitely takes less
effort to open it than to close it.

-Dion

> wrote in message
...

> We are not talking about "extreme cases" but rather reasonably
> predictable failures among normal distributions of users. Why wheels
> do not separate more often has been explained. The greatest number of
> riders assemble their bicycles after arriving by car at the trailhead.
> This assures a tight QR at the beginning of each ride. Of those that
> do not do that, only a small number experience any loosening and don't
> question that the wheel was rattling in the retention ridges and
> tighten it. This is not a reasonable way to offer a product to users.
CA

[Maki]

In article >,
James Annan > wrote:

> > |James, it seems that, at least in the US 'operator error' has been the
> > |prominent call from the legal world.
> > That's Rockshox speaking. Do you really believe they will do it?

> Do you really believe that ultimately they will have a choice? Just

I'm not sure they can *afford* it. It is true that a lot of forks are
sold as OEM parts so they can refuse to recall them unless the bike
mounted disks right out of the factory, but there's still a hell of a
lot of forks to update. And they have to pay for labour too, not only
the parts that for them may be relatively cheap to produce.
Popular pressure (i.e. people refusing to buy disk brakes, but I don't
see it happen) can lead them to use better solutions in the future, but
I'm not optimistic about existing stuff.
I hope I'm wrong, but I think the scenario painted by Fakhina Sohl is
the more realistic I've seen.

> because they have money, does not mean that they can prove black is
> white, even in a US court. IMO a few unequivocal statements from
> independent testing labs (such as the German one that is investigating
> the problem) will put intolerable pressure on them. At some point they
> may have to start worrying about the unlimited punitive damages rather
> than merely compensation - this is the fault with the 'cheaper to
> compensate' line of thought.

Read Pace arguments to see their defense line. For them it's always
someone else's fault, their product is ISO compliant.

--
Fact of life #15: Heads bleed, walls don't.

[Maki]

In article >,
Rick Onanian > wrote:

> > Why are you still calling me that way? You look really childish.
>
> Somehow, I get the idea that he's not sitting there typing
> out "Maki Tartamillo writes:" on his keyboard.

Unfortunately he probably does since it doesn't happen with other people.
Or at least he changed the settings in his newsreader so that it does
the job for him. That's not the default for Tin, which is, I'm told, an
excellent newsreder.

--
Fact of life #15: Heads bleed, walls don't.

[Rick Onanian]

On Fri, 15 Aug 2003 19:29:02 GMT, Maki > wrote:
> In article >,
> Rick Onanian > wrote:
>> Somehow, I get the idea that he's not sitting there typing
>> out "Maki Tartamillo writes:" on his keyboard.
>
> Unfortunately he probably does since it doesn't happen with other people.
> Or at least he changed the settings in his newsreader so that it does the
> job for him. That's not the default for Tin, which is, I'm told, an
> excellent newsreder.

Tin is a very excellent newsreader, but can come
in a very wide variety of configurations. It's
nowhere near unreasonable to expect that the
default configuration that he has will do that.

Granted, it is possible that he has changed the
settings himself; this may have been to alleviate
some other problem.

I just don't believe that _anybody_ would make an
effort to type out "So and so writes..."; and
I especially don't believe that anybody would do
that _and_ continuously do it wrong.

Gah. I find myself in the middle of somebody else's
argument again. Now I'm even _guessing_ what other
people are doing and thinking! When will I learn? ;)

Jobst? Care to comment?
--
Rick Onanian