Thursday, April 23, 2015

Trek recall of 1,000,000 bicycles

Better late than never perhaps, Bikebiz reports that Trek has issued a 1 million bike recall notice relating to QRs loosening and causing crashes. There's still plenty of misdirection and obfuscation, of course. Trek's notice refers to QRs that can open beyond 180 degrees such that the lever gets caught in the disk or wheel. But all their original arguments were that if correctly installed, the QR cannot come loose in the first place. Sadly this is not true, as has been amply shown in practice and supported by the simple theory that I presented a decade ago. That is, under the strong transverse forces that are generated in normal use of disk brakes, the phenomenon of vibration loosening may result in unscrewing of the nut and loosening of the QR. This is elementary engineering that has been known for decades, though poor design and maintenance means that it still crops up occasionally, eg as the cause of this rail crash a few years back.

The last version of my web page discussing this seems to be on the wayback machine here. Perhaps I should get round to hosting it somewhere again. But it's old news, and all I got from it was a load of grief from ignorant numpties who didn't care if others were seriously injured by this shoddy design. Shame it took another case of paralysis before Trek started to take it seriously. Hope there aren't too many more, but at this point it's hard for me to do more than shrug and say "told you so". The QR system is simply inadequate for bicycles equipped with disk brakes. It was never designed to take the forces involved, which are massively greater (and in a different direction) to those generated with conventional rim brakes. Fiddling around with it to try to patch up the problems is no alternative to just implementing a sensible robust design (of which there are several available).


Alocacoce said...

Trek seem to be advising people that the QR will not open by itself if installed correctly.

James Annan said...

Well they would say that wouldn't they.

crf said...

This is a (slightly) similar problem. A jostling key turns the car's ignition switch off, potentially causing an accident. Maybe the biggest point of congruence with the QR issue was the long period of denial of the problem by the manufacturers. Another is that as QR mechanisms where designed in the era before bicycle disk brakes, GM also designed ignition switches in the era before people attached to car keys to loaded-up carabiners.