QR/disc brake theory to be referred to Oz standards authorities

Discussion in 'Cycling Equipment' started by James Annan, May 19, 2003.

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  1. James Annan

    James Annan Guest

    The latest article from bikebiz.

    The question has to be asked, why has this story not yet appeared on any USA cycling news web sites?
    Scepticism is one thing, but not reporting it at all seems remiss. They can't all pretend to not
    have noticed it.

    Noting that Missy Giove was reported as using an XT skewer (and two more people have also
    specifically mentioned them in failures) I think Chris Juden's comments are a little overconfident,
    although there is little doubt that a good skewer will reduce the frequency of failure compared to
    some of the feebler models. Of course it's strictly true that nothing nasty is 'likely' to happen,
    but that's not a very helpful standard to adopt in this case.

    Monday 19th May 2003

    After reading the articles about the QR/disc brake issue on BikeBiz.co.uk, the executive officer of
    Retail Cycle Traders Australia Inc, the Oz equivalent of the ACT, is to raise the matter with
    Standards Australia and the Australian Competition and Consumer Commission. Could the US CPSC be far
    behind? Possibly not as more US bike experts are lining up behind the supposed "scare-mongering" of
    James Annan. John Forester believes manufacturers could be guilty of "gross negligence".

    The RCTA's Graham Bradshaw said:

    "I have flagged [the issue] to Bicycling Trade Magazine [of Australia], and a couple of others, so
    there are others out there helping raise [your story's] profile.

    "I will be commenting on the subject in the members' newsletter later this month, and will also be
    raising it with Standards Australia, and the Australian Competition and Consumer Commission, who
    administer the mandatory standard for bicycles here."

    James Annan said he had emailed the CPSC, the US safety body that can trigger product recalls,
    regarding his theory but had yet to get a response. Even relatively minor defects can result in
    costly recalls. Of course, the CPSC would have a tough job launching a general recall of all
    disc-brake equipped bicycles because that would involve too many bikes without Annan's "defects."

    Bridgestone In a case that could prove to provide some parallels, Bridgestone Tyres of the US
    voluntarily recalled 6.5 million tyres in August 2000.

    According to Bridgestone, this was done "out of a commitment to public safety and consumer
    confidence, Bridgestone/Firestone has decided to recall the tires even though no definitive cause
    has been determined. The number of incidents reported has been relatively low in proportion to the
    vast number of tires on the road and miles driven."

    QR tips Back here in the UK, CTC technical officer Chris Juden said:

    "I'm expecting that the main problem will be found to be poorly-designed after-market fasteners, but
    that designs of forks will nevertheless change. In the meantime I don't think anything nasty is
    likely if you have fasteners with radial steel serrations (like Shimano quick-releases or track
    nuts) and fasten them properly into forks with 'lawyers lips'. And that probably covers most
    disc-braked bikes, as originally sold."

    Failure nodes US writer John Forester, author of 'Effective Bicycling' and an expert witness in
    cycle-related court cases, believes the way wheels on some disc-brake equipped bikes continue to be
    attached by QRs is nothing short of "gross negligence."

    "Any brake designer needs to know how the torque developed by the brake is transmitted to the frame
    of the bicycle.

    "It is immediately obvious that with the caliper pads at the rear of the brake disk the torque
    developed by the brake is transmitted by a couple that consists of upward on the brake frame to the
    fork, and downward through the axle, again to the front fork. The near vertical slots in the
    conventional front fork are to permit the front wheel to be removed by downward motion, and are
    quite secure against the normal weight of the cyclist bearing down on them.

    "But they are not designed to resist significant downward pull. The problem is not with the axle
    fastening system, but with the design of the brake. The brake pads should have been located so that
    the torque couple is transmitted, say, by forwards and backwards forces on the front fork, or even
    by an upward force on the axle assembly and a downward force resisted by some form of rigid fixing
    to the front fork."

    On his website, Forester has an article entitled Some Examples of Failures in Bicycle Engineering
    that have Caused Accidents. He doesn't yet refer to the QR/disc brake problem but what he says could
    prove to be pertinent:

    "In most cases the cause [of a cycling accident], whether it is easy or difficult to discover, is
    not a failure of engineering design, but of conditions that exceed the capabilities that have been
    designed into the bicycle or the facility, or of the operator.

    "Bicycles are not expected to survive undamaged when being ridden against curbs, curves have a
    maximum safe speed, human beings cannot make decisions instantly. Engineering knowledge enables us
    to provide reasonable explanations for many accidents.

    "However, there are other accidents that are caused by engineering error. As the eminent Professor
    Henry Petroski has wisely observed, "I believe that the concept of failure ... is central to
    understanding engineering, for engineering design has as its first and foremost objective the
    obviation of failure. ... To understand what engineering is and what engineers do is to understand
    how failures can happen and how they can contribute more than successes to advance technology."
    Every advance in engineering brings with it new failure patterns that must be understood before we
    can guard against them. I have investigated quite a few accidents in which the cause stemmed from
    the failure of new ideas whose failure modes were not properly understood by the initial designers."




    The U.S. Consumer Product Safety Commission The CPSC is "charged with protecting the public from
    unreasonable risks of serious injury or death from more than 15,000 types of consumer products
    under the agency's jurisdiction. Deaths, injuries and property damage from consumer product
    incidents cost the nation more than $700 billion annually. The CPSC is committed to protecting
    consumers and families from products that pose a fire, electrical, chemical, or mechanical hazard
    or can injure children. The CPSC's work to ensure the safety of consumer products - such as toys,
    cribs, power tools, cigarette lighters, and household chemicals - contributed significantly to the
    30 percent decline in the rate of deaths and injuries associated with consumer products over the
    past 30 years."


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