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05-19-03, 10:44 PM
The following is a string of articles and postings regarding an emerging issue that a friend identified last year regarding fork drop-out and disc brake caliper orientation issues & QR skewers. Please be mindful if you are running front disc brakes in combination with QR skewers, particularly lightweight and/or inexpensive skewers....
----------------------- snip --------------------------
Tuesday 13th May 2003
Is this the end of QRs for MTBs?
A Scottish climate research scientist based in Japan has stirred up a hornet's nest of a safety topic. James Annan claims quick release skewers are no longer 'fit for purpose' on disc-brake equipped bikes. They can and do come undone, says Annan. Riders have so far put this down to their own sloppiness but a recent crash, which left an English rider disabled, has brought the issue into sharp focus. Manufacturers have been dismissive of Annan's emails to date but a growing number of engineering-trained bike experts are lining up behind Annan's theories. Cigarette companies, aware of tobacco-related illnesses since the 1950s onwards, were successfully sued in group actions because of the wilful disregard of evidence that tobacco harms. If the QR problem is ignored, could the bike trade be crippled by similar lawsuits?
After receiving "rude" and "dismissive" replies from global front-fork and skewer manufacturers Annan created a website that lists his shocking theories on the pop-out characteristics of quick-release attached wheels stopped by disc-brakes.
QRs were patented in 1930 by Tullio Campagnolo and - if used correctly - work perfectly well for road bikes and rim-brake MTBs, but they were not designed for use with disc-brakes.
Annan has a whole load of mathematical calculations on his site to back up his theory but here's his summary:
"The crash generally happens when braking hard on a fast descent. To put it simply, the disk pads grab the disk, and push it firmly downwards forcing the hub out of the dropout on the left hand side. As soon as the QR is free on that side, there is no tension on the right hand side either and so it pops out too. The wheel stops moving but the bike and rider continue.
"The forks will be badly smashed in the crash. This has the unfortunate effect of distracting from the real cause. People see the catastrophic failure - broken crown here, snapped stanchions there, perhaps a bent fork blade or sheared fork end. So they see occasional random failures, apparently unconnected and unpredictable. However the snapped fork is a result of the crash, not its cause.
"I suspect that there may be a substantial iceberg effect, with crashes of this type often incorrectly attributed to arbitrary and random factors or just written off as "one of those things". I do not know how common these crashes really are, but it seems to me that they form a substantial proportion of the more serious MTB crashes. They are far worse than a straightforward trip over the handlebars, as when the wheel is lost, the first motion is directly headfirst downwards rather than up in an arc. There is little or no time to react."
Juden
Annan's website might be 'scare-mongering' to some (he believes many 'mystery' crashes, including a recent one that led to an English rider becoming disabled from the neck down, are caused by drop-out failures) but Chris Juden, one of Britain's most experienced bike-and-product testers, is one of many experts who now believe Annan is spot-on.
"It's not just scaremongering, but all hangs together and makes perfect sense," said Juden.
"In fact I'm kicking myself for not thinking of it before."
"Basically, the action of a front disc brake, due to the position of the calliper, is to eject the front axle from the front dropout. The only thing that prevents this is, of course, the clamping of the front axle to the dropout and the 'lawyers lips'. However, the axle-moving force that can be generated by this kind of brake, due to the small diameter of the disc, is hugely greater than anything the customary axle fasteners were originally designed to resist.
"Fasteners subjected to intermittent shear loads tend to unscrew and users of disc brakes have reported forward rotation of their quick-release levers."
Front-facing drop-outs
Brant Richards, a former bike journalist, trained engineer and now owner of On-One bikes is also lining up behind Annan. His latest On-One rigid forks now feature front-facing drop-outs.
He also rides with a set of 20mm axled RAC forks "which make me feel confident."
Annan airs his views on the forum of Singletrackworld.com and many readers of this forum are now paranoid about their QRs coming loose, especially as the rider who was disabled from the neck down was a well-known poster to the Singletrackworld forum. Russ Pinder crashed in mid-March. The exact cause of his crash is not known but Annan believes it could have been due to the problem he believes he's identified.
Warning
Another person worried about the implications of continuing to fit disc-brake equipped MTBs (and tandems) with QRs is Peter Eland, editor of VeloVision magazine and also a trained engineer: MEng ACGI AMIMechE. He's preparing a big piece on the QR topic for his next issue, but he has a warning for the bike trade:
"Assuming the technical side is agreed then manufacturers should certainly be modifying their designs ASAP and warning dealers. As to the existing bikes 'out there' - that's more tricky. Even if every manufacturer recalled every bike ever since disc brakes became common that wouldn't catch all the users at risk, and would cost many parts of the bike biz a lot of money.
"Maybe a better way is education of users about the problem via dealers, the cycling media and presumably also direct mail to manufacturers' customer databases."
Wake-up call
BikeBiz.co.uk has spoken to Annan. He believes the bike trade needs to wake up to the implications of his theory, and quickly.
So far no manufacturers appear to take his ideas seriously.
"Rockshox contacted me [but were] patronising and rude, and I've written to Pace, Hope, Marzocchi, Answer, one or two others [and] Chris Juden of the CTC and a couple of other safety/regulatory bodies such as the US CSPC. Apart from Chris, I've not had anything constructive back. The manufacturers haven't even replied."
Adrian Carter of Pace is aware of the QR issue but isn't convinced Tullio Campagnolo's QR invention can be dismissed just yet. In an open letter, Carter wrote:
"Only a cynic would say that manufacturers would prefer to ignore issues such as these and not offer an opinion. The truth is I suspect that we would all prefer to stay low profile, as in these litigious days offering a view might make them liable (and I would have to say this statement is made without prejudice). However, Pace does not base its designs on unproven principles. Let mathematics and the laws of physics support design and application hypothesis. Subjective views can be dangerous.
"I think it can be accepted that there is no forward moving reaction. To disengage the wheel spindle from the dropout the distance from wheelspindle [centre-line] and brake-pad reaction [centre-line] must increase whilst the force resisting this movement across the disc is the brake pad reaction. Since the disengaging component of this force is less than unity then in our view the spindle will not disengage through brake action alone."
Yet Carter has had his own experiences of wheel pop-outs, only one of which could be attributed to pilot error:
"I have had the experience of a front wheel disengaging and luckily I came away with dented pride rather than a dented face. However over many years of mountain biking I have also experienced a disengaged rear wheel (OK laughs all round)- the calliper was positioned such that there would have been a positive force pushing the spindle back into the dropout. Obviously my fault not tightening the QR correctly - not weird science.
"If we as riders make mistakes such as this, with respect, we should hold our hand up- not try and place the blame elsewhere. Our view is that as long as all products are designed correctly and the rider fits the QR and torques it up correctly the wheel will not disengage."
Faith
Bike expert Jobst Brandt from America, author of the classic book The Bicycle Wheel, supports Annan's theories:
"The more I see on this the more I find the defense of the status quo stranger than fiction. Why are writers trying to say that it can't happen? What motivates writers to claim that disc brakes as currently offered are not a hazard?
"The mechanism has been clearly stated, the forces have been identified in magnitude and direction, and credible descriptions of failures have been presented. What's going on here? There is no Easter Bunny. Believe it!"
Annan's website:
http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.html <http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.html>
Singletrack forum:
http://www.singletrackworld.com/forum/read.php?f=2&i=341361&t=341361 <http://www.singletrackworld.com/forum/read.php?f=2&i=341361&t=341361>
BikeBiz.co.uk bulletin board:
http://www.bikebiz.co.uk/web/bbs2/read.php3?f=1&i=14721&t=14721 <http://www.bikebiz.co.uk/web/bbs2/read.php3?f=1&i=14721&t=14721>
---------------------------------
Friday 16th May
Missy Giove's QR pops open
Pilot error? Hardly. Giove was riding a Skareb fork and XT disks in California on Wednesday. Cycle trainer Dave Smith was with her at the time and had earlier that day read the BikeBiz.co.uk 'QR/disc-brake' story and so was clued-up to the probability it wasn't Giove's fault. In fact, her front QR had been "really tight."
"I was riding with Missy Giove and Rick Sutton [vice president of global sales and marketing for Trixter, see http://www.bikebiz.co.uk/web/article.php?id=2908 ] in some big redwood forest near San Francisco on Wednesday," Smith told BikeBiz.co.uk.
"Missy's QR popped. She had definitely tightened it before the ride as she was doing some goofy stuff.
"The Skareb had the lawyer lips intact. [The] XT skewer [was] really tight. I'd actually mentioned your story to Rick when we were leaving the office."
Giove is planning to publicise her QR popping experience tomorrow at the Big Bear 2003 NORBA National Championship Series, Snow Summit Resort, California.
Monday 19th May 2003
QR/disc brake theory to be referred to Oz standards authorities
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."
http://www.rcta.org.au <http://www.rcta.org.au>
http://www.bikeoz.com <http://www.bikeoz.com>
http://www.johnforester.com/Articles/bicycle_eng.htm <http://www.johnforester.com/Articles/bicycle_eng.htm>
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."
http://www.cpsc.gov <http://www.cpsc.gov>
----------------------- snip --------------------------
Tuesday 13th May 2003
Is this the end of QRs for MTBs?
A Scottish climate research scientist based in Japan has stirred up a hornet's nest of a safety topic. James Annan claims quick release skewers are no longer 'fit for purpose' on disc-brake equipped bikes. They can and do come undone, says Annan. Riders have so far put this down to their own sloppiness but a recent crash, which left an English rider disabled, has brought the issue into sharp focus. Manufacturers have been dismissive of Annan's emails to date but a growing number of engineering-trained bike experts are lining up behind Annan's theories. Cigarette companies, aware of tobacco-related illnesses since the 1950s onwards, were successfully sued in group actions because of the wilful disregard of evidence that tobacco harms. If the QR problem is ignored, could the bike trade be crippled by similar lawsuits?
After receiving "rude" and "dismissive" replies from global front-fork and skewer manufacturers Annan created a website that lists his shocking theories on the pop-out characteristics of quick-release attached wheels stopped by disc-brakes.
QRs were patented in 1930 by Tullio Campagnolo and - if used correctly - work perfectly well for road bikes and rim-brake MTBs, but they were not designed for use with disc-brakes.
Annan has a whole load of mathematical calculations on his site to back up his theory but here's his summary:
"The crash generally happens when braking hard on a fast descent. To put it simply, the disk pads grab the disk, and push it firmly downwards forcing the hub out of the dropout on the left hand side. As soon as the QR is free on that side, there is no tension on the right hand side either and so it pops out too. The wheel stops moving but the bike and rider continue.
"The forks will be badly smashed in the crash. This has the unfortunate effect of distracting from the real cause. People see the catastrophic failure - broken crown here, snapped stanchions there, perhaps a bent fork blade or sheared fork end. So they see occasional random failures, apparently unconnected and unpredictable. However the snapped fork is a result of the crash, not its cause.
"I suspect that there may be a substantial iceberg effect, with crashes of this type often incorrectly attributed to arbitrary and random factors or just written off as "one of those things". I do not know how common these crashes really are, but it seems to me that they form a substantial proportion of the more serious MTB crashes. They are far worse than a straightforward trip over the handlebars, as when the wheel is lost, the first motion is directly headfirst downwards rather than up in an arc. There is little or no time to react."
Juden
Annan's website might be 'scare-mongering' to some (he believes many 'mystery' crashes, including a recent one that led to an English rider becoming disabled from the neck down, are caused by drop-out failures) but Chris Juden, one of Britain's most experienced bike-and-product testers, is one of many experts who now believe Annan is spot-on.
"It's not just scaremongering, but all hangs together and makes perfect sense," said Juden.
"In fact I'm kicking myself for not thinking of it before."
"Basically, the action of a front disc brake, due to the position of the calliper, is to eject the front axle from the front dropout. The only thing that prevents this is, of course, the clamping of the front axle to the dropout and the 'lawyers lips'. However, the axle-moving force that can be generated by this kind of brake, due to the small diameter of the disc, is hugely greater than anything the customary axle fasteners were originally designed to resist.
"Fasteners subjected to intermittent shear loads tend to unscrew and users of disc brakes have reported forward rotation of their quick-release levers."
Front-facing drop-outs
Brant Richards, a former bike journalist, trained engineer and now owner of On-One bikes is also lining up behind Annan. His latest On-One rigid forks now feature front-facing drop-outs.
He also rides with a set of 20mm axled RAC forks "which make me feel confident."
Annan airs his views on the forum of Singletrackworld.com and many readers of this forum are now paranoid about their QRs coming loose, especially as the rider who was disabled from the neck down was a well-known poster to the Singletrackworld forum. Russ Pinder crashed in mid-March. The exact cause of his crash is not known but Annan believes it could have been due to the problem he believes he's identified.
Warning
Another person worried about the implications of continuing to fit disc-brake equipped MTBs (and tandems) with QRs is Peter Eland, editor of VeloVision magazine and also a trained engineer: MEng ACGI AMIMechE. He's preparing a big piece on the QR topic for his next issue, but he has a warning for the bike trade:
"Assuming the technical side is agreed then manufacturers should certainly be modifying their designs ASAP and warning dealers. As to the existing bikes 'out there' - that's more tricky. Even if every manufacturer recalled every bike ever since disc brakes became common that wouldn't catch all the users at risk, and would cost many parts of the bike biz a lot of money.
"Maybe a better way is education of users about the problem via dealers, the cycling media and presumably also direct mail to manufacturers' customer databases."
Wake-up call
BikeBiz.co.uk has spoken to Annan. He believes the bike trade needs to wake up to the implications of his theory, and quickly.
So far no manufacturers appear to take his ideas seriously.
"Rockshox contacted me [but were] patronising and rude, and I've written to Pace, Hope, Marzocchi, Answer, one or two others [and] Chris Juden of the CTC and a couple of other safety/regulatory bodies such as the US CSPC. Apart from Chris, I've not had anything constructive back. The manufacturers haven't even replied."
Adrian Carter of Pace is aware of the QR issue but isn't convinced Tullio Campagnolo's QR invention can be dismissed just yet. In an open letter, Carter wrote:
"Only a cynic would say that manufacturers would prefer to ignore issues such as these and not offer an opinion. The truth is I suspect that we would all prefer to stay low profile, as in these litigious days offering a view might make them liable (and I would have to say this statement is made without prejudice). However, Pace does not base its designs on unproven principles. Let mathematics and the laws of physics support design and application hypothesis. Subjective views can be dangerous.
"I think it can be accepted that there is no forward moving reaction. To disengage the wheel spindle from the dropout the distance from wheelspindle [centre-line] and brake-pad reaction [centre-line] must increase whilst the force resisting this movement across the disc is the brake pad reaction. Since the disengaging component of this force is less than unity then in our view the spindle will not disengage through brake action alone."
Yet Carter has had his own experiences of wheel pop-outs, only one of which could be attributed to pilot error:
"I have had the experience of a front wheel disengaging and luckily I came away with dented pride rather than a dented face. However over many years of mountain biking I have also experienced a disengaged rear wheel (OK laughs all round)- the calliper was positioned such that there would have been a positive force pushing the spindle back into the dropout. Obviously my fault not tightening the QR correctly - not weird science.
"If we as riders make mistakes such as this, with respect, we should hold our hand up- not try and place the blame elsewhere. Our view is that as long as all products are designed correctly and the rider fits the QR and torques it up correctly the wheel will not disengage."
Faith
Bike expert Jobst Brandt from America, author of the classic book The Bicycle Wheel, supports Annan's theories:
"The more I see on this the more I find the defense of the status quo stranger than fiction. Why are writers trying to say that it can't happen? What motivates writers to claim that disc brakes as currently offered are not a hazard?
"The mechanism has been clearly stated, the forces have been identified in magnitude and direction, and credible descriptions of failures have been presented. What's going on here? There is no Easter Bunny. Believe it!"
Annan's website:
http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.html <http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.html>
Singletrack forum:
http://www.singletrackworld.com/forum/read.php?f=2&i=341361&t=341361 <http://www.singletrackworld.com/forum/read.php?f=2&i=341361&t=341361>
BikeBiz.co.uk bulletin board:
http://www.bikebiz.co.uk/web/bbs2/read.php3?f=1&i=14721&t=14721 <http://www.bikebiz.co.uk/web/bbs2/read.php3?f=1&i=14721&t=14721>
---------------------------------
Friday 16th May
Missy Giove's QR pops open
Pilot error? Hardly. Giove was riding a Skareb fork and XT disks in California on Wednesday. Cycle trainer Dave Smith was with her at the time and had earlier that day read the BikeBiz.co.uk 'QR/disc-brake' story and so was clued-up to the probability it wasn't Giove's fault. In fact, her front QR had been "really tight."
"I was riding with Missy Giove and Rick Sutton [vice president of global sales and marketing for Trixter, see http://www.bikebiz.co.uk/web/article.php?id=2908 ] in some big redwood forest near San Francisco on Wednesday," Smith told BikeBiz.co.uk.
"Missy's QR popped. She had definitely tightened it before the ride as she was doing some goofy stuff.
"The Skareb had the lawyer lips intact. [The] XT skewer [was] really tight. I'd actually mentioned your story to Rick when we were leaving the office."
Giove is planning to publicise her QR popping experience tomorrow at the Big Bear 2003 NORBA National Championship Series, Snow Summit Resort, California.
Monday 19th May 2003
QR/disc brake theory to be referred to Oz standards authorities
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."
http://www.rcta.org.au <http://www.rcta.org.au>
http://www.bikeoz.com <http://www.bikeoz.com>
http://www.johnforester.com/Articles/bicycle_eng.htm <http://www.johnforester.com/Articles/bicycle_eng.htm>
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."
http://www.cpsc.gov <http://www.cpsc.gov>