Cannondale's tests of disks and QRs

jim beam wrote:

well, let's put this into perspective.


http://groups.google.com/groups?selm...&output=gplain

bleating about risk of ejection is like bleating about brake cable
being
at risk of pull-through at the clamping point - exactly the same
principle applies.

Not really. If your front brake fails you still have a back brake and can
put a foot down. If your front wheel ejects, you are headed for the ground
head first and there is nothing you can do about it.

if the force generate by braking is 1/3 that of
the force necessary to cause slippage [ignoring of course lawyer
lips], then
i can't see what the fuss is about. 1/3 of yield is a well accepted
margin.

But you don't know that it is, because nobody has seriously tested the
proposition (or the possible loosening effect of repeated braking on rough
ground).

personally, i'd be more worried about hydraulic hose failure or brake
levers fatiguing than axle slippage.

I wouldn't, because as long as the bike remains in one piece you have some
options to get off without briefly experiencing unpowered flight.

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

Just zis Guy, you know? wrote:
jim beam wrote:


well, let's put this into perspective.


http://groups.google.com/groups?selm...&output=gplain


bleating about risk of ejection is like bleating about brake cable
being
at risk of pull-through at the clamping point - exactly the same
principle applies.


Not really. If your front brake fails you still have a back brake and can
put a foot down. If your front wheel ejects, you are headed for the ground
head first and there is nothing you can do about it.


if the force generate by braking is 1/3 that of
the force necessary to cause slippage [ignoring of course lawyer
lips], then
i can't see what the fuss is about. 1/3 of yield is a well accepted
margin.


But you don't know that it is, because nobody has seriously tested the
proposition (or the possible loosening effect of repeated braking on rough
ground).

who says it's not been tested? just because it's not found it's way
onto r.b.t. doesn't mean that it's not been considered. if i were a
manufacturer, i'm _certain_ i wouldn't want to get sucked into ****ing
matches on this forum. when's the last time we heard from damon rinard,
tom ritchey, whoever? bitterness and negativity serves no purpose other
than to convince the people that /do/ know what they're talking about
that they're casting pearls before swine.

getting back to your point, i've seen no evidence that qr's loosen in
service. they have nylock thread locks and serrated thumbscrews. what
else would be necessary? can't say i've seen anyone post evidence of it
here either. if you've seen it, post a link so we can check it out.
imo, the "loosening" argument just a weak supposition to save face when
confronted with fact.

as for ejection, if you're worried about it, buy a downhill fork. it's
not like they're no an option!



personally, i'd be more worried about hydraulic hose failure or brake
levers fatiguing than axle slippage.


I wouldn't, because as long as the bike remains in one piece you have some
options to get off without briefly experiencing unpowered flight.

Guy

depends on environment i guess. where i ride, you would indeed
experience unpowered flight, even if the bike was in one piece. sharp
downhill hairpins with adverse cambers do not allow you to enter a turn
without having controlled your speed first. if you have no brake,
you're out, period. ruined bushes & trees in the impact zone bear
testimony to that.

On Mon, 27 Sep 2004 07:01:25 -0700, jim beam
wrote in message :

if the force generate by braking is 1/3 that of
the force necessary to cause slippage [ignoring of course lawyer
lips], then
i can't see what the fuss is about. 1/3 of yield is a well accepted
margin.

But you don't know that it is, because nobody has seriously tested the
proposition (or the possible loosening effect of repeated braking on rough
ground).

who says it's not been tested? just because it's not found it's way
onto r.b.t. doesn't mean that it's not been considered.

You think they'd keep it quiet if they tested it and found no problem?
Remember, the CPSC have not had any submissions on this either. And
the bike trade press are interested, so you'd expect, if nothing else,
a letter from somoene in the trade to one of the trade mags. Instead
we have silence, except for Cannondale who performed a test which
looks to me to be woefully inadequate.

getting back to your point, i've seen no evidence that qr's loosen in
service. they have nylock thread locks and serrated thumbscrews. what
else would be necessary?

Vibration and twisting forces on the wheel causing oscillations in the
skewer tension. Just like any other threaded fastener. See James'
pages for an explanation of the proposed mechanism.

http://www.ne.jp/asahi/julesandjames...se/#unscrewing

as for ejection, if you're worried about it, buy a downhill fork. it's
not like they're no an option!

Really? Where do I get a lightweight downhill fork for an ETRTO 406
wheel? But you miss the point: if the downhill fork is necessary,
then there is a problem!

personally, i'd be more worried about hydraulic hose failure or brake
levers fatiguing than axle slippage.

I wouldn't, because as long as the bike remains in one piece you have some
options to get off without briefly experiencing unpowered flight.

depends on environment i guess. where i ride, you would indeed
experience unpowered flight, even if the bike was in one piece.

So you think that a front wheel ejecting is no more likely to cause
you to land head first than any other component failure? That's an
odd point of view. It sounds like your riding is far from typical.

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

jim beam wrote:


who says it's not been tested? just because it's not found it's way
onto r.b.t. doesn't mean that it's not been considered.

So what do you think about Cannondale's test?

I think you'd better be careful about how much intelligence you
attribute to the manufacturers. If they are stupid, then they are
stupid, but if they are clever, it is hard to avoid the conclusion that
they are dishonest.

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

Just zis Guy, you know? said...

So you don't think a change form a system where there was no force
tending to eject the wheel, to one where there is such a force, and
which has apparently resulted in at least two serious crashes we know
of, leaving at least one man paraplegic, is "any more dangerous than
any other part of the bike?"

I have seen only one accident demonstrated to be due to disc brakes
ejecting a wheel--that of James Annan, and his was a very unusual bike,
to say the least. I do believe that the CPSC would be fully justified in
issuing a recall of forks like his, especially those attached to
tandems, but the rest of us are riding very different bikes and dropping
an a-bomb on the industry is simply not justified.

Last I saw on the web site to benefit Russ Pinder, it was said that the
cause of his accident probably will never be known. Maybe they are
singing a different tune now. That is their business. Are we supposed to
believe that for every bike that loses a wheel and happens to have disc
brakes, that the disc brakes are the cause? Did bikes never lose wheels
before disc brakes? What about vibration, flex and various other
stresses? Couldn't a QR work loose because of something besides a disc
brake?

Cannondale's test looks a lot like "go away and prove that this is not
a problem" rather than "go away and find out what has to be done to
make this problem happen". As an engineer by training, knowing that
the problem almost certainly has happened at least twice, I would be
inclined to take the later approach. As a corporation with potential
lawsuits to consider, I'd maybe take the first option. No I wouldn't,
but I can see why someone else might.

So, the issue still has not been adequately investigated. And none of
us have the cash to do so. Back to square one.

Guy

Much more important than Cannondale's test is the test that many
thousands of riders do each day. This whole scare is like a ghost story.
Certain people claim to have seen it, but when we go looking for it, we
can't find anything.

James Annan said...

The fork is recommended for riders of up to 250 pounds. No, I don't
think it is reasonable to claim that a sub-130 pound rider is committing
"obvious abuse" just by riding such equipment, however skilled they are.
I guess it might be theoretically possible that she was abusing the
equipment, but her riding partner at the time said:

"The goofing around wasn't in the Wade Simmons league either. Just hard
riding."

Do you have a reference for the 250lb limit? I'm not saying you are
wrong but that is generous limit for that type of fork.

Can you suggest something abusive that she might have been doing to
cause a QR failure of any sort?

Jumping? Bombing downhill? If the lightest fork is appropriate for any
use, why have free ride and downhill forks?

In fact, I have admitted from day one that you discovered something

Very gracious of you to say so. All I wanted from the start was an
honest and open treatment of this problem, which may be quite rare but
has undoubtely cause several horriffic crashes which some victims have
been very lucky to survive. I posted one of these links before to a
story about a rider who spent two weeks in a coma, if there hadn't been
an MRT team already called out in the area it might have taken several
hours to get him to hospital and onto a ventilator rather than the
amazing 51 minutes quoted in the second link:

http://www.singletrackworld.com/article.php?sid=1309
http://www.mountainrescue.org.uk/news.html

However, rather than deal with the problem, it seems like the
manufacturers have done everything in their powers to brush it under the
carpet and wish it away. As a result of which, more riders have been
seriously injured, like the one whose email I posted a few days ago.
What would you do in these circumstances? Shrug your shoulders and say
it's not your problem?

James

See my reply Guy above. Every wheel loss is the result of a disc brake
ejection? I quote:

"I shot off in front of the five other guys, they couldn't keep up with
me. I was going over boulders at about 30mph. Then the front wheel fell
off the bike. I landed on my head, shattering my helmet and was
completely out of it."

How is this a definitive case of disc brake wheel ejection? He was
riding like a maniac and lost the wheel. It couldn't possibly be because
he just bounced and jolted it out of its socket? Did something break? I
don't see any indication that he is joining your crusade or that he even
knows anything about it.

Just zis Guy, you know? wrote:

getting back to your point, i've seen no evidence that qr's loosen in
service. they have nylock thread locks and serrated thumbscrews. what
else would be necessary?


Vibration and twisting forces on the wheel causing oscillations in the
skewer tension. Just like any other threaded fastener. See James'
pages for an explanation of the proposed mechanism.

http://www.ne.jp/asahi/julesandjames...se/#unscrewing



Which doesn't answer the question that is perpetually ducked. James'
explanation is based on the Bolt Science article on vibration loosening.
That same article goes on to talk about preventing vibration loosening
and names serratation on the nut, nyloc type friction locking and
loctite type chemical locking as the three recognised preventative
measures. So give that two of these are being used on a standard Shimano
QR, why do you still think it is vibration loosening?

Tony

SuperSlinky wrote:
Just zis Guy, you know? said...


So you don't think a change form a system where there was no force
tending to eject the wheel, to one where there is such a force, and
which has apparently resulted in at least two serious crashes we know
of, leaving at least one man paraplegic, is "any more dangerous than
any other part of the bike?"


I have seen only one accident demonstrated to be due to disc brakes
ejecting a wheel--that of James Annan, and his was a very unusual bike,
to say the least. I do believe that the CPSC would be fully justified in
issuing a recall of forks like his, especially those attached to
tandems, but the rest of us are riding very different bikes and dropping
an a-bomb on the industry is simply not justified.

Last I saw on the web site to benefit Russ Pinder, it was said that the
cause of his accident probably will never be known. Maybe they are
singing a different tune now. That is their business. Are we supposed to
believe that for every bike that loses a wheel and happens to have disc
brakes, that the disc brakes are the cause? Did bikes never lose wheels
before disc brakes?

most certainly they did. carl fogel posted an excellent example of just
such an event on one of the previous threads.

What about vibration, flex and various other
stresses? Couldn't a QR work loose because of something besides a disc
brake?


Cannondale's test looks a lot like "go away and prove that this is not
a problem" rather than "go away and find out what has to be done to
make this problem happen". As an engineer by training, knowing that
the problem almost certainly has happened at least twice, I would be
inclined to take the later approach. As a corporation with potential
lawsuits to consider, I'd maybe take the first option. No I wouldn't,
but I can see why someone else might.

So, the issue still has not been adequately investigated. And none of
us have the cash to do so. Back to square one.

Guy


Much more important than Cannondale's test is the test that many
thousands of riders do each day. This whole scare is like a ghost story.
Certain people claim to have seen it, but when we go looking for it, we
can't find anything.

Just zis Guy, you know? wrote:
On Mon, 27 Sep 2004 07:01:25 -0700, jim beam
wrote in message :


if the force generate by braking is 1/3 that of
the force necessary to cause slippage [ignoring of course lawyer
lips], then
i can't see what the fuss is about. 1/3 of yield is a well accepted
margin.


But you don't know that it is, because nobody has seriously tested the
proposition (or the possible loosening effect of repeated braking on rough
ground).


who says it's not been tested? just because it's not found it's way
onto r.b.t. doesn't mean that it's not been considered.


You think they'd keep it quiet if they tested it and found no problem?
Remember, the CPSC have not had any submissions on this either. And
the bike trade press are interested, so you'd expect, if nothing else,
a letter from somoene in the trade to one of the trade mags. Instead
we have silence, except for Cannondale who performed a test which
looks to me to be woefully inadequate.


getting back to your point, i've seen no evidence that qr's loosen in
service. they have nylock thread locks and serrated thumbscrews. what
else would be necessary?


Vibration and twisting forces on the wheel causing oscillations in the
skewer tension. Just like any other threaded fastener. See James'
pages for an explanation of the proposed mechanism.

http://www.ne.jp/asahi/julesandjames...se/#unscrewing


as for ejection, if you're worried about it, buy a downhill fork. it's
not like they're no an option!


Really? Where do I get a lightweight downhill fork for an ETRTO 406
wheel? But you miss the point: if the downhill fork is necessary,
then there is a problem!

from what i understand, the big axles on d/h forks are more to do with
preventing fatigue in "standard size" weeny little 9mm axles than
anything else. d/h bikes run 40lbs or more - a substantial increase in
fatigue demand.



personally, i'd be more worried about hydraulic hose failure or brake
levers fatiguing than axle slippage.


I wouldn't, because as long as the bike remains in one piece you have some
options to get off without briefly experiencing unpowered flight.


depends on environment i guess. where i ride, you would indeed
experience unpowered flight, even if the bike was in one piece.


So you think that a front wheel ejecting is no more likely to cause
you to land head first than any other component failure? That's an
odd point of view. It sounds like your riding is far from typical.

i suppose most "mountain bikes" spend more time in urban environs than
on hills, so i guess technically, you're right; my riding /is/ far from
typical. not that i understand why you're still going on about
ejection. from what i've seen, it's /way/ less likely than chain
failure, crank failure, pedal failure, stem failure, bar failure, brake
failure, fork failure, frame failure..................


Guy

jim beam wrote:

not that i understand why you're still going on about
ejection. from what i've seen, it's /way/ less likely than chain
failure, crank failure, pedal failure, stem failure, bar failure, brake
failure, fork failure, frame failure..................

Wheel ejection isn't very likely, granted. Do you really think that
makes it okay?

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/