More on disk brakes and wheel ejection

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": geocities.comczcornerOpen ↗

Tim McNamara said:

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 [email hidden] Palo Alto CA

<[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Tim McNamara said:

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

John Rees said:

Quoted message said:

Quoted message said:

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.

Quoted message said:

Quoted message said:

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.

Quoted message said:

Quoted message said:

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.

Quoted message said:

Quoted message said:

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

Quoted message said:

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 [email hidden] Palo Alto CA

Quoted message said:

<[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

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.

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

<[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

John Rees said:

Quoted message said:

> 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.

Quoted message said:

Quoted message said:

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.

Quoted message said:

Quoted message said:

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.

Quoted message said:

Quoted message said:

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

Quoted message said:

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..

Quoted message said:

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.

Think about it. Why does the motion only LOOSEN the QR thread? If it was random, and just up and
down movement, why doesn't it sometimes also TIGHTEN the QR? Putting the skewer in from the other
side does not reverse the threads. I agree the skewers are not up to the stress imposed by a disk on
the suspension fork. I'm also not convinced that moving the calliper to the fork front is going to
completely solve the problem. Why not also make the front dropout horizontal, rear entry?

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?

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

John Rees

[email hidden] wrote in message news:<[email hidden]>...

Quoted message said:

Tim McNamara said:

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.

Quoted message said:

A free body diagram

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

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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

anonymous snipes rudely from cover:

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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

Quoted message said:

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.

Quoted message said:

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 [email hidden] Palo Alto CA

Sheldon Brown said:

Quoted message said:

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.

Quoted message said:

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

Quoted message said:

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.

Quoted message said:

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 [email hidden] Palo Alto CA

John Rees said:

Quoted message said:

Quoted message said:

> 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.

Quoted message said:

Quoted message said:

Quoted message said:

> 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.

Quoted message said:

Quoted message said:

Quoted message said:

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

Quoted message said:

Quoted message said:

Quoted message said:

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?

Quoted message said:

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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 on cars that open to the rear
and many other things that have shown their worth pragmatically over millions of vehicles. Maybe we
should revive the air cooled car engine, solid axles and king pin steering again.

I'm sure you should think about it!

Jobst Brandt [email hidden] Palo Alto CA

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

Quoted message said:

Quoted message said:

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>

Quoted message said:

Jobst Brandt [email hidden] Palo Alto CA

--
Rick Onanian

Rick Onanian said:

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

<[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

John Rees said:

Quoted message said:

>> I disagree. A free body diagram shows that forces from a "rear

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.

Sigh. I see that your tone is different for different people. I guess it's also my newsreaders fault
that I see duplicate posts from you only and no other person? I did not realise this had been a long
running thread, and it's not my fault that I didn't see the first 1k posts about it. Neither you nor
I 'own' the thread. You're more willing to agree with Sheldon Brown, who has more personality in his
thumbnail than you appear to have in your entire body, than you are with
me. Even though his suggestions are similar to (and quite likely much better than) mine.

Quoted message said:

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.

Quoted message said:

Why even have a dropout? Since there isn't a yellow motorcycle chasing

XC

Quoted message said:

Quoted message said:

riders around in races to make quick wheel changes, why is there a need

for

Quoted message said:

Quoted message said:

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.

You have made an incorrect assumption my smug tongued expert. I ride plenty enough and own plenty of
bikes. And if you're ever in NC, why don't you join us for a ride and we will be happy to drop you
on our beautiful rolling hills. I never said anything about a wrench. My point is if there is
concern that the current popular design causes wheels to be shed, then the current design needs to
be re-thought. And, if you are not open minded enough to considers another's ideas, then it only
reinforces the smug label you have earned with
mf.

Quoted message said:

Quoted message said:

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.

Yes. Please consider why it would be a big deal for it to take an extra 30 seconds to remove a front
wheel from a disc braked bike. The only issue I can think of where having a different mounting
system for disc wheels is that maybe it would be a hassle to swap wheels between disc and non disc
bikes. But we have long ago departed true compatibility in this area since many disc only wheels no
longer even HAVE braking surfaces so you already can't swap.

Quoted message said:

Quoted message said:

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.

This point would make sense if we all still rode rigid forked, lightweight mountain bikes with canti
brakes. But we don't, do we? The modern mountain bike has undoubtedly evolved significantly in the
last 20 years. An evolution that far outstrips anything that's happened to road bikes, and for that
matter automobiles. When cars evolved from their horse carriage origins, and become heavier, faster
and more powerful, wasn't there a switch from wooden wheels to pneumatic tires? Weren't the wooden
wheels well proven and pragmatic for maybe centuries? So why on earth don't we still have wooden
wheels on cars (or bikes for that matter)? You're the wheel expert, so please share with us.

Quoted message said:

I'm sure you should think about it! Jobst Brandt

Every day. John Rees

In article said:

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.

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

Sheldon Brown said:

Quoth Jobst:

Quoted message said:

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 said:

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.

Quoted message said:

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.

Quoted message said:

Stergios

--
Rick Onanian

Rick Onanian said:

Quoted message said:

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

Stergios Papadakis said:

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

Stergios

--
Rick Onanian

[email hidden] wrote in message news:<[email hidden]>...

Quoted message said:

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.

Quoted message said:

Quoted message said:

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.

Quoted message said:

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?

Quoted message said:

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

Quoted message said:

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

Quoted message said:

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.

Quoted message said:

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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