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

Tom Medara writes:

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...quick_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.

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.

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.

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.

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.

You are making this a "huge conspiracy" as a straw man to discredit a
fact discovered that most people have not been perceptive enough to
recognize.

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?

Jobst Brandt

On Sat, 20 Mar 2004 11:17:36 -0500, "tcmedara"
wrote in message
27_6c.17111$Cf3.3567@lakeread01:

Dumabass, Frobnitz was *supporting you* !
Yeah, I realised that. I guess humo(u)r doesn't travel well.
Perhaps you should give it up for something you're better at...

James was using irony, and using it rather well. Eddie (Frobnitz)
"gets" irony, based on past exchanges.

--
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

On Sat, 20 Mar 2004 00:13:45 -0600, Tim McNamara
wrote in message
:

Putting the caliper on the front of the fork would probably lead to
it ripping off it's mounting.

How do you figure? The forces on the mounting bosses on the fork leg
would be the same as they are with the current design.

In one case the welds are in tension, in the other, in compression. I
don't think it would make much odds, as I suspect the welds are more
than strong enough anyway, but I've been wrong before.

Changing the angle of the dropout would also work and probably cost
less.

--
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

On Sat, 20 Mar 2004 14:01:38 -0500, "tcmedara"
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

"tcmedara" wrote in message
news:eQZ6c.17050$Cf3.10186@lakeread01...
Not sure why you feel the need to resort to silly euro-trash snobbery for
a
cheap joke. Check back on my original post and you'll see it had a good
amount of irony and sarcasm, all meant to find humor in the gyrations of
the
obsessed, sorry you were too wrapped up in your own prejudices to get it.
Perhaps it was too sophisticated for your worn, tired, uk-centric world
view
(see, it works both ways...) Thankfully most of your countrymen aren't
quite provincial. I would have goofed on anyone who posted similar tripe,
regardless of nationality.

The good Mr Annan can claim his knee-jerk defensiveness was an attempt at
humor, but I don't buy it. Taken in the context of his other posts, I'm
not
sure why one is supposed to view that through a humo(u)rous lense while
taking him seriously in all the others. Taken at face value, he's just
plain full of ****. He rejects the notion of contacting an agency who can
*do* something about the perceived problems, then retorts that he tried
and
failed. Methinks he may want to recheck his facts or re-evalute the
veracity of his opinion. Looks like the laugh's on you.

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

writes:

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.

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..

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.

"Just zis Guy, you know?" writes:

On Sat, 20 Mar 2004 00:13:45 -0600, Tim McNamara
wrote in message
:

Putting the caliper on the front of the fork would probably lead
to it ripping off it's mounting.

How do you figure? The forces on the mounting bosses on the fork
leg would be the same as they are with the current design.

In one case the welds are in tension, in the other, in compression.

Try diagramming out the forces. You'll see that they work out to be
about the same whether the brake is in front of or behind the fork
leg.

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...ease/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 **** and moan on usenet than actually _do_ anything.

James

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.


Jobst Brandt



I done this test (by accident) before this whole issue ever surfaced.
Indeed, it does want to pull out, which only proves "our" point; An
improperly installed front wheel (disc + QR) is a very, very dangerous
thing.

So what's your point again?
--
Slacker - been DH'ing w/6" rotors on QR front wheel for the past 2 yrs

in message fx07c.17600$Cf3.3839@lakeread01, tcmedara
') 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 Brooke) http://www.jasmine.org.uk/~simon/

;; single speed mountain bikes: for people who cycle on flat mountains.