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"Actually you are the first person to bring up this issue" - Page 5

post #61 of 402

Re: "Actually you are the first person to bring up this issue"

jobst.brandt@stanfordalumni.org wrote:
>
> Do you not believe that current disc brakes cause a
> disengaging force? If not, why not? Did you try the test
> of pushing the bicycle forward with an open QR and
> applying the disc brake? If so, did you not notice that
> the fork lifts off the axle. You dismiss "line drawings
> and vector calculations" although you are surrounded by
> machines that are designed by these methods and find them
> reliable. The test I offer does not rely on such
> derivative methods and gets directly to the issue. How
> about trying that and apply your own analysis to it.

As I'm sure you agree, it's not a question of belief, it's a
question of physics. I have no doubt the forces act as
described. I don't dismiss them, but I wonder what's missing
from the equation. Disk brakes aren't so new, but where's
the empirical data to suggest that this is a problem that
needs solving? Even anecdotally there's not much to go on.
Here in AM-B (yeah, this is cross-posted) there's some
serious riders putting some hard miles on disk brakes.
There's always lots of discussion in these QR/Disk threads,
but very little of "Yeah, let me tell you about my
experience...." I'd expect to find it here, if anywhere. A
quick look around the internet suggests all roads return to
our friend Mr Annan. Scientific? Not at all, but suggestive
enough to form a hypothesis that there are variables that
aren't being considered. Could it be that the cases that
have occurred are due to failure of substandard QR's? Why
hasn't this come out of the statistical noise level, despite
the attention of the cycling public?
>
>> To illustrate, my lovely wife subscribes to the CPSC
>> mailing list. We receive an email nearly ever day listing
>> between 1 and 5 different product recalls. These recalls
>> typically describe what is often potential flaws and
>> possible dangers -- many of which are damn near laughable
>> but still result in a recall:
>
>> Here's a few examples: http://tinyurl.com/223qd
>> http://tinyurl.com/2n2sn
>
> These both seem reasonable hazard warnings. The tire pump
> has a check valve failure, something that has ejected pump
> handles to the ceiling and the helmet doesn't meet
> specifications. What is "laughable" about that.

My point exactly! Okay, laughable may be the wrong term, but
the point should be pretty clear. CPSC will issue warnings
about products which result in chipped teeth and broken
fingers, but assiduously avoids tackling the potentially life-
threatening disk-brake phenomenon? Why's that? Consumers
will report minor injuries from a bad pump design, but run
away from the thought of reporting serious trauma caused by
their front wheel flying off? It just doesn't compute. Or do
people just dismiss it as bad luck without wondering why it
happened? With all the angst in these NGs, I can't imagine
it's an issue that hasn't been examined by the
quintessential gov't nanny. Or are you going to espouse the
manufacturer - gov't conspiracy theory now, too?
>
>> Surf the site and ask yourself if the CPSC is going to
>> overlook the disk brake risk when bicycle product recalls
>> are issued for injuries no more severe than a broken
>> finger.
>
> http://tinyurl.com/3yxvb
>
> I think you missed the explanations for this. I concur
> that without someone reporting an injury from it, CPSC
> won't pick it up. The cause for a wheel disengagement is
> not obvious and from what we read here, even difficult to
> explain how a disc brake can cause a QR to loosen or for
> that matter cause an axle to disengage from the fork.
>
You argue above that the disengagement forces are easily
demonstrated, but now suggest they're not obvious in the
empircal world? Which is it? Again, this smacks of a
theoretical problem that, for whatever reason, doesn't
manifest itself in reality. Where are all the injuries? Why
*haven't* they been reported? I'm not disputing the effect,
merely suggesting it's not quite the hazard it's made out to
be. Barring outright conspiricy, if the CPSC will issue this
recall: http://tinyurl.com/2gktb where no injuries were
reported, then why would they reject the bigger "problem" ?

>
>> Hell, I don't even ride with disks and I think the whole
>> debate is a crock.
>
> So why do you get so vehement about this issue that you
> call those who understand it names and imply they are
> fabricating the effect?
>
I'm not so much vehement as someone who enjoys a lively
conversation. Any criticism or name calling is reserved for
those who's logical inconsistency or outright silliness
brings what they say into question. In the same vein, I've
noticed a bit of sting in your posts on occasion too, Jobst.
I'm no saint, but this is usenet after all. I'm not
suggesting the effect is fabricated, either. I'm suggesting
the danger is more theoretical than actual. It may just be
that riders manage to tighten their QRs and check them
enough to reduce the incidence of *actual* disengagement
down into the noise level. I don't doubt that disengagement
*could* happen, I just have doubts it does happen enough to
warrent accusations of cover-up. I don't feel like rereading
the whole thread to find the comments, but I recall the evil
profit motive of the bike makers has been cited as a reason
for inaction on the disk design "crisis."

From what I've read, it seems perfectly reasonable that
redesigning the brake bosses will eliminate the issue. Maybe
someday a manufacturer will retool and do so. However I
still wonder if there are other considerations that preclude
such redesign -- other than the conspiricy. If it's so
simple, then why did the industry adopt the current standard
(flawed as it may be)? Likewise, if the theoretical problem
proves to be a statistically significant cycling hazard then
the various countries consumer agencies will hopefully step
in. Why hasn't it happened yet?

Every time I get on a bike there's risk. I don't condone
unneeded risk and support avoiding known and potential
hazards, but let's worry more about the actual rather than
the potential risks. How about all those crappy handlebars
and seatposts that break even under normal riding
conditions. There's some bad designs out there. How many
injuries result from the crappy design of clipless pedals
that are difficult to disengate when you need to? Where's
the uproar there?

Bottom line for me: I'm always skeptical about personal
crusades based on theoretical constructs. Remember the Alar-
apple scare years ago? I've no doubt there was some serious
scientic scholarship on the effect of alar on the human
body. The problem, however, was the hysteria that followed
was not warrented by any empirical evidence of it's impact
on human health. I don't reject the notion outright, but I'm
skeptical about whether it's a real problem in search of a
solution, or just one more reason among many to check the QR
before riding.

Tom
post #62 of 402

Re: "Actually you are the first person to bring up this issue"

In article <3W_6c.1044$V66.897@newsread3.news.atl.earthlink.net>,
Jose Rizal <_@_._> wrote:

> Ryan Cousineau:
>
> > Is it really so bad for the bolts to be in tension? As I
> > understand this stuff, the way a bolt works is that when
> > you tighten it properly, you're effectively loading it
> > with a whole bunch of tension.
> >
> > http://www.unified-eng.com/scitech/bolt/clamping.html
>
> This is right, but torquing a bolt for holding parts
> together is different from getting that bolt's threads to
> take a load above its torque specification because it's
> not always just the bolt you worry about, but what it's
> threaded into. Depending on length of engaged thread, it's
> possible to have the threaded contact area to be smaller
> than the bolt's radial cross-sectional area which means
> that even though the bolt itself can survive the tensile
> load, the threads on either the bolt or the material it's
> screwed into might not. See below.

> You need to look at the mounting post threads strength,
> not the bolts themselves. The posts are made of aluminium
> and don't have the characteristics you outlined above. The
> post will strip first before the bolt . Using _threads_ on
> bolts to take up loads is always bad design; using the
> bolt body to take up tensile loads is _always_ better.

Here and below you mention this distinction; I assume you
are referring to cases where the bolt is effectively under
zero preload, right? The simplest example would be threading
a bolt loosely into a threaded mount, and then hanging a
weight from the bolt head, right? And the counterexample (of
using the body to take up tensile loads) would be bolting
the bolt tightly into the mount, with the load somehow
acting on a part--a washer, for this example--bolted in
between the bolt and the mount, thus under a lot of
compressive load. Right?

> > > > Of course all these don't matter to IS mounts, where
> > > > the mounting bolts lie perpendicular to the rotor
> > > > plane.

> > Well, it doesn't matter, but now you're loading the
> > bolts in shear, something against which they are not
> > well preloaded and not designed to resist. Look around
> > you in the world: how many examples do you see of shear-
> > loaded fasteners?

> Go into a construction site and be awash with examples.
> Look at the steel girders, beams and other metal support
> structures that are bolted together. Look at the bolted
> structures on bridges; the parts that put bolts in pure
> tensile loading don't rely on the _threads_ to take up the
> load, but on the strength of the bolts themselves.
>
> Bicycle wheel axles are bolts in shear. Imagine a design
> that relies on your QR skewer directly taking up your
> weight in tensile loading.

Considering that we're discussing how QR skewers can be
made to unscrew by moving sideways, maybe this isn't the
best example?

> Maybe, but you can bet money that the "new" radial designs
> will not be relying on bolts' threads taking up the loads
> in tension.

Right. But are "Manitou" mounts on bike brakes (that is, the
equivalent of these radial mounts) really overloading the
threads? That's a design error, from beginning to end. If
the bolt isn't preloaded, it doesn't really do what a bolt
should. Once preloaded, bolts do a very good job of holding
things together. Well, until they're overloaded.

I'm not an engineer, but I have a few mental models of how
this stuff works. I am eager for illumination.

--
Ryan Cousineau, rcousine@sfu.ca
http://www.sfu.ca/~rcousine/wiredcola/ President, Fabrizio
Mazzoleni Fan Club
post #63 of 402

Re: "Actually you are the first person to bring up this issue"

jobst.brandt@stanfordalumni.org:

> Jose Rizal writes:
>
> >> Just so it is clear what occurs. The fork dropout rises
> >> from the axle and is retained only by the retention
> >> lips. the motion involved will cause a properly closed
> >> QR to loosen on repeated hard braking because there is
> >> ever so little motion with each brake application. If
> >> the QR is extremely tight, it can prevent this over a
> >> longer time but in the long run, if the wheel is not
> >> removed for one reason or another and reinstalled again
> >> made extra tight, it will loosen.
>
> > I'm not sure that this occurrence is inevitable. The QR
> > skewer doesn't sit snugly inside the hollow axle; when
> > the QR is tightened it doesn't necessarily follow that
> > the QR rod is resting against the axle. Therefore, the
> > axle can move along the dropout without the skewer
> > moving, especially if it's only ever so little motion.
> > It follows then that this annular gap between the QR
> > skewer and the axle will require a relatively larger
> > axle movement to affect the skewer. Granted that the
> > skewer won't be always perfectly concentric with the
> > inside of the axle when QRs are done up, but the gap
> > still exists and therefore tiny axle motion doesn't
> > necessarily mean QR motion as well.
>
> >> The point is that the wheel should not have disengaging
> >> forces while braking.
>
> > True enough. However, I think QR loosening while braking
> > needs to be treated as a separate issue.
>
> OK, how about addressing this issue now. Rather than
> saying it doesn't happen from braking in face of
> explanations on how it can and does occur.

Your explanation of QR loosening with disc braking is
lacking because of the situation I outlined above, with
respect to the annular gap between axle and skewer. How do
you reconcile the fact that the QR skewer and the hub axle
do not form one rigid structure that are directly connected
and that move together, but rather two different items which
need to overcome an annular gap in order to move together.
Add to this the fact that no one reports observing
significant scoring of inner dropout surfaces, necessary
because the axle needs to move cyclically by just a bit over
1mm in order to make contact with and push the skewer rod up
and down. Further add to this the fact that QR knobs are
able to swivel by a small amount about the skewer tips,
adding to the length of movement of the skewer that is
necessary to displace the QR knobs.

You have nothing but anecdotes for QR loosening which,
strangely enough, only depict the QR in two of its extreme
positions: tight, and so loose as to either open or turn as
one watches. Isn't it interesting that for these people who
claim to have investigated the issue, that the process of
loosening has never been observed? Especially since it isn't
difficult to accomplish, eg by marking QR knobs against the
fork and regularly checking, which I'm performing at the
moment (and finding no movement as of yet)?

> Let's hear what you imply you know about this and are
> keeping secret.

No secrets. What I imply is that for those who are so
convinced of the QR loosening mechanism as you explain it,
nothing short of a scientific test which investigates this
mechanism is required to prove it. It is a different
scenario to the ejection force that disc brake equipped
front forks suffer from; this is quite easily verified,
analysed and observed.
post #64 of 402

Re: "Actually you are the first person to bring up this issue"

Jose Rizal writes:

>> Let's hear what you imply you know about this and are
>> keeping secret.

> No secrets. What I imply is that for those who are so
> convinced of the QR loosening mechanism as you explain it,
> nothing short of a scientific test which investigates this
> mechanism is required to prove it. It is a different
> scenario to the ejection force that disc brake equipped
> front forks suffer from; this is quite easily verified,
> analysed and observed.

Again, how do you explain the many reports of loosening QR's
with disc brake equipped bicycles? Stop hacking on what
others said and propose some alternative... other than
suddenly many riders don't know how to close a QR.

Jobst Brandt jobst.brandt@stanfordalumni.org
post #65 of 402

Re: "Actually you are the first person to bring up this issue"

In article <fx07c.17600$Cf3.3839@lakeread01>,
"tcmedara" <tcmedara@REMOVEhotmail.com> wrote:

> jobst.brandt@stanfordalumni.org wrote:
> > Tim McNamara writes:
> >
> >
> > Brake forces and their reactions are apparently to
> > complex to be discussed among bicyclists who believe
> > anything bought in a bicycle shop is safely designed.
> >
> > http://www.ne.jp/asahi/julesandjames...disk_and_quic-
> > k_release/
> >
>
> I don't think that at all, but I'm also not going to
> condemn a product or indict an entire industry as a result
> of some line drawings and vector calculations. Apart from
> some internet anecdotes and urban legend, I've yet to see
> anything remotely resembling evidence of a threat to the
> public safety. To illustrate, my lovely wife subscribes to
> the CPSC mailing list. We receive an email nearly ever day
> listing between 1 and 5 different product recalls. These
> recalls typically describe what is often potential flaws
> and possible dangers -- many of which are damn near
> laughable but still result in a recall:
>
> Here's a few examples: http://tinyurl.com/223qd
> http://tinyurl.com/2n2sn
>
> Surf the site and ask yourself if the CPSC is going to
> overlook the disk brake risk when bicycle product recalls
> are issued for injuries no more severe than a broken
> finger. http://tinyurl.com/3yxvb

Well, actually these sound like really damn' obvious
problems! To those who didn't surf the links, here's what's
described:

Item 1: a bike pump that under certain circumstances will
fire the pump handle upwards under pressure. In one case,
hard enough to chip a tooth. That's pretty bad!

Item 2: a helmet that failed the CPSC-standard impact
test. That seems to strike at the heart of the purpose
of a helmet.

Item 3: "The stems on these bicycles can loosen during use."
I think we can agree that's a really big deal, eh?

> I'm the last person to believe the government (US or
> anywhere else) ought to be the ever protective nanny, and
> I'm not suggesting that if the CPSC isn't interested than
> there's no problem. I'm merely illustrating that the idea
> of a huge conspiricy to cover up the problems, and a
> tremendous lack of hard evidence suggests the "problem"
> exists in the realm of the theoretical only.

The problem is that the practical evidence of failures is
buried in the fuzz of other quick-release failure modes. We
know that people forget to tighten QRs on their own fairly
often, so whenever a report is heard of a wheel ejecting,
the natural response is "oh, they probably didn't close the
QR properly before they started riding."

And since there's no way to prove after the fact that you
really are the most obsessive rider in the world about QR
security, there's an obvious suggestion as to how these
accidents do get buried in the statistical fuzz.

Ironically, we may see fewer reports of spontaneous QR
failure as time goes on, because the industry trend is
towards non-dropout axle retainers (QR20 or through-axle
designs) on the types of bikes most likely to have disc
brakes. This is being done to make the front end stiffer and
stronger for unrelated reasons, but by a happy accident also
cures this problem.

--
Ryan Cousineau, rcousine@sfu.ca
http://www.sfu.ca/~rcousine/wiredcola/ President, Fabrizio
Mazzoleni Fan Club
post #66 of 402

Re: "Actually you are the first person to bring up this issue"

"James Annan" <still_the_same_me@hotmail.com> wrote in
message news:405cc1bd$0$23533$44c9b20d@news3.asahi-
net.or.jp... <snip>

> ........who prefer to piss and moan on usenet than
> actually _do_ anything.
>
What, like ride??
post #67 of 402

Re: "Actually you are the first person to bring up this issue"

jobst.brandt@stanfordalumni.org:

> Jose Rizal writes:
>
> >> There's much evidence that discs loosen QRs, and it's
> >> obvious that the forces of the brake try to eject the
> >> front wheel.
>
> > These are two separate issues which must be tackled
> > separately. The latter is obvious, can be easily shown
> > by force analysis and simple test that anyone can do,
> > and requires no further proof. However, there aren't
> > "much evidence" that disc brakes loosen QRs. There are a
> > lot of anecdotes and theorising, but no solid proof.
>
> We don't all need to go to the moon to agree with what
> scientists on earth theorized before astronauts
> verified it.

Not all of us, but astronauts did need to go to verify the
theory. Where are the astronauts in this case?

> Consider that both fork legs carry a vertical load and a
> horizontal load from braking. In addition the leg with the
> disc brake caliper has a torque equal to the total brake
> force times the radius of the wheel applied to its end.
> This differential cases a differential twist of the fork
> dropouts that can incrementally unscrew the QR.

The operative word being "can". The only ways the QR knobs
can move are if the skewer is moved, or if there is a force
applied directly to the QR knobs such that they are
displaced from their position; twisting of the dropout
surfaces the knobs are in contact with can do this, but
consider that since the QR knobs are able to swivel about
the skewer ends by a considerable amount (the lever end is a
loose pivot, the threaded end swivels because of the
threads), the dropouts will have to twist quite considerably
indeed for the QR knobs to be dislodged by this method. It's
unlikely to have this significant twisting of the fork body
without having adverse effect on fork operation, something
that no disc brake operator complains about.

> This effect together with vertical motion of the brake
> side of the axle is the mechanism that can unscrew a QR.
> In some cases this can make the thread tighten and loosen,
> in others it can cause a loosening creep.

So where is the evidence of significant axle movement on the
inner surfaces of dropouts, necessary in order for the axle
to come into contact and move the skewer in the presence of
an annular gap between them?

> In any case, loosening QR's was not a problem before
> widespread disc brake use. This sounds like cracked rims
> all over again.

You don't know this. Your guilt by association is
unconvincing.
post #68 of 402

Re: "Actually you are the first person to bring up this issue"

Ryan Cousineau:

> > Maybe, but you can bet money that the "new" radial
> > designs will not be relying on bolts' threads taking up
> > the loads in tension.
>
> Right. But are "Manitou" mounts on bike brakes (that is,
> the equivalent of these radial mounts) really overloading
> the threads? That's a design error, from beginning to end.
> If the bolt isn't preloaded, it doesn't really do what a
> bolt should. Once preloaded, bolts do a very good job of
> holding things together. Well, until they're overloaded.

Bolt preloading isn't relevant here. The post style
"Manitou" mounts behind the fork do not put any tensile
loads on the mounting bolts. Most of the load is taken up by
the posts in compression, with the mounting bolts taking up
a component of the caliper braking force in shear. Putting
the posts in front of the fork will result in the bolts
taking up the bulk of the caliper braking force in tension,
which means you're relying on the threads on both the bolts
and the posts to prevent the bolts from being pulled out.
Sure you can design for larger bolts that can withstand
caliper braking forces in tension, but why do this when you
end up with unnecessarily bulkier and heavier mounts?
post #69 of 402

Re: "Actually you are the first person to bring up this issue"

> Again, how do you explain the many reports of loosening
> QR's with disc brake equipped bicycles? Stop hacking on
> what others said and propose some alternative... other
> than suddenly many riders don't know how to close a QR.

It's curious that you assume that they do. Is there
something about the mtn biking crowd that's more educated
and technical than roadies? I rarely find people tightening
up their QRs on road bikes as tight as they should be,
particularly on the front. While I treat them with disdain,
I have to admit that "lawyer lips" probably have saved a
good many people from serious accident & injury.

--Mike-- Chain Reaction Bicycles
http://www.ChainReactionBicycles.com

<jobst.brandt@stanfordalumni.org> wrote in message
news:TG77c.940$Fo4.8984@typhoon.sonic.net...
> Jose Rizal writes:
>
> >> Let's hear what you imply you know about this and are
> >> keeping secret.
>
> > No secrets. What I imply is that for those who are so
> > convinced of the QR loosening mechanism as you explain
> > it, nothing short of a scientific test which
> > investigates this mechanism is required to prove it. It
> > is a different scenario to the ejection force that disc
> > brake equipped front forks suffer from; this is quite
> > easily verified, analysed and observed.
>
> Again, how do you explain the many reports of loosening
> QR's with disc brake equipped bicycles? Stop hacking on
> what others said and propose some alternative... other
> than suddenly many riders don't know how to close a QR.
>
> Jobst Brandt jobst.brandt@stanfordalumni.org
post #70 of 402

Re: "Actually you are the first person to bring up this issue"

James Annan <still_the_same_me@hotmail.com> wrote:
> tcmedara wrote:
>
>
>> I don't mean well at all. I responded 'cause I find humor
>> in pointing out logical inconsistency. I didn't "realise"
>> you'd contact anyone because you rejected the notion as
>> not worthwhile. I'm pretty intelligent, but not
>> clairvoyent. I could have realized it had you bothered to
>> mention it.
>
> If you had glanced at the website you would have seen. In
> fact, anyone coming new to the debate who thinks they have
> some startling insight should probably read it. My
> dealings with the CPSC are detailed at
>
> http://www.ne.jp/asahi/julesandjames...sk_and_quick_-
> release/cpsc.html
>
> and you might learn something from the related pages too.

If you want to make a point, then make the point. Don't
force me to surf your silly site to divine what you may or
may not have done. However, I have now looked at the web
site, full of assertion, anecdote, and conspiracy theories.
A good read, though
>
>>> As for J DeMarco at the CPSC, well he commissioned Mark
>>> LaPlant of Cannondale to report on the issue, and
>>> surprisingly enough the turkey didn't vote for
>>> Christmas. In fact he produced a bull**** whitewash
>>> which he refuses to publish. But since all the
>>> manufacturers can (apparently truthfully) claim that no
>>> rider has ever reported any incident, there really is
>>> little more that the CPSC can (or probably should) do.
>>
>>
>> Again, not the "truth" you espouse so therefore it's a
>> "whitewash". Next you're going to tell us the CIA is
>> behind it all right? Ya know, if you could document
>> actual circumstances (rather than internet anecdotes and
>> gossip), than you could prove the point to the apparently
>> intransigent CPSC.
>
> I suggest you read the letters I've posted on that page,
> and try to work out a plausible explanation for his
> behaviour.

The letters don't mean much. I could search out thousands of
posts in these NGs alone where riders will proclaim years of
use with nary a problem. Do those matter? How's this for an
explanation: He investigated the issue, found nothing to
worry about, and has written you off. Maybe you strike him
as one of probably millions of consumers with an axe to
grind on the hazards of "product x". Having covered the
issue already, he's probably not interested in dealing with
it anymore. Maybe it was cutting into his biking time.
>
> A quick summary:
>
> I emailed DeMarco several times in August and September,
> and was repeatedly told that a letter was on its way, or
> had even been sent. Eventually I got a bland Word document
> as an email attachment.

Bland? What did you expect from a buearucrat?
>
> In mid October, I received the official letter which was
> significantly different. Although dated 2 Sept, it was
> only posted on the 15th October, a couple of days _after_
> the ASTM meeting to which it refers.
>
> DeMarco has not replied to any of my emails since that
> date. Mark Laplant refuses to publish his report which was
> presented at the "open" ASTM meeting.

I'd be interested to see your emails to him. I'm wondering
if that might explain how you ended up in his killfile. And
while Laplant "refuses" to publish his report, can't you at
least give us a synopsis of what he presented? You call it a
whitewash, but offer no content. Has anyone actually
requested that he publish the report? Are there any policies
that require him to do so, either by the CSPSC or the ASTM.
If it was done at the request of the CPSC it should be
available via a FOIA request. Have you tried that? Or does
self-righteous indignation render such details irrelevent?

>
> Ask them yourselves if you don't believe me. Oh, I forgot,
> you're one of those who prefer to piss and moan on usenet
> than actually _do_ anything.

I'm not "pissing an moaning", I'm chuckling. Check the
thread dude....yours is the original post, and it's pretty
much a piss and moan from the outset. I'm merely
participating in a discussion on usenet. I do it for fun and
amusement, not to evangalize. I'm not the one who's
advocating an issue, you are. I'll do something when it
needs doing. Are you upset because I've failed to heed your
call to arms? What would you have me do? Let me give you a
hint: If you're looking to _do_ something, or prod others to
do it, then usenet ain't the place to be. People come here
to debate, chat, share, discuss, joke, and argue -- not to
"do" anything.

See my response to Jobst Brandt elsewhere in this thread.
I'm not doubting the physics or the mechanism you describe,
I'm just doubting that it's quite the problem you espouse.
Is a potential problem that fails to materialize really a
problem at all? Like I asked Jobst: Is this really a problem
in the empirical world, or just another reason to check your
QR before you ride? I know *your* answer, but it seems it's
not so certain in the minds of many others.

Tom
post #71 of 402

Re: "Actually you are the first person to bring up this issue"

Ryan Cousineau <rcousine@sfu.ca> wrote:
> In article <fx07c.17600$Cf3.3839@lakeread01>,
> "tcmedara" <tcmedara@REMOVEhotmail.com> wrote:
>
> Well, actually these sound like really damn' obvious
> problems! To those who didn't surf the links, here's
> what's described:
>
> Item 1: a bike pump that under certain circumstances will
> fire the pump handle upwards under pressure. In one case,
> hard enough to chip a tooth. That's pretty bad!
>
> Item 2: a helmet that failed the CPSC-standard impact
> test. That seems to strike at the heart of the purpose of
> a helmet.
>
> Item 3: "The stems on these bicycles can loosen during
> use." I think we can agree that's a really big deal, eh?
>
My point was that the CPSC would issue recalls for bicycle
components, even based on minor or even potential injury.
I'm merely asking the question of why, in light of the
propensity for the CPSC to protect us from relatively minor
risks, would they dismiss the disk/qr issue so readily?
>
> The problem is that the practical evidence of failures is
> buried in the fuzz of other quick-release failure modes.
> We know that people forget to tighten QRs on their own
> fairly often, so whenever a report is heard of a wheel
> ejecting, the natural response is "oh, they probably
> didn't close the QR properly before they started riding."
>
> And since there's no way to prove after the fact that you
> really are the most obsessive rider in the world about QR
> security, there's an obvious suggestion as to how these
> accidents do get buried in the statistical fuzz.

So you're saying there's no way to know if the disk/qr issue
is really a risk in light of all the other qr related
hazards out there. This makes a great argument to redesign
the quick release, regardless of the type of braking system
used. It also points to what I've been saying all along --
There's really no way to determine if the potential disk
brake/qr problem actually translates into real problems on
the trail. Assuming it's the disk design, even as a prudent
measure, could actually result in failure to detect the
likely cause of wheel releases. Maybe there's just a bunch
of crappy QRs out there that shouldn't be on any bike. If
it's buried in the statistical fuzz, then there's no way to
draw conclusions.
>
> Ironically, we may see fewer reports of spontaneous QR
> failure as time goes on, because the industry trend is
> towards non-dropout axle retainers (QR20 or through-axle
> designs) on the types of bikes most likely to have disc
> brakes. This is being done to make the front end stiffer
> and stronger for unrelated reasons, but by a happy
> accident also cures this problem.

I gotta agree there. Take the guess work right out of it and
mitigate lots of risk from a variety of real and potential
sources. I do like that QR though....

Tom
post #72 of 402

Re: "Actually you are the first person to bring up this issue"

jobst.brandt@stanfordalumni.org:

> Jose Rizal writes:
>
> >> Let's hear what you imply you know about this and are
> >> keeping secret.
>
> > No secrets. What I imply is that for those who are so
> > convinced of the QR loosening mechanism as you explain
> > it, nothing short of a scientific test which
> > investigates this mechanism is required to prove it. It
> > is a different scenario to the ejection force that disc
> > brake equipped front forks suffer from; this is quite
> > easily verified, analysed and observed.
>
> Again, how do you explain the many reports of loosening
> QR's with disc brake equipped bicycles? Stop hacking on
> what others said and propose some alternative... other
> than suddenly many riders don't know how to close a QR.

If anyone's doing any hacking, it's you. I notice you
conveniently ignored the postulations that I put forward,
preferring instead to stomp your foot down and sulk. For one
thing, you assume but you really don't know that there are
many more QRs loosening with disc brakes than with rims.
Your basis for your belief in your theory of QRs loosening
hinges on this assumption, yet you've shown no statistical
surveys that prove this nor any evidence which support it.

For another, the so-called observations of QRs loosening is
a misnomer; people have observed tight and loose QRs but no
one has seen it go from tight to loose; in other words, your
theory is unproven and unobserved, your evidence
circumstantial.
post #73 of 402

Re: "Actually you are the first person to bring up this issue"

Jose Rizal wrote:
> jobst.brandt@stanfordalumni.org:
>
>
>>Jose Rizal writes:
>>
>>
>>>>Let's hear what you imply you know about this and are
>>>>keeping secret.
>>
>>>No secrets. What I imply is that for those who are so
>>>convinced of the QR loosening mechanism as you explain
>>>it, nothing short of a scientific test which investigates
>>>this mechanism is required to prove it. It is a different
>>>scenario to the ejection force that disc brake equipped
>>>front forks suffer from; this is quite easily verified,
>>>analysed and observed.
>>
>>Again, how do you explain the many reports of loosening
>>QR's with disc brake equipped bicycles? Stop hacking on
>>what others said and propose some alternative... other
>>than suddenly many riders don't know how to close a QR.
>
>
> If anyone's doing any hacking, it's you. I notice you
> conveniently ignored the postulations that I put forward,
> preferring instead to stomp your foot down and sulk. For
> one thing, you assume but you really don't know that there
> are many more QRs loosening with disc brakes than with
> rims. Your basis for your belief in your theory of QRs
> loosening hinges on this assumption, yet you've shown no
> statistical surveys that prove this nor any evidence which
> support it.
>
> For another, the so-called observations of QRs loosening
> is a misnomer; people have observed tight and loose QRs
> but no one has seen it go from tight to loose; in other
> words, your theory is unproven and unobserved, your
> evidence circumstantial.
>

So just for my sanity do you suggest that a well-tightened
XT hub/skewer combo should be safe?

Greg
post #74 of 402

Re: "Actually you are the first person to bring up this issue"

G.T.:

> So just for my sanity do you suggest that a well-tightened
> XT hub/skewer combo should be safe?

I'm suggesting that you mark your "adequately" tightened
front QR against the fork and observe it regularly. If true,
and since the QR-loosening-by-disc-braking proponents agree
that it's unlikely to be a catastrophic event but rather the
accumulation of many cycles of brake loading, you should be
able to observe its progress if you're vigilant enough.
post #75 of 402

Re: "Actually you are the first person to bring up this issue"

"Nelson Binch" <stopthevirus@prodigy.net> wrote in message
news:c2D6c.37209$bW4.16813@newssvr16.news.prodigy.com...
> Cross posts I don't participate in removed.
>
> "James Annan" <still_the_same_me@hotmail.com> wrote in
> message news:405aed81$0$23537$44c9b20d@news3.asahi-
> net.or.jp...
> > It's now a year since the QR/disk brake problem hit the
> > headlines, and I thought some of you might be interested
> > in hearing how the manufacturers are dealing with it.
> >
>
> Wow! How many people are having this problem? Out of how
> many disk
users?
>
> Sorry, but every single time I've seen pictures of these
> 'incidents' it looks like improperly set skewers to me.
>
>

It's much easier to blame the user. That's what you're doing
and that's what the manufacturers are doing. Even though
they know the forces acting to rip the wheel out of the
dropout are high.

Greg
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