The builder quickly apologises for his error. If it had just been one case, involving a poorly designed custom fork, then that would have been pretty much the end of the matter.
However I remember an earlier thread on singletrackworld.com, in which a rider using disk brakes had been badly hurt after apparently losing his front wheel on a descent. He spent more than a week in hospital with serious head injuries. And back in June, another tandem rider had suffered a failure - this time the skewer snapped, again on a steep descent, with disk brakes.
Although these anecdotes all seem rather distinct, there is still the one factor linking them. They all occurred while descending steep slopes, at a point where disk brakes would be being heavily used. Even excluding my own unusual experience, this failure rate seems a little high especially considering the consequences (I am not aware of a single failure on a rim-braked bike reported by the same groups in this interval, despite the vast majority of riders using them). I start a couple of threads on rec.bicycles.tech and uk.rec.cycling. Everyone is in agreement that the relationship of calliper position and dropout orientation seemed somewhat unwise in general, and positively dangerous on our tandem, but no-one sees how a properly fastened skewer could be pulled out past a retention lip, and skewers don't break all that often. Several of the UK riders have even been using Pace forks where there is no retention lip at all. However some of the contributors mention problems with wheels coming loose, all again linked to disk brakes. I also try on stw, and get the standard replies saying it was all user error, but again a handful report problems. So I remain suspicious - to me, the failure rate (including these near misses) is starting to appear unreasonably high even without an explicit causal description of exactly what is going wrong. Russ Pinder contributes to the u.r.c thread - I only know of him as an occasional poster, who seems to generally know what he is talking about. Like me he is a keen trailquest competitor, but we live in different ends of the country and had never met in competition.
Around this time I also email Hope UK, to ask them about the danger of applying a large force towards the open fork ends. Their reply is to the effect that it is not a problem so long as the fork ends are oriented appropriately. I am intrigued by this and ask them to clarify what that means in practice, given that the vast majority of forks rather obviously have the ends oriented inappropriately, but they don't reply to that. Unfortunately I no longer have those emails.
I am uneasy about the situation, but have nothing more to go on, so I let it drop.
I am now sure that something is going badly wrong with the design, even though I don't know exactly what. This failure rate is unreasonably high, and I cannot believe it is all just a series of nasty coincidences. So I write up my ideas (pointing out the threat due to the ejection force) on my web pages and bring them to the attention of people on uk.rec.cycling and rec.bicycles.tech. I get a pretty sceptical response. As before, people can see the problem if retention lips are not present (as in my own case). Several MTBers mention seeing their wheels slip in the dropout under firm braking, so there is definitely a large applied force, bigger than the friction of their QR can hold. However no-one, myself included, can see how a properly fastened QR can escape past a solid lip. There is also a steady trickle of people who report lucky escapes where they have found their QR loose. Of course everyone agrees that this must be their fault for not doing it up properly. Even so, it seems foolish to arrange the calliper mount so that it forcibly ejects the wheel under these circumstances. At this point I'm almost prepared to argue from an evidential point of view rather than deductive - the failures are happening, so there must be a fault even if I don't know exactly how or what. But I know that won't convince most people.
I also email Chris Juden, Technical Officer of the CTC. He agrees that there is a real potential for trouble when custom builders start adding disk brakes to road (cyclocross/tandem) forks which may have no retention lip, and he says he will try to publicise this fact. Along with the others, however, he can see no real danger on a standard MTB fork with a lip. He is, however, alarmed to hear that some wheel movement is considered commonplace by many riders.
I keep on trying to argue that there is a problem. Maybe the QR stretches and pulls over the lip? I can't even convince myself of that, still less anyone else. But I know there is something going on here. What am I missing? Can experienced adult MTBers really be such a bunch of muppets that they all ride around without doing up the QR properly, or get the coil spring or a bit of mud stuck in the way? If they do, does this mean the QR is intrinsically unsuitable? How could they possibly get this so badly wrong, and why is it almost always disk users who report these problems? Round and round in circles. I don't want to let this drop like I did in December. I am certain that there has to be something going on here - there are too many coincidences.
Eureka! It's a startlingly accurate description of the situation with disk brakes. The brake applies a downwards transverse force (the 'alternating' part may be due either to vibration or simply the upwards ground reaction force when the brake is released). It's already clear from simple calculation that this force is far greater than the QR can be expected to reliably hold by its own friction, and many reports of slippage have already been provided. So then the bolt (QR) unscrews, and eventually the wheel is ejected. Why didn't I think of this before?
I fire off a quick email to Chris Juden, I need to get some real engineers to comment on this. I also post on r.b.t., to see what the resident experts think. Maybe they will knock me back again, but I really think I might have cracked it.
Some of my comments are used to start a new thread
on STW. And now that I'm pointing the finger specifically at skewers
unscrewing, it's amazing how many similar stories are turning up. The
thread attracts well over 100 posts, including many clear descriptions
of unscrewing
and several of wheel losses. Of course some people don't believe it,
but
they don't seem to have any reason other than that they have not seen
it
themselves and cannot believe that the manufacturers might have made
such a big mistake. I'm confident that they will come round once
they've thought about it a bit more. It is immediately clear to me that
it will be hard
for the manufacturers to avoid a massive recall. This is clearly a
widespread
design fault and even if the frequency of failure is quite low, front
wheel
loss has a long legal history. Courts in the USA will never consider it
acceptable
for the system to fail in this way. Maybe they'll be able to make some
sort
of clamp for the fork ends? I email the editors of STW offering to
write
an article, but never get a reply.
I post to the tandem list, and instantly get a
another identikit story about someone's friend riding a solo MTB,
losing the wheel during a long descent, swore blind the QR had been
tight at the start of the day.
An email arrives out of the blue from Russ Rose, director of R&D at SRAM/Rockshox. He offers some patronising 'thanks' about my highlighting the 'importance of correct wheel and skewer installation'. I try to convince him that there might be a real problem but he refuses to take this seriously and breaks off with:
Of course, it's clear that the case for disk-induced QR loosening has never been argued in court, since no-one had thought about it before.
I try again on rbt
and urc, challenging people to tell me why I'm wrong. This time I
get a couple of bites and Jobst Brant agrees with me. It's good news to
have more explicit support from respected names.
Members of the MTB tandem list seem to understand
the
issue straight away, and a few of them help by spreading the story
around
and generally sticking up for me in far-flung web-sites.
Pace issues an Open Letter which is posted
on stw. I copy it to usenet. Several posters are relieved that Pace
have 'proved' that there is no problem after all, but others spot their
mistakes. I'm surprised they can't put up a better defence, and amused
that
Adrian Carter has himself lost a front wheel but still cannot see the
problem.
I'm not too impressed with his insinuations about my 'weird science',
which he does not back up with any argument or evidence. I provide my
own
reply, posted and emailed (Pace make no further public comment and do
not
reply to the email). Another lengthy
debate ensues on STW. It seems to me that some people are now more
determined to prove me wrong rather than take an objective look at the
problem, and I'm getting accused of scaremongering and organising a
witch-hunt. I can see that I'm getting increasingly shrill, but what do
they want me to
do, just forget the whole thing? The manufacturers are still refusing
to
take the issue seriously. Apart from Pace, they haven't even
acknowledged the potential for concern, still less provided any
rebuttal of my case.
I email various manufacturers, but never get a reply. Also email Ernst Brust of velotech.de, a German testing lab that is supposed to be interested in these things. But I don't speak German, and don't hear back.
Bikebiz starts to run a series of hard-hitting articles, some of which are copied elsewhere. The second article contains a comment from Trek's lawyer, Bob Burns, which is very interesting. Firstly, he says that they have never heard of any such problem, but then he appears to contradict himself by going on to explain how they have always shown this supposedly nonexistent wheel loss to be the user's fault:
The analysis of a loose QR immediately prior to the
crash is correct, but seems clear to me that the conclusion of operator
error is not justified, since even a correctly installed QR may work
loose due to the applied forces. No-one else seems to pick up on these
comments.
I email John Forester and he replies with the 'gross
negligence' comment. Obviously he didn't use those words by
accident, and Carlton copies them into another Bikebiz article.
What exactly does 'pop open' mean in "Missy
Giove's QR pops open", and what actually happened?
If the 'possibility of a problem' really is
small, then it's yet another big coincidence that it happened right
away with the one and only set of components that he tested. Anyway, at
least now after
3 months of insisting that my ideas are all rubbish, he has seen the
proof
with his own eyes, so he can at last stop trying to prove me wrong. His
opinion
convinces some more people on STW, so I'm not going to complain too
much.
The Bikebiz article mentions earlier off-the-record
advice from a Trading Standards officer to a bike shop to stop selling
disk forks, but this is not mentioned in the STW version, which instead
adds some 'perspective' from the editor about how it's not really worth
getting worried about.
A particularly bad injury reported to me via email,
the rider is still in hospital with serious head injuries. My
correspondent (a relative) seems very angry that no-one has done
anything about this problem yet, and I expect to hear more about this.
Two more failures mentioned on
STW,
the usual suspects are desperate to find an alternative explanation for
the front wheel losses but of course both riders were using disks. Another
injury mentioned 2 days previously was only reported due to a
chance encounter on a ferry. I'm amused to note on that thread
how the
attitude of the typical poster to risk with respect to helmet
(non-)wearing
contrasts with the attitude that has been displayed towards the risk of
front wheel loss - it's scaremongering of me to suggest that the latter
is a concern, but anyone who doesn't wear a helmet is a moron because
they could potentially fall off and hit their head.
A few days later I hear a vague description of
another incident, this time it's a rider I know personally (a little).
Interesting that this also does not get mentioned on STW, this rider is
surely well-known and the crash occurred during an organised event.
That makes 5 in a week, the worst cluster by some way. I wonder if I'm
hearing of most UK incidents, or only the tip of the iceberg.
Chris Juden's article entitled 'Disk danger'
is in the CTC magazine:
I hear that Cannondale might be putting Avid disks
on their
road tandem next year. That's doubly odd as Avid keep on insisting that
their
disks are not suitable for tandem use, although plenty of people use
them
successfully.
I prod the CPSC and they promise to write soon.
From the tone of the email I can guess what's coming, and sure enough
when the letter arrives (unofficial copy by
email) it says they are not going to do anything. They are instead
passing the buck to the ASTM which is an industry body, the chairman of
the relevant committee is from Answer/Manitou and he has already stated
in a previous Bikebiz
article that he doesn't believe there is a problem. Some people seem to
think that the CPSC's (lack of) response is shirking their
responsibility,
but what about those who shirked their responsibility to tell the CPSC
about
their experiences of the problems a couple of months ago? Ben Cooper
has
a different
view:
Of course he knows for sure there is a real problem
since he has reproduced it himself, but it still seems to me like he is
the
one scaremongering now. I almost have sympathy for the CPSC, they are
looking rather impotent but if no-one is prepared to refer any failures
to them then they probably have little alternative but to accept the
word
of the manufacturers that this problem does not exist.
The ASTM committee meeting is in October, and
I
can't believe they will do anything useful without a massive kick up
the
arse. Does there really have to be an expensive legal battle before
this
problem gets fixed? It's really starting to look that really might be
the
case. 5 months ago, I never thought that it was going to turn into a
classic
case of corporate denial and cover-up. The problem now seems so trivial
to
understand and demonstrate that I do not see how they can possibly hide
from
it. Then again they have managed to pull the wool over the CPSC's eyes.
Mark@singletrack, Ben Cooper and several others seem
to have now decided that I am the only remaining problem, and that now
the
real players are supposedly looking into it, I'm doing more harm than
good with my 'campaigning'. I only wish I could believe them. It would
certainly get fixed quicker if more people were prepared to do
something
other than sit on the sidelines and criticise. Do they really think
that
waiting until 2005 for a solution is going to work?
Erickson now seem to be putting their disk mounts on
the front of the RH fork blade of their tandems, but no-one else has
taken such a simple step. Indications for next year's forks and MTBs
from most manufacturers
seems to be that there will be more disks on lower-priced bicycles,
although
perhaps bolt-through forks are also growing in popularity.
I get an email from a shop owner in the USA who is
seriously worried about his liability. He has seen the skewer loosening
problem
with his own eyes while setting up and testing bikes for his customers.
He is considering dropping disk brake forks from his product range, but
obviously that's a difficult step for a small business to make. There's
not much I can say to help him, IMO he's right to be worried, and the
manufacturers are behaving very unreasonably in leaving people like him
hanging out to dry. I support his aim of asking hard questions of the
manufacturers and wonder how many more there might be who are prepared
to stick their necks out like he has
I also hear a rumour that Pace are going to put some
sort of retention on their forks next year. I hope they are going to do
something effective. Would be ironic if they adopt lawyer lips just as
the rest of the world realises how inadequate they are - although even
these would surely reduce the hazard, as Pace forks feature highly in
my catalogue of wheel losses. Reviewing the list of failures I have
heard about, it seems that this might be a factor that explains why the
problem seems less common in the USA compared to the UK. However the
problem is certainly not confined to Pace forks even if they do present
a greater danger than most others.
