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?

Is this the end of QRs for MTBs?

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."


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.


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."


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:


Singletrack forum:


BikeBiz.co.uk bulletin board:


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