Re: x-post: Bike Biz: Wheel ejection theory goes legal



E

Ed Pirrero

Guest
On Feb 14, 11:44 am, "G.T." <[email protected]> wrote:
> Ed Pirrero wrote:
>
>
> > Science is not about faith, Greg. So, let me ask you this: is it
> > possible, even slightly, that any or all of these incidents are due to
> > user error? It's a yes/no question.

>
> Of course.


Which, since you seem to have ignored it up to this point, is my
freakin' point.


> But there's nothing I've read of yours that admits it could
> be possible, even slightly, that any or all of these incidents are due
> to poor design.


Then you have read only what you want to read, and not what I have
written. Since I do not have sufficient data to reach a conclusion of
"poor design", I'm not going to leap there. So, let me be explicit,
so you can swallow some of that bile you're spewing:

If indeed the QRs are not enough to retain the disk-braked wheel, then
the design is compromised, and needs to be changed. I do not regard
all the assumptions and anecdotes up to this point as data - not even
the ongoing experiments jim and I are doing in parallel.

This has always been my position - cranks in r.b.t. trying to assign
me a different one notwithstanding.

E.P.
 
J

Jay Beattie

Guest
On Feb 10, 12:18 pm, Gary Young <[email protected]> wrote:
> On Sat, 10 Feb 2007 11:13:08 -0800, Ed Pirrero wrote:
> > On Feb 10, 11:03 am, Gary Young <[email protected]> wrote:
> >> On Sat, 10 Feb 2007 10:43:57 -0800, Ed Pirrero wrote:
> >> > On Feb 10, 8:47 am, [email protected] wrote:
> >> >> On Feb 9, 11:18 pm, Mark Hickey <[email protected]> wrote:

>
> >> >> > I'm a "skewer skeptic" (sic) based on the following assumptions...

>
> >> >> > 1) A number of people will fail to properly tighten their skewer
> >> >> > before a given ride. This might be from inattention, or could be
> >> >> > because the skewer caught the edge of the lawyer lip or other
> >> >> > debris (preventing it from fully closing).

>
> >> >> > 2) The number of wheel ejections we've heard about (directly and
> >> >> > indirectly) are quite small.

>
> >> >> > 3) I think it's very reasonable to assume that the number of case
> >> >> > number 1 scenarios could eaily exceed the number of case number 2
> >> >> > scenarios. Ipso facto, it's not at all unreasonable to assume
> >> >> > that I've got very little to worry about when I'm riding my MTB.

>
> >> >> While all three of your points are correct, they don't make the
> >> >> problem go away.

>
> >> >> Point 1 is correct, but from the reports we've read, the problem has
> >> >> been demonstrated many times by people who almost certainly did
> >> >> fasten the QR properly.

>
> >> > Without any verification, "almost certainly" is pretty gratuitous.
> >> > Taking data from uncontrolled experiments and using it as evidence is
> >> > normally called "junk science."

>
> >> >> (If j.b. or others say _all_ those people failed to tighten
> >> >> properly, despite pre-knowledge of the problem and lots of prior
> >> >> experience, I expect they'd deny any lab test based on the same
> >> >> criterion!)

>
> >> > That's a strawman, and we both know it. Neither you nor I know the
> >> > conditions under which the QRs in those stories were tightened, and
> >> > have absolutely no clue what the initial conditions were.

>
> >> > If it were an experiment from a grad student, for publication, would
> >> > you let that slide?

>
> >> > Well, *you* might, but the publication wouldn't.

>
> >> >> Point 2 is correct, IMO, simply because the problem is limited
> >> >> almost exclusively to a single riding situation: long, bumpy
> >> >> downhills with hard braking.

>
> >> > We have such conditions out here in the Western U.S. In fact, I
> >> > would suggest that those sorts of conditions prevail in MTB country -
> >> > CO Front Range, Moab area in Utah, Arizona, CA, etc. There are LOTS
> >> > of mountain bikers in those areas, and folks who are pretty serious
> >> > about their riding.

>
> >> > And yet, the stories of loosening don't come from there, but from the
> >> > comparatively flat region of the world known as the United Kingdom.
> >> > This anomaly seems to be ignored by the pro-redesign crowd - for
> >> > reasons I cannot fathom.

>
> >> > I also ride in the West U.S. - ID, to be clear. There are a LOT of
> >> > long, steep, bumpy downhills. In fact, one of my regular rides
> >> > requires me to ride about 5 miles of wide doubletrack and fire road
> >> > so that I can ride down one mile of very bumpy, steep and twisty
> >> > singletrack. Never had any loosening.

>
> >> >> Point 3 is probably correct, since the odds are you "Point 2" type
> >> >> riding fairly infrequently - and because you've read these
> >> >> discussions, you'll be damned sure to watch for the problem!

>
> >> > This is correct. I regularly inspect my front QRs. More now, but I
> >> > did do it before I had disk brakes.

>
> >> >> Still, there are folks who will not have heard of this, who will buy
> >> >> "good" equpment, use it as directed, and put themselves at great
> >> >> risk.

>
> >> > This assumes facts not in evidence.

>
> >> >> That's a description of a faulty design.

>
> >> > Actually, MTBing starts out being kinda risky. I have known a few
> >> > folks who have broken rear triangles on their FS MTBs, and crashed as
> >> > a result. One of those guys had a broken femur, and had to be
> >> > carried 4 miles out. He was using the equipment as designed. And
> >> > yet this brand of MTB and this model is sold a lot. I suppose a
> >> > recall or redesign is in order?

>
> >> If the design could be improved at a reasonable cost, then yes, a
> >> redesign would be in order.

>
> > Because ONE guy got hurt? That's pretty knee-jerk...

>
> >> If some failure is inevitable given even the best in design, then no, a
> >> redesign would not be in order.

>
> > I think this would be the case with EVERY mechanical item. And
> > sometimes "best" is not cost-effective.

>
> Agreed. That's why I said the change should be made if it can be done at
> reasonable cost. It may be hard to quantify what's reasonable, but the law
> generally asks juries to look at what an average consumer would expect for
> his money. If informed consumers are generally willing to accept a certain
> tradeoff between cost and safety, then that's generally deemed reasonable.
> (while I think that's an accurate overview, the case at hand might be
> treated differently because the brake placement might be considered a
> design defect triggering strict liability -- I'm sure JayBeattie, if he's
> following this thread, could give a more accurate picture.) You can't just
> look at the costs to the manufacturers, because they have an interest in
> imposing their costs onto the consumer (that is, refusing to pay the price
> for externalities).
>
> One of the ways that manufacturers get away with imposing externalities on
> consumers without compensation is by failing to disclose defects. If
> consumers don't know about a defect, they are likely to chalk up failures
> to other factors -- user error, unavoidable fatigue, etc.
>
> To me, that means that at the very least manufacturers should be required
> to disclose this problem to their consumers. Suppose, for instance, that
> fork makers were required to include with their forks and in
> advertisements the following message:
>
> Dear consumer:
> Applying your front disk brake creates a force that tends to eject the
> wheel from the dropouts. Our research leads us to believe that this is not
> a problem in practice if you use your quick release in the proper fashion.
> Please follow carefully our instructions regarding quick releases.
>
> What would be your objections to that? I know why manufacturers would fear
> that, though they might not say it out loud -- a lot of consumers would be
> leery of buying a fork from someone boneheaded enough to place the brake
> in a way that tends to eject the wheel.
>
> >> After all, if it's possible to get hurt, a> redesign is

> necessary,
> >> right?

>
> >> No one is saying anything that silly.

>
> > Actually, they are. AFAIK, there are zero proven disk-ejection
> > injuries. There have been a lot of assumptions made, but very little
> > proof.

>
> So we have to wait for someone to get killed or seriously injured before
> we take action? Why? Why not no killings or serious injuries from this
> cause?
>
> Given what you've said above, one indisputable case still wouldn't be
> enough for you: "Because ONE guy got hurt? That's pretty knee-jerk..."
> How many bodies have to pile up before you'd think action is necessary?
>
>
>
> > And yet, on the basis of assumption, and no real data, people are crying
> > for a redesign. Because of the possibility that someone might get hurt,
> > when all the assumptions line up in a specific way.

>
> > E.P.- Hide quoted text -

>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -



I've been busy doing the dirty-work of evil manufacturers, so I
haven't followed along much. Anyway, under a strict "consumer
expectation" test, a bicycle or component manufacturer is subject to
liability if a design or manufacturing defect makes a product more
dangerous than expected by a reasonable consumer -- this is the so-
called "consumer expectation" test. So, if a reasonable consumer
does not expect his/her front wheel to be ejected by braking forces,
and the wheel does eject, then the wheel/brake/bike (whatever part is
the culprit) is dangerously defective, and the manufacturer is subject
to liability (with the usual comparative fault/misuse/modification
defenses).

California came up with a "risk-utility test" to supplement the
consumer expectation test maybe 40 years ago to deal with products
that were obviously dangerous (and were expected to cause injury) or
which were so complicated that no consumer had an expectation
concerning safety. Cigarettes, for example, are not unreasonably
dangerous under the consumer expectation test because everyone knows
they will kill you. They flunk the risk-utility test, though because
they have no utility. You don't even need to use the risk-utility
test with front brakes, though, since they are not obviously dangerous
and we do not expect them to eject the front wheel. All you need to
do is tie the ejection to a "defect" (the placement of the caliper)
and not to some schmuck failing to tighten a quick release.

I represent some big bicycle manufacturers and have not seen a disc
brake wheel ejection case in Oregon. In fact, I wish they would
start ejecting so I could get some more bicycle work. Anyone in
Oregon who is considering getting injured, please do so in the Bend
are during winter so I can work in some skiing on Batchelor. Nobody
should get injured in Lakeview, ever, since it is a gawdawful long
drive through endless scrub. Thank you. -- Jay Beattie.
 
On Feb 14, 1:26 pm, Ben C <[email protected]> wrote:
> On 2007-02-14, [email protected] <[email protected]> wrote:
>
> > On Feb 14, 3:48 am, Ben C <[email protected]> wrote:

> [...]
> >> The point is that wheel ejection is a molehill of similar proportions.

>
> > If you want to prove the front-mount-fatigue issue is of similar
> > importance to the bike wheel ejection issue, it should be easy for you
> > to do so. Just post here the tales of motorcycles losing their front
> > mount calipers due to fatigue.

>
> If no such tales can be found that just proves that the motorcycle
> designers made sufficiently strong or fatigue-resistant caliper mounts
> to overcome the problem. I would expect the likes of Honda to get that
> right whatever the basic design. It doesn't tell us anything about the
> relative importances of fatigue and ejection.


It doesn't take "the likes of Honda" to get that feature right. The
problem is simple enough that sophomore students in mechanical design
can get it right easily, and without the need for any sophisticated
FEA software.

I think you're overly impressed with the idea of tensile fatigue, and
don't realize how routine it is to design components that successfully
handle it.

Look at your front brake's caliper arms again. They undergo a tensile
fatigue cycle each time you apply your brakes, due to bending
stresses. Have you ever had a caliper arm fatigue? Have you ever
seen one that did fatigue? Have you ever heard a tale of a person
injured, or nearly injured, because of such a thing?

That particular molehill is microscopic.

- Frank Krygowski
 
T

Tim McNamara

Guest
In article <[email protected]>,
Ben C <[email protected]> wrote:

> On 2007-02-14, [email protected] <[email protected]> wrote:
> > On Feb 14, 3:48 am, Ben C <[email protected]> wrote:

> [...]
> >> The point is that wheel ejection is a molehill of similar
> >> proportions.

> >
> > If you want to prove the front-mount-fatigue issue is of similar
> > importance to the bike wheel ejection issue, it should be easy for
> > you to do so. Just post here the tales of motorcycles losing their
> > front mount calipers due to fatigue.

>
> If no such tales can be found that just proves that the motorcycle
> designers made sufficiently strong or fatigue-resistant caliper
> mounts to overcome the problem. I would expect the likes of Honda to
> get that right whatever the basic design. It doesn't tell us anything
> about the relative importances of fatigue and ejection.
>
> > My claim is that the fatigue hazard is entirely jim beam's
> > invention.

>
> Yes, I also give jim beam the credit for pointing out the fatigue
> hazard.


Pointing out the *presumed* fatigue hazard and then treating the
presumption as fact is more like it. There's no hard evidence to
support jim's claim that this is a hazard. And, of course he neglects
to mention that existing brake caliper bolts and their mounts are not
loaded only in compression. This varies with the design of the mounts,
of course, as there are several in use. Hayes makes something like 13
different adapters for their brakes!
 
T

Tim McNamara

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> Tim McNamara wrote:
> > In article <[email protected]>,
> > jim beam <[email protected]> wrote:
> >
> >> Tim McNamara wrote: <snip ****>
> >>
> >>> The simple truth, jim, which you have been fending off for years
> >>> is that there is no necessity to have a design that results in an
> >>> ejection force on the front wheel. It can be readily remedied
> >>> and- since it appears that several manufacturers have made
> >>> adjustments in their design to result in a safer product- it has
> >>> been. You've spent all this time and effort trying to disparage
> >>> and defeat and even humiliate- how many posts in this thread
> >>> alone?- and yet your position is still one of senseless denial.
> >> oh the irony. it would be funny if you understood it.

> >
> > I do understand the point you are trying to make.

>
> no you don't. you think you do, but you don't know what you don't
> know. even when presented with the answers, your ability to connect
> them with fundamental principals is repeatedly shown to be non
> existent. add a generous dose of stubbornness, and a research thesis
> presents itself.


LOL. Pot, kettle, black, dude. Jeez, you are such a riot to read.

> > And I think you're- once again- just plain wrong.

>
> you don't understand basic math tim.


LOL. Fortunately my puny math skills are adequate to the task.

It would seem, jim, that you are unable to comprehend the simple fact
that I can understand your position and still disagree with it. You
appear so convinced of your rightness, and so committed to your
conviction, that you can't see the forest for the trees.

> > Since you are reduced to "am not" and "are too" type arguments, and
> > have already called Frank an idiot twice in this thread,

>
> that's because he /is/ an idiot.


And yet he is a mechanical engineer, and you are not. Hmmm. In fact,
it appears that all the mechanical engineers in this thread disagree
with you. Hmmm.
 
A

A Muzi

Guest
>>> Ben C <[email protected]> wrote:
>>>> The point is that wheel ejection is a molehill of similar proportions.


[email protected] wrote:
>>> If you want to prove the front-mount-fatigue issue is of similar
>>> importance to the bike wheel ejection issue, it should be easy for you
>>> to do so. Just post here the tales of motorcycles losing their front
>>> mount calipers due to fatigue.


>>> Ben C <[email protected]> wrote:

>> If no such tales can be found that just proves that the motorcycle
>> designers made sufficiently strong or fatigue-resistant caliper mounts
>> to overcome the problem. I would expect the likes of Honda to get that
>> right whatever the basic design. It doesn't tell us anything about the
>> relative importances of fatigue and ejection.


[email protected] wrote:
> It doesn't take "the likes of Honda" to get that feature right. The
> problem is simple enough that sophomore students in mechanical design
> can get it right easily, and without the need for any sophisticated
> FEA software.
>
> I think you're overly impressed with the idea of tensile fatigue, and
> don't realize how routine it is to design components that successfully
> handle it.
>
> Look at your front brake's caliper arms again. They undergo a tensile
> fatigue cycle each time you apply your brakes, due to bending
> stresses. Have you ever had a caliper arm fatigue? Have you ever
> seen one that did fatigue? Have you ever heard a tale of a person
> injured, or nearly injured, because of such a thing?
>
> That particular molehill is microscopic.


It's too bad we were diverted to that tangent. I suspect that with
modern formed dual-leg aluminum fork bottoms, a _front_ disc mount
probably wouldn't be all that different. (I'm _not_ a fork designer!
Just my WAG)

Back in the world of bicycles, where canti/V mounts don't pop off the
front either, I wonder why fork makers have not offered front disc as an
option? They are already able to sell end-cap forks with special wheel
hardware at a premium. You'd think there's money laying on the table . . .

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

Tim McNamara

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> dabac wrote:
> > jim beam Wrote:
> >> ....the real consideration of course is how great the collapsing
> >> force is in relation to capacity, not whether a collapsing force
> >> exists....

> >
> > But you're completely ignoring the different orders of magnitude of
> > effort needed to address the different issues. Old school risk
> > reduction principles tended to foster a tunnel visioned approach
> > like that. Sure, wheel ejection is rare and avoidable through known
> > means, and there are other failures that are far more common and
> > equally if not more critical. But are there any who are as easily
> > corrected and with as little impact on the whole concept of bike
> > riding/bike owning as changing dropout angle and/or caliper
> > location(even if it only is to top mount and not forward mount)?
> >
> > Of course one could, in the interest of safety, require that all
> > bike components should be redesigned with a bigger safety margin
> > and with redundancy on critical systems(2-circuit for hydraulic
> > brakes, double clamps on wire operated etc), but that would have a
> > major impact on just about every aspect on riding, servicing and
> > bike ownership. Assuming that fork molds gets changed regularly
> > anyhow changing dropout angle and caliper location OTOH makes an
> > admittedly small risk go away w/o any rider consequences.
> >
> >

> to some extent, and i've said as much before.


Oh ********.

> but q.r. failure, the biggest issue in all this, will still lead to
> disaster, angled dropouts or not. all this chicken little b.s. based
> on irrational fears created by bad math, with the biggest adherents
> being non-engineers that can't grasp the most basic fundamentals, it
> beyond bizarre.


LOL. Perhaps somehow you keep overlooking the fact that two of the
biggest "adherents" *are* mechanical engineers, whereas the biggest
opponent *is not.*

> focus on the freakin' q.r., that's the safety issue, not the
> dropouts.


Duck, weave, circle and dodge.
 
T

Tim McNamara

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> Tim McNamara wrote:
> > In article <[email protected]>,
> > jim beam <[email protected]> wrote:
> >
> >> Tim McNamara wrote:
> >>> In article <[email protected]>,
> >>> jim beam <[email protected]> wrote:
> >>>
> >>>> [email protected] wrote:
> >>>>

> >
> > <snip>
> >
> >>>>> Twenty years later, the major trials manufacturers--GasGas,
> >>>>> Sherco, and Beta--are still building leading-caliper trials
> >>>>> bikes and trailing-caliper off-road machines.
> >>>>>
> >>>>> So the leading caliper disk brake is "traditional" on trials
> >>>>> machines, but it's a tradition peculiar to trials and a
> >>>>> tradition that required changing the existing tradition of
> >>>>> trailing calipers on all other machines.
> >>>>>
> >>>>> Anyone who's ridden trials will easily appreciate the advantage
> >>>>> of having the caliper up higher in the leading position, where
> >>>>> rocks don't smash it so easily when you step off a doomed
> >>>>> machine.
> >>>>>
> >>>> accepted. the point is, there's a specific reason to go to the
> >>>> "dark side", and you've identified it.
> >>> But clearly no specific reason *not* to, since that arrangement
> >>> obviously works without the dire failures you predict.
> >> did you notice my post about safety earlier today? how much do
> >> you want to pay to make front calipers "safe"?

> >
> > jim, your style of posting makes it impossible to track every thing
> > you say. You've never learned how to snip extraneous material from
> > your posts, you bury three words in the middle of 200 lines and
> > stuff you write sometimes just gets lost.
> >
> > Which calipers are you taking about? Disk brakes calipers? Rim
> > calipers? Digital calipers? Dial calipers? (OK, I'm being
> > silly.)

>
> trivialization of inconvenient truth.


LOL. So now you're the Al Gore of r.b.t! Woot! And I notice that you
ducked the question.

> > The proposed changes are really quite trivial and there is no
> > reason for there to be a significant differential in cost. As Carl
> > points out, there are plenty of examples of successful designs that
> > put the disk caliper in front of the fork leg. It would appear
> > that the issue of tensile fatigue is not as dire as you predict,
> > given that the total load and instantaneous load on the caliper
> > mounts would be much higher on a motorcycle.

>
> again, did you read my post? it's all about how much you want to
> pay. and paying to fix a problem that isn't? that's illogical.


Yes, and I was pointing out that you weren't making the slightest bit of
sense (yet again). Your reading comprehension and writing skills are
not improving.
 
On Feb 14, 1:39 pm, "Ed Pirrero" <[email protected]> wrote:
> On Feb 13, 9:20 pm, [email protected] wrote:
>
> > On Feb 13, 9:17 pm, "G.T." <[email protected]> wrote:

>
> > > EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
> > > Pinder, and I doubt they'll trust anyone else who claims they checked their
> > > QRs before the QRs magically loosen.

>
> > I think this is true...

>
> Then you think wrong. Just like GT. You bring this up every time
> this discussion occurs, as a handy device to dismiss any questions
> about what could be baseless assumptions on your part.


If you refuse to believe everyone's statement that they paid attention
and properly clamped their QR, then what I think is _not_ wrong.

>
> > EP and jb go on about initial conditions not being verified (or some
> > such thing) without ever specifying what they'd accept as a standard
> > for verification.

>
> I'd like to see SOME sort of second opinion.


So you need two people to check the same QR? That is, it doesn't
matter if a witness confirms observing the rider tightened it
properly?

I guess that's what you mean, because IIRC, some accounts have
witnesses confirming that the rider did diligently check it. But
apparently, that's not good enough either.

> For anyone who's ever
> ridden off, only to look down and see the QR loose (disk brake or
> not), knows exactly what I'm talking about. Certainly that wasn't
> done on *purpose*, so that person obviously thought they had done it
> up, and done it up correctly.


The example you give (which, BTW, has never happened to me) is not the
same. It's not a question of someone completely forgetting to tighten
their QR; the situation is reported as someone deliberately setting
their QR, yet having it come loose.

> I'll repeat it again, since you and G.T. can't seem to get it the
> first eight or twevle times I've said it: Nobody, no you, not me,
> *nobody* - knows the initial conditions with certainty. You make the
> assumption that the initial conditions are as reported, and I don't.


That last part is correct. You make the assumption that when
professional or long-experience mountain bikers double check their
QRs, they may still accidentally have them loose without knowing it.
To me, that's stretching incredulity into fantasy.

If, say, Missy Giove can't be trusted to tell if her QR is tight, then
I assume nobody can. So, like jim beam, you've set a standard for
verification that's practically impossible to achieve.

Again, that's very handy for someone who wants to attribute all
equipment failures to operator error!

- Frank Krygowski
 
E

Ed Pirrero

Guest
On Feb 14, 3:41 pm, [email protected] wrote:
>
> Again, that's very handy for someone who wants to attribute all
> equipment failures to operator error!


I guess if you keep on lying about it, it'll become true, right?

E.P.
 
On 14 Feb 2007 14:11:55 -0800, [email protected] wrote:

>On Feb 14, 1:26 pm, Ben C <[email protected]> wrote:
>> On 2007-02-14, [email protected] <[email protected]> wrote:
>>
>> > On Feb 14, 3:48 am, Ben C <[email protected]> wrote:

>> [...]
>> >> The point is that wheel ejection is a molehill of similar proportions.

>>
>> > If you want to prove the front-mount-fatigue issue is of similar
>> > importance to the bike wheel ejection issue, it should be easy for you
>> > to do so. Just post here the tales of motorcycles losing their front
>> > mount calipers due to fatigue.

>>
>> If no such tales can be found that just proves that the motorcycle
>> designers made sufficiently strong or fatigue-resistant caliper mounts
>> to overcome the problem. I would expect the likes of Honda to get that
>> right whatever the basic design. It doesn't tell us anything about the
>> relative importances of fatigue and ejection.

>
>It doesn't take "the likes of Honda" to get that feature right. The
>problem is simple enough that sophomore students in mechanical design
>can get it right easily, and without the need for any sophisticated
>FEA software.
>
>I think you're overly impressed with the idea of tensile fatigue, and
>don't realize how routine it is to design components that successfully
>handle it.
>
>Look at your front brake's caliper arms again. They undergo a tensile
>fatigue cycle each time you apply your brakes, due to bending
>stresses. Have you ever had a caliper arm fatigue? Have you ever
>seen one that did fatigue? Have you ever heard a tale of a person
>injured, or nearly injured, because of such a thing?
>
>That particular molehill is microscopic.
>
>- Frank Krygowski


Dear Frank & Ben,

To clarify things, disk brakes first appeared on large, heavy street
motorcycles--and were originally mounted with high leading calipers by
Honda.

In ten years or less, the industry (including Honda) had switched to
overwhelmingly to low trailing calipers.

The only modern leading calipers that I know of are found on trials
machines, where the high leading position helps avoid damaging
calipers when the bikes are dropped to one side or the other in rocks,
a routine hazard.

Trials machines are not designed or certified for road use and
nowadays weigh under 170 pounds. Their braking can be quite savage at
low speeds in stunt-riding maneuvers, with the contact patches at
absurd angles.

I don't know why all other machines switched to low trailing calipers
after the first high leading calipers, but I doubt that it had
anything to do with failures. More likely, the lower trailing caliper
improves handling at normal speeds--the motorcycle calipers and disks
are much larger and heavier than what's found on bicycles.

In any case, the fork tubes and mounting points for motorcycle brakes
are immensely stronger than what's found on bicycles. This is why
truly extreme downhill bicycles are really just motorcycle frames and
suspension without motors.

Any RBT poster interested in such things should stop by a motorcycle
shop or just peek at a parked machine and see how much thicker,
heavier, and stronger motorcycle parts are.

Cheers,

Carl Fogel
 
On Thu, 15 Feb 2007 03:31:28 +1100, dabac
<[email protected]> wrote:

>
>[email protected] Wrote:
>> ...
>> Elsewhere in this thread, I've pointed out that the fellow whose QR
>> came "completely open" explained that he had just become really
>> paranoid about the matter. He mentioned no previous QR problems, but
>> strangely his QR obligingly came undone shortly after he checked it.
>>
>> So I'm wondering why QR's that apparently never popped open before
>> people read about the possible danger promptly pop open as soon as
>> they hear about the problem.
>>
>> It seems odd to me. Does it seem odd to you?
>>
>>

>
>But there's a significant element of "chicken or the egg" in this -
>what came first, the phenomenon or the phrase? An event that previously
>might have been shrugged off as "one of those things", or "sh*t happens"
>is far more likely to get noticed when someone has defined it and given
>it a nice label.
>
>Recent medical history offers a couple of examples on how media
>attention seemingly overnight can increase the number of afflicted
>considerably, e.g. sensitivity to electro-magnetic radiation, mercury
>poisoning from dental amalgam and more recently fibromyalgia and
>chronic fatigue syndrome.
>
>(I'm not trying to be rude to those truly suffering from any of the
>above, but the media influence is intriguing.)


Dear Dab,

You may find the great Australian repetitive stress injury epidemic
interesting:

http://www.metroactive.com/papers/metro/07.03.96/ergonomics2-9627.html

http://www2.aaos.org/aaos/archives/acadnews/98news/carp-22.htm

http://www.uow.edu.au/arts/sts/bmartin/pubs/88chs.html

Cheers,

Carl Fogel
 
J

jim beam

Guest
Tim McNamara wrote:
> In article <[email protected]>,
> Ben C <[email protected]> wrote:
>
>> On 2007-02-14, [email protected] <[email protected]> wrote:
>>> On Feb 14, 3:48 am, Ben C <[email protected]> wrote:

>> [...]
>>>> The point is that wheel ejection is a molehill of similar
>>>> proportions.
>>> If you want to prove the front-mount-fatigue issue is of similar
>>> importance to the bike wheel ejection issue, it should be easy for
>>> you to do so. Just post here the tales of motorcycles losing their
>>> front mount calipers due to fatigue.

>> If no such tales can be found that just proves that the motorcycle
>> designers made sufficiently strong or fatigue-resistant caliper
>> mounts to overcome the problem. I would expect the likes of Honda to
>> get that right whatever the basic design. It doesn't tell us anything
>> about the relative importances of fatigue and ejection.
>>
>>> My claim is that the fatigue hazard is entirely jim beam's
>>> invention.

>> Yes, I also give jim beam the credit for pointing out the fatigue
>> hazard.

>
> Pointing out the *presumed* fatigue hazard and then treating the
> presumption as fact is more like it. There's no hard evidence to
> support jim's claim that this is a hazard.


look it up. tables for fatigue strength in castings. it's been posted
here before.

> And, of course he neglects
> to mention that existing brake caliper bolts and their mounts are not
> loaded only in compression.


caliper bolts are mounted in shear. bolts are not cast.

> This varies with the design of the mounts,
> of course, as there are several in use.


no, /all/ caliper bolts are in shear.

> Hayes makes something like 13
> different adapters for their brakes!


and /all/ the caliper bolts are in shear.
 
J

jim beam

Guest
Tim McNamara wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
>> Tim McNamara wrote:
>>> In article <[email protected]>,
>>> jim beam <[email protected]> wrote:
>>>
>>>> Tim McNamara wrote: <snip ****>
>>>>
>>>>> The simple truth, jim, which you have been fending off for years
>>>>> is that there is no necessity to have a design that results in an
>>>>> ejection force on the front wheel. It can be readily remedied
>>>>> and- since it appears that several manufacturers have made
>>>>> adjustments in their design to result in a safer product- it has
>>>>> been. You've spent all this time and effort trying to disparage
>>>>> and defeat and even humiliate- how many posts in this thread
>>>>> alone?- and yet your position is still one of senseless denial.
>>>> oh the irony. it would be funny if you understood it.
>>> I do understand the point you are trying to make.

>> no you don't. you think you do, but you don't know what you don't
>> know. even when presented with the answers, your ability to connect
>> them with fundamental principals is repeatedly shown to be non
>> existent. add a generous dose of stubbornness, and a research thesis
>> presents itself.

>
> LOL. Pot, kettle, black, dude. Jeez, you are such a riot to read.


that's just pissing.

>
>>> And I think you're- once again- just plain wrong.

>> you don't understand basic math tim.

>
> LOL. Fortunately my puny math skills are adequate to the task.


so why can't you grasp the fact that if x>y, y!>x?

>
> It would seem, jim, that you are unable to comprehend the simple fact
> that I can understand your position and still disagree with it. You
> appear so convinced of your rightness, and so committed to your
> conviction, that you can't see the forest for the trees.


no, you just won't accept that there's massive gaps in your
understanding - a gap of a size that you don't know what you don't know.

>
>>> Since you are reduced to "am not" and "are too" type arguments, and
>>> have already called Frank an idiot twice in this thread,

>> that's because he /is/ an idiot.

>
> And yet he is a mechanical engineer, and you are not. Hmmm. In fact,
> it appears that all the mechanical engineers in this thread disagree
> with you. Hmmm.


and there's "mechanical engineers" that think castings are just as good
in tension as they are in compression. it's those kind of "mechanical
engineers" that are responsible for failures.
 
J

jim beam

Guest
[email protected] wrote:
> On Feb 14, 3:48 am, Ben C <[email protected]> wrote:
>> On 2007-02-14, [email protected] <[email protected]> wrote:
>>
>>> But third (and perhaps easiest to understand) is that the specific
>>> thing jim beam warns about - front mounting of disk brakes - has been
>>> employed on multi-hundred-pound motorcycles for many decades. The
>>> direct tensile stresses that come from such mounting are small, and
>>> very easily accommodated. If they were not, NHTSA and CPSC would have
>>> told you about it in the recall documents for those motorcycles.

>> Noone's disputed that a front caliper is possible, but motorbikes are
>> not bicycles.

>
> True. They're much more massive, travel at much higher speeds, and
> impose much higher forces on their caliper attachements.
>
>> All the relative pros and cons are different, which makes
>> it a different optimization problem and we should not be surprised if it
>> has a different solution. Lots of motorbikes do have rear calipers
>> anyway.

>
> Do you know of any motorcycle with a rear caliper and a quick release
> front axle? I don't believe they exist. Every motorcycle I've owned
> or seen had a through-axle. Thus, the hazard imposed by a rear
> caliper was removed by other means.


conversely, why aren't /all/ motorcycles front caliper? idiot.

>
>>> So yes, there's a grain of metallurgical truth in what j.b. says. But
>>> the design proclamations he derives from it are nonsense. He's making
>>> a mountain out of a molehill for reasons of his own.

>> The point is that wheel ejection is a molehill of similar proportions.

>
> If you want to prove the front-mount-fatigue issue is of similar
> importance to the bike wheel ejection issue, it should be easy for you
> to do so. Just post here the tales of motorcycles losing their front
> mount calipers due to fatigue. Carl has posted several examples of
> candidate motorcycles to check. If you find enough such tales, I'll
> believe the hazards are similar.


post front wheel ejections where it's proven not to be user error! idiot.

>
> My claim is that the fatigue hazard is entirely jim beam's invention.


i invented inferior fatigue properties for castings??? you don't even
know what a casting is! idiot.

> You have an opportunity to prove me wrong.


no, you do that on your own. idiot.
 
J

jim beam

Guest
[email protected] wrote:
> On Feb 14, 1:00 am, jim beam <[email protected]> wrote:
>> [email protected] wrote:
>>> So yes, there's a grain of metallurgical truth in what j.b. says. But
>>> the design proclamations he derives from it are nonsense. He's making
>>> a mountain out of a molehill for reasons of his own.

>> coming from a guy that doesn't understand bending stresses, that's
>> pretty peachy.

>
> :)
>
> When the State Board of Examiners graded my test for the Professional
> Engineeer's license, they heartily disagreed with you.
>
> - Frank Krygowski
>

so why can't you get your bending stress sense correct then? did
someone else do that test for you?
 
J

jim beam

Guest
[email protected] wrote:
> On Feb 14, 3:11 am, Ben C <[email protected]> wrote:
>
>>> [J.B.] I think this is not the place to learn about material science.

>> It's better than nothing.

>
> Actually, it goes beyond that. This is also not the place to learn
> about mechanical design to resist fatigue failure, and that's really
> what we're discussing at the moment. j.b. appears to know something
> about metallurgy, but he knows too little about mechanical design.
> It's principles are by no means obvious. You won't learn them here,
> and certainly not from jim beam.


he'll learn more than from you if you can't get your bending stress
sense correct.
 
J

jim beam

Guest
Jay Beattie wrote:
> On Feb 10, 12:18 pm, Gary Young <[email protected]> wrote:
>> On Sat, 10 Feb 2007 11:13:08 -0800, Ed Pirrero wrote:
>>> On Feb 10, 11:03 am, Gary Young <[email protected]> wrote:
>>>> On Sat, 10 Feb 2007 10:43:57 -0800, Ed Pirrero wrote:
>>>>> On Feb 10, 8:47 am, [email protected] wrote:
>>>>>> On Feb 9, 11:18 pm, Mark Hickey <[email protected]> wrote:
>>>>>>> I'm a "skewer skeptic" (sic) based on the following assumptions...
>>>>>>> 1) A number of people will fail to properly tighten their skewer
>>>>>>> before a given ride. This might be from inattention, or could be
>>>>>>> because the skewer caught the edge of the lawyer lip or other
>>>>>>> debris (preventing it from fully closing).
>>>>>>> 2) The number of wheel ejections we've heard about (directly and
>>>>>>> indirectly) are quite small.
>>>>>>> 3) I think it's very reasonable to assume that the number of case
>>>>>>> number 1 scenarios could eaily exceed the number of case number 2
>>>>>>> scenarios. Ipso facto, it's not at all unreasonable to assume
>>>>>>> that I've got very little to worry about when I'm riding my MTB.
>>>>>> While all three of your points are correct, they don't make the
>>>>>> problem go away.
>>>>>> Point 1 is correct, but from the reports we've read, the problem has
>>>>>> been demonstrated many times by people who almost certainly did
>>>>>> fasten the QR properly.
>>>>> Without any verification, "almost certainly" is pretty gratuitous.
>>>>> Taking data from uncontrolled experiments and using it as evidence is
>>>>> normally called "junk science."
>>>>>> (If j.b. or others say _all_ those people failed to tighten
>>>>>> properly, despite pre-knowledge of the problem and lots of prior
>>>>>> experience, I expect they'd deny any lab test based on the same
>>>>>> criterion!)
>>>>> That's a strawman, and we both know it. Neither you nor I know the
>>>>> conditions under which the QRs in those stories were tightened, and
>>>>> have absolutely no clue what the initial conditions were.
>>>>> If it were an experiment from a grad student, for publication, would
>>>>> you let that slide?
>>>>> Well, *you* might, but the publication wouldn't.
>>>>>> Point 2 is correct, IMO, simply because the problem is limited
>>>>>> almost exclusively to a single riding situation: long, bumpy
>>>>>> downhills with hard braking.
>>>>> We have such conditions out here in the Western U.S. In fact, I
>>>>> would suggest that those sorts of conditions prevail in MTB country -
>>>>> CO Front Range, Moab area in Utah, Arizona, CA, etc. There are LOTS
>>>>> of mountain bikers in those areas, and folks who are pretty serious
>>>>> about their riding.
>>>>> And yet, the stories of loosening don't come from there, but from the
>>>>> comparatively flat region of the world known as the United Kingdom.
>>>>> This anomaly seems to be ignored by the pro-redesign crowd - for
>>>>> reasons I cannot fathom.
>>>>> I also ride in the West U.S. - ID, to be clear. There are a LOT of
>>>>> long, steep, bumpy downhills. In fact, one of my regular rides
>>>>> requires me to ride about 5 miles of wide doubletrack and fire road
>>>>> so that I can ride down one mile of very bumpy, steep and twisty
>>>>> singletrack. Never had any loosening.
>>>>>> Point 3 is probably correct, since the odds are you "Point 2" type
>>>>>> riding fairly infrequently - and because you've read these
>>>>>> discussions, you'll be damned sure to watch for the problem!
>>>>> This is correct. I regularly inspect my front QRs. More now, but I
>>>>> did do it before I had disk brakes.
>>>>>> Still, there are folks who will not have heard of this, who will buy
>>>>>> "good" equpment, use it as directed, and put themselves at great
>>>>>> risk.
>>>>> This assumes facts not in evidence.
>>>>>> That's a description of a faulty design.
>>>>> Actually, MTBing starts out being kinda risky. I have known a few
>>>>> folks who have broken rear triangles on their FS MTBs, and crashed as
>>>>> a result. One of those guys had a broken femur, and had to be
>>>>> carried 4 miles out. He was using the equipment as designed. And
>>>>> yet this brand of MTB and this model is sold a lot. I suppose a
>>>>> recall or redesign is in order?
>>>> If the design could be improved at a reasonable cost, then yes, a
>>>> redesign would be in order.
>>> Because ONE guy got hurt? That's pretty knee-jerk...
>>>> If some failure is inevitable given even the best in design, then no, a
>>>> redesign would not be in order.
>>> I think this would be the case with EVERY mechanical item. And
>>> sometimes "best" is not cost-effective.

>> Agreed. That's why I said the change should be made if it can be done at
>> reasonable cost. It may be hard to quantify what's reasonable, but the law
>> generally asks juries to look at what an average consumer would expect for
>> his money. If informed consumers are generally willing to accept a certain
>> tradeoff between cost and safety, then that's generally deemed reasonable.
>> (while I think that's an accurate overview, the case at hand might be
>> treated differently because the brake placement might be considered a
>> design defect triggering strict liability -- I'm sure JayBeattie, if he's
>> following this thread, could give a more accurate picture.) You can't just
>> look at the costs to the manufacturers, because they have an interest in
>> imposing their costs onto the consumer (that is, refusing to pay the price
>> for externalities).
>>
>> One of the ways that manufacturers get away with imposing externalities on
>> consumers without compensation is by failing to disclose defects. If
>> consumers don't know about a defect, they are likely to chalk up failures
>> to other factors -- user error, unavoidable fatigue, etc.
>>
>> To me, that means that at the very least manufacturers should be required
>> to disclose this problem to their consumers. Suppose, for instance, that
>> fork makers were required to include with their forks and in
>> advertisements the following message:
>>
>> Dear consumer:
>> Applying your front disk brake creates a force that tends to eject the
>> wheel from the dropouts. Our research leads us to believe that this is not
>> a problem in practice if you use your quick release in the proper fashion.
>> Please follow carefully our instructions regarding quick releases.
>>
>> What would be your objections to that? I know why manufacturers would fear
>> that, though they might not say it out loud -- a lot of consumers would be
>> leery of buying a fork from someone boneheaded enough to place the brake
>> in a way that tends to eject the wheel.
>>
>>>> After all, if it's possible to get hurt, a> redesign is

>> necessary,
>>>> right?
>>>> No one is saying anything that silly.
>>> Actually, they are. AFAIK, there are zero proven disk-ejection
>>> injuries. There have been a lot of assumptions made, but very little
>>> proof.

>> So we have to wait for someone to get killed or seriously injured before
>> we take action? Why? Why not no killings or serious injuries from this
>> cause?
>>
>> Given what you've said above, one indisputable case still wouldn't be
>> enough for you: "Because ONE guy got hurt? That's pretty knee-jerk..."
>> How many bodies have to pile up before you'd think action is necessary?
>>
>>
>>
>>> And yet, on the basis of assumption, and no real data, people are crying
>>> for a redesign. Because of the possibility that someone might get hurt,
>>> when all the assumptions line up in a specific way.
>>> E.P.- Hide quoted text -

>> - Show quoted text -- Hide quoted text -
>>
>> - Show quoted text -

>
>
> I've been busy doing the dirty-work of evil manufacturers, so I
> haven't followed along much. Anyway, under a strict "consumer
> expectation" test, a bicycle or component manufacturer is subject to
> liability if a design or manufacturing defect makes a product more
> dangerous than expected by a reasonable consumer -- this is the so-
> called "consumer expectation" test. So, if a reasonable consumer
> does not expect his/her front wheel to be ejected by braking forces,
> and the wheel does eject, then the wheel/brake/bike (whatever part is
> the culprit) is dangerously defective, and the manufacturer is subject
> to liability (with the usual comparative fault/misuse/modification
> defenses).
>
> California came up with a "risk-utility test" to supplement the
> consumer expectation test maybe 40 years ago to deal with products
> that were obviously dangerous (and were expected to cause injury) or
> which were so complicated that no consumer had an expectation
> concerning safety. Cigarettes, for example, are not unreasonably
> dangerous under the consumer expectation test because everyone knows
> they will kill you. They flunk the risk-utility test, though because
> they have no utility. You don't even need to use the risk-utility
> test with front brakes, though, since they are not obviously dangerous
> and we do not expect them to eject the front wheel. All you need to
> do is tie the ejection to a "defect" (the placement of the caliper)
> and not to some schmuck failing to tighten a quick release.
>
> I represent some big bicycle manufacturers and have not seen a disc
> brake wheel ejection case in Oregon. In fact, I wish they would
> start ejecting so I could get some more bicycle work. Anyone in
> Oregon who is considering getting injured, please do so in the Bend
> are during winter so I can work in some skiing on Batchelor. Nobody
> should get injured in Lakeview, ever, since it is a gawdawful long
> drive through endless scrub. Thank you. -- Jay Beattie.
>


good post.

question: in a situation where there is a known risk, but another known
benefit with a certain design, then what happens? example: most modern
cars have negative scrub radius for their steering. it's "safe" because
it tends to counteract the steering effect of a front tire flat at speed
thereby allowing an unskilled driver more chance of retaining control
and bringing the vehicle to a halt in a controlled manner. but the
danger is that it makes steering feel light [and therefore "safe"] when
braking /through/ corners, thereby encouraging that unsafe habit.
physics will tell you that braking through corners is a bad thing, and
positive scrub makes braking through feel heavy and uncertain, thereby
discouraging that kind of bad behavior. how might a legal test be
applied to that?
 
J

jim beam

Guest
Tim McNamara wrote:
> In article <[email protected]>,
> Ben C <[email protected]> wrote:
>
>> On 2007-02-14, [email protected] <[email protected]> wrote:
>>> On Feb 14, 3:48 am, Ben C <[email protected]> wrote:

>> [...]
>>>> The point is that wheel ejection is a molehill of similar
>>>> proportions.
>>> If you want to prove the front-mount-fatigue issue is of similar
>>> importance to the bike wheel ejection issue, it should be easy for
>>> you to do so. Just post here the tales of motorcycles losing their
>>> front mount calipers due to fatigue.

>> If no such tales can be found that just proves that the motorcycle
>> designers made sufficiently strong or fatigue-resistant caliper
>> mounts to overcome the problem. I would expect the likes of Honda to
>> get that right whatever the basic design. It doesn't tell us anything
>> about the relative importances of fatigue and ejection.
>>
>>> My claim is that the fatigue hazard is entirely jim beam's
>>> invention.

>> Yes, I also give jim beam the credit for pointing out the fatigue
>> hazard.

>
> Pointing out the *presumed* fatigue hazard and then treating the
> presumption as fact is more like it. There's no hard evidence to
> support jim's claim that this is a hazard.


whoops, missed that peachy bit! now let me get this straight - a
presumed hazard cannot be taken as fact? is that correct? a presumed
hazard like disk ejection? i just want to be sure because materials
literature is full of data on casting fatigue behavior - that's known to
most people as "hard evidence".

> And, of course he neglects
> to mention that existing brake caliper bolts and their mounts are not
> loaded only in compression. This varies with the design of the mounts,
> of course, as there are several in use. Hayes makes something like 13
> different adapters for their brakes!
 
J

jim beam

Guest
Tim McNamara wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
>> dabac wrote:
>>> jim beam Wrote:
>>>> ....the real consideration of course is how great the collapsing
>>>> force is in relation to capacity, not whether a collapsing force
>>>> exists....
>>> But you're completely ignoring the different orders of magnitude of
>>> effort needed to address the different issues. Old school risk
>>> reduction principles tended to foster a tunnel visioned approach
>>> like that. Sure, wheel ejection is rare and avoidable through known
>>> means, and there are other failures that are far more common and
>>> equally if not more critical. But are there any who are as easily
>>> corrected and with as little impact on the whole concept of bike
>>> riding/bike owning as changing dropout angle and/or caliper
>>> location(even if it only is to top mount and not forward mount)?
>>>
>>> Of course one could, in the interest of safety, require that all
>>> bike components should be redesigned with a bigger safety margin
>>> and with redundancy on critical systems(2-circuit for hydraulic
>>> brakes, double clamps on wire operated etc), but that would have a
>>> major impact on just about every aspect on riding, servicing and
>>> bike ownership. Assuming that fork molds gets changed regularly
>>> anyhow changing dropout angle and caliper location OTOH makes an
>>> admittedly small risk go away w/o any rider consequences.
>>>
>>>

>> to some extent, and i've said as much before.

>
> Oh ********.


you see tim, you huff and you puff, but you don't read the thread.
other evidence suggests you don't understand much of it even if you do.

>
>> but q.r. failure, the biggest issue in all this, will still lead to
>> disaster, angled dropouts or not. all this chicken little b.s. based
>> on irrational fears created by bad math, with the biggest adherents
>> being non-engineers that can't grasp the most basic fundamentals, it
>> beyond bizarre.

>
> LOL. Perhaps somehow you keep overlooking the fact that two of the
> biggest "adherents" *are* mechanical engineers, whereas the biggest
> opponent *is not.*


one doesn't know the difference between the fatigue characteristics of a
material that strain ages and one that doesn't. the other doesn't know
the sense of stress in bending. are they both useful to you in this
appeal to an authority /you/ don't have?

>
>> focus on the freakin' q.r., that's the safety issue, not the
>> dropouts.

>
> Duck, weave, circle and dodge.


no tim, /you/ focus on the pertinent facts.