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"Actually you are the first person to bring up this issue" - Page 4

post #46 of 402

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

G.T.:

> 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.

> When I tighten something, I expect it to stay tight. But
> I'll be checking my QRs mid-ride these days, and someday
> I'll be buying a through-axle fork.

Do that and log the number of times you find your front QR
loose because of disc braking. A reliable way of doing this
is marking your QR knobs against the fork with a marker
after adequate tightening, and checking regularly to see if
these remain aligned.
post #47 of 402

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

On Sat, 20 Mar 2004 14:01:38 -0500, "tcmedara"
<tcmedara@REMOVEhotmail.com> wrote in message
<fx07c.17600$Cf3.3839@lakeread01>:

>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.

Then try this simple test: take two bikes, one with rim
rakes and one with discs. Loosen the QR. Ride forward.
Brake. See which wheel jams.

In the case of the disc braked wheel the twisting of the
axle due to braking forces can actually cause it to jam at
walking speed with the QR loose, according to my admittedly
unscientific test. And we all know that QRs can - and do -
pop open completely, on occasion.

A brake which tends to remove or jam the wheel on
application, and which is only controlled by constantly
checking tightness of the QR, is, in my view,
inherently unsafe.

And yes, I do have a bike with front discs. I use allen-key
QRs and check them frequently.

--
Guy
===
May contain traces of irony. Contents liable to settle after
posting. http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at
Washington University
post #48 of 402
Thread Starter 

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

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..._and_quick_re-
lease/cpsc.html

and you might learn something from the related pages too.

>>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.

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.

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.

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.

James
post #49 of 402

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

Jose Rizal wrote:
> G.T.:
>
>> 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.
>
>> When I tighten something, I expect it to stay tight. But
>> I'll be checking my QRs mid-ride these days, and someday
>> I'll be buying a through-axle fork.
>
> Do that and log the number of times you find your front QR
> loose because of disc braking. A reliable way of doing
> this is marking your QR knobs against the fork with a
> marker after adequate tightening, and checking regularly
> to see if these remain aligned.

What is the point of advising that? You would just call it
another "anecdote". It's already been done and QRs have been
observed to rotate. See http://www.ne.jp/asahi/julesandjame-
s/home/disk_and_quick_release/index.htm l

~PB
post #50 of 402

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

Tim McNamara:

> Jose Rizal <_@_._> writes:
>
> > G.T.:
> >
> >> 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.
>
> There has been some published evidence in trade magazines
> that this does in fact happen. ISTR that the material has
> been quoted or paraphrased at VeloVision (the trade
> magazine and Website not being available to the general
> public). It's not overwhelingly great evidence at this
> point, as I recall. But it's some data at least.

I still fail to see the veracity of the mechanism proposed
for QR loosening with disc brakes. If you look at one of
your QR hubs, you'll see that the QR skewer is loose within
the hub axle. For an XT hub this annular gap can be a
maximum of about 1mm. When the axle is snug against the
dropout, and the QR is tightened, the skewer and the axle do
not form a directly connected unit. Very small movements of
the axle will not necessarily move the skewer itself because
of this annular gap. At the worst case, the axle will have
to move radially by about 1mm to touch the skewer, and move
just a bit more than that to move the skewer as well. The
axle will then have to move back by more than a mm to push
the skewer back as well. In other words, the axle will have
to have a cyclic movement of over plus and minus 1mm
amplitude in order to affect the skewer, to which the QR
knobs are connected. Cyclic movement by the axle of this
magnitude will be quite noticeable. It will also be quite
obvious if the axle moves so significantly when the inside
surface of the dropouts are examined. There hasn't been any
mention of this that I've seen anywhere. Hence I see a need
for scientific testing of this mechanism.
post #51 of 402

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

in message <fx07c.17600$Cf3.3839@lakeread01>, tcmedara
('tcmedara@REMOVEhotmail.com') wrote:

> Hell, I don't even ride with disks and I think the whole
> debate is a crock.

Says it all, really. If you did, you wouldn't.

Mind you, of course, a through axle solves all the problems,
and a monoblade pretty much has to have a through axle, so
there's yet another reason to go monoblade...

--
simon@jasmine.org.uk (Simon Brooke)
http://www.jasmine.org.uk/~simon/

;; single speed mountain bikes: for people who cycle
on flat mountains.
post #52 of 402

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

Pete Biggs:

> >> When I tighten something, I expect it to stay tight.
> >> But I'll be checking my QRs mid-ride these days, and
> >> someday I'll be buying a through-axle fork.
> >
> > Do that and log the number of times you find your front
> > QR loose because of disc braking. A reliable way of
> > doing this is marking your QR knobs against the fork
> > with a marker after adequate tightening, and checking
> > regularly to see if these remain aligned.
>
> What is the point of advising that? You would just call it
> another "anecdote". It's already been done and QRs have
> been observed to rotate. See http://www.ne.jp/asahi/jules-
> andjames/home/disk_and_quick_release/index.htm l

Show me exactly where someone has done what I stated,
because I don't see it. The "anecdotes" consist of people
looking down to see their QR already loose and rotating
(there are many causes for this, who knows what happened),
or one guy who thinks his QR got loose because he opened and
closed them before and after some rides and he "felt" they
were looser. My suggestion is a lot less subjective and one
of the easiest things to do. It also lends itself to
observation of a gradual progression of loosening. Isn't it
strange that these "anecdotes" seem to consist only of
observations on either end of the spectrum, that the QR is
tight at the beginning , and the QR is already loose or
open/turning. The method I suggest will show the stages in
between, and will confirm if it's the cyclic loading of the
axle that is the cause.

Yes, I'm currently doing this on my QR and disc-equipped
bike, and have yet to see any movement of the QR knobs.
post #53 of 402

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

Jon Senior <jon@restless_REMOVE_lemon.co.uk> wrote:
>
> I've included the entire text of your post, untroubled by
> intruding comments because it is so funny I felt it should
> appear again. OK. You didn't get the joke. That's fine.
> It's nothing (much) to be ashamed of. It does seem that
> everyone else did however.
>
> And frankly, the idea that because someone was serious
> in the past, prevents them from being humourous now is
> preposterous. Can a stand-up comedian raise a serious
> point? Could a mortician say something funny? (I
> believe it was called "Six-feet Under", although I
> sadly missed it!)
>
> Get out more. Get on your bike and burn off some of
> that bile.
>
> "Have a nice day!"
>
> Jon

Obviously you don't get the point either, Jon. I caught the
sarcasm in Annan's post from the outset. My point was that
it was utterly defensive and misdirected in light of the
suggestion to contact an advocacy group. I concur, people
can easily switch between serious discussion and humor.
However I don't often see someone zealously espousing a
crusade and then turn to self-effacing humor on the same
topic. Smacks of schizophrenia to
me....

I'd love to go out and ride, but injury prevents that.
Bile's all I've got for the moment (<----sarcasm)

Tom
post #54 of 402

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

> Brake forces and their reactions are apparently too
> complex to be discussed among bicyclists who believe
> anything bought in a bicycle shop is safely designed.
>
> http://www.ne.jp/asahi/julesandjames...sk_and_quick_-
> release/
>
> Jobst Brandt jobst.brandt@stanfordalumni.org
>

Wow, Jobst usually doens't jump on a band wagon 6 years too
late. Getting old I guess.
--
_________________________
Chris Phillipo - Cape Breton, Nova Scotia http://www.ramsays-
online.com
post #55 of 402

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

> > I'd have thought angling the drop-out so it faces
> > forward would prevent the axle rotating out if the
> > pads are the pivot point. I'm still trying to think of
> > any negative implications from doing this as it seems
> > too easy.
>
> Changing the dropout angle or created enclosed dropouts
> like motorcycles use would be one solution.

Which they have done, us XCers simply won't buy it due to
the extra weight. If you are doing free ride or DH with a
single crown fork/regular QR axle for these days you pretty
much desserve what you get.

--
_________________________
Chris Phillipo - Cape Breton, Nova Scotia http://www.ramsays-
online.com
post #56 of 402

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

In article <bs07c.883$Fo4.8423@typhoon.sonic.net>,
jobst.brandt@stanfordalumni.org says...
> anonymous snipes:
>
> > The bottom line here is not whether or not this issue is
> > truthful, but how and why it happens. I for one would
> > like to know what the circumstances are in each case
> > that may trigger it.
>
> > So the question is this: in each case where the problem
> > occured, what were the conditions? was it human error,
> > or part failure?
>
> How about doing a test that takes about 30 seconds. Open
> the QR on a disc brake equipped front wheel. Push the
> bicycle forward and notice what the axle does.
>
> 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.
>
> The point is that the wheel should not have disengaging
> forces while braking. These would not occur if the caliper
> were mounted in front of the fork.
>
> Jobst Brandt jobst.brandt@stanfordalumni.org
>

Of course then the caliper would tear off much as it
does not on the rear for people doing trials riding
where the rear wheel is pulling in the opposite
direction that was intended.
--
_________________________
Chris Phillipo - Cape Breton, Nova Scotia http://www.ramsays-
online.com
post #57 of 402

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

> >
>
> Of course then the caliper would tear off much as it does
> not on the

not=now

--
_________________________
Chris Phillipo - Cape Breton, Nova Scotia http://www.ramsays-
online.com
post #58 of 402

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

Tim McNamara writes:

>>>> I keep hearing about this issue with greater frequency,
>>>> but I've been running discs for a few years now and
>>>> it's only popped out once in that time. It was my fault
>>>> on that occasion, I realized afterwards that I hadn't
>>>> properly tightend the QR.

>> What means "properly tightened"?

> Just to point out, Jobst, that that's a misattribution. I
> didn't write that. So I can't answer your question.

Tim! There were three >>> ahead of that statement, therefore
obviously not from you. I assumed readers understand the
notation of included prior text, common on this medium.

>>> See, that's the point. The brake should be designed so
>>> that it *can't* force the wheel out of the dropouts,
>>> even if the QR is left completely loose. It's a design
>>> flaw, an epic design flaw that will cost some
>>> manufacturer a *lot* of money in court some day. No
>>> other current brake design that I'm aware of puts an
>>> ejection force into the wheel in normal operation, but
>>> front disk brakes do.

> I wrote the above, though, and thus am responsible for any
> errors, misconceptions or rank stupidity it may contain..

Again, it having only two >> at the time you read it it must
have been from you.

>> Hold it! Even though this has been discussed at great
>> length here in wreck.bike, it appears to me that most of
>> the respondents did not understand that a disc caliper
>> behind the fork causes a wheel disengaging force, and
>> that repeated braking WILL loosen a QR.

> Umm, yes, I do understand that model in concept. Just
> didn't mention it in this paragraph as I was focusing on
> the fundamental problem that disc brakes create an
> ejection force in the first place, and not commenting on
> the progressive unscrewing of the QR from repeated
> application of that ejection force.

>> Therefore, with the majority of contributors resting in
>> the "James Annan is all wrong" boat what you just posted
>> gets us back to the start, a few hundred responses ago.

> Hmm. Thought I was agreeing with Annan. Somehow it got
> construed that I don't.

You were but the consensus here seems to be opposed to that
preconception and that is what I stated.

Jobst Brandt jobst.brandt@stanfordalumni.org
post #59 of 402

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

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

Jobst Brandt jobst.brandt@stanfordalumni.org
post #60 of 402

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

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.
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. 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.

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

Jobst Brandt jobst.brandt@stanfordalumni.org
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