Earlier this year Mavic recalled all of its first generation R-Sys front wheels when some wheels failed under certain conditions. The wheels had passed all of Mavic's existing safety tests however the company's engineers devised a new test replicating those conditions in the lab and confirmed that there was a weakness in the original design that could lead to the wheel failing.
In April the French company launched a new beefed up Mk 2 R-Sys which Mavic were certain addressed the problems of the Mk 1 design. All well and good, but this week the faith of many in the R-Sys design took a new blow when Velonews writer Ben Delaney recounted how his new Mk 2 R-Sys front wheel “self destructed”, in the words of a watching bike mechanic, as he took a corner during a race.
So, was this simply the case of a wheel failing in a race, serious for the rider concerned but nothing more sinister, or do the owners of R-Sys front wheels have reason to be worried?
Not yet, and possibly not at all was the response from Mavic yesterday. The man from Mavic HQ was keen to stress that:
“There have been almost no cases of problems with the new wheel [in fact Mavic say this is the only MK2 R-SYS failure they are aware of] if there had been there would have been a recall. We don't play with people's safety, we do all we can to ensure the quality and safety of our wheels, it is too dangerous to play with that, but the unbreakable wheel has not yet been invented”.
Mavic have invested a lot of time, money and credibility in to the R-SYS design in which the spokes are held in both tension (as on a standard wheel) and compression, so the company is unlikely to call time on it without thoroughly investigating every possible cause of a failure. The claimed benefits are a stiffer wheel that benefits from increased vibrtation damping.
Mavic engineers, and investigators from the US Consumer Product Safety Commission (CPSC) are still trying to work out what caused Ben's wheel to fail. Mavic site road conditions, bike speed, rider weight (although the R-SYS doesn't have a weight limit), the condition of the tyre, and the likely forces the wheel was under – in particular the torsional forces at play – as all having parts to play in a wheel failure.
“When carbon breaks it falls apart, unlike steel or aluminium and that can be shocking. The cause is the same, but it has a psychological impact” the Mavic spokesman told us.
The message is that in the wrong circumstances all wheels break, but while carbon wheel might not break any more often than the non-carbon variety (they may even break less) when they break they are more likely to… really break. Although we can't help feeling that a wheel that falls apart is likely to have more than a pychological impact on the person riding it.
And according to our man from Mavic:
“R-Sys have to be considered carbon wheels – you can't treat them like Ksyriums. Carbon wheels do not react in the same way as aluminium or steel, manufacturers need to take that into consideration when they are building their frames, and so do riders. Rigidity transfer [from frame to wheel] has to be considered by manufacturers and also by riders.
“Torsion is a problem and Mavic is working on developing new testing methods to test the effects of torsion on a wheel". Were such tests to find the wheel too torsionally compliant Mavic say they would would beef them up "to balance the frame".
The bracing effect of a a torsionally stiffer frame puts more of that twisting force through the wheel, rather than spreading the load through the rest of the bike.
“Three years ago when the pro peloton first switched to carbon wheels in a big way there were a lot of crashes. We sponsored Vinokourov at the time. He didn't use carbon wheels for training – he didn't like the braking and the stiffness – but like the rest of the peloton as he put more miles in he got used to them: they adapted their riding styles. The same thing happened in Moto GP: as frames became stiffer, riders had to adapt.”
Of course the pros put in thousands of kilometres a year on their bikes, more than enough time and distance to adapt to the demands of new technologies. Where that leaves the rest of us who ride our bikes a fraction of the distance in the demanding environment of a race or sportive – the latter usually involving fast descending over poor roads (if it's in Britain at least) in often treacherous conditions and amongst a crowd of other riders – is another question. Nothing about UK races or Sportives makes for the sort of smooth lines and even braking styles of the pros, and that kind of riding puts a lot of stress on your wheels.
Mavic continues to devise new tests for its wheels to simulate as wide a variety of riding situations as possible – maiming your customers is not the basis of a sustainable business model. As of now the R-SYS Mk2 wheel is not being recalled by Mavic, if that changes road.cc will be the first to tell you. In the meantime we passed on the link posted in our forum of a reported failure of an R-SYS rear wheel – a hitherto trouble-free design that Mavic will now be investigating… We'll keep you posted on that too.
. Golly gosh. Another Bike Fascist. .
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