Sin-gineering (an FMEA exercise)

By now, every self-respecting cyclist on earth has heard this account of a Mavic R-Sys wheel exploding spectacularly under a VeloNews reporter. Needless to say it's not very good press for our snooty friends across the pond.

If you compulsively scour online bike news to the the first one with every tidbit of new gossip, you may have also already read Mavic's strained response where they attempt, with a questionable level of convincingness, to make the point that the wheel's failure was a result of the crash, as opposed to cause thereof. Even if you did fleetingly entertain the belief that this were the case, it still doesn't absolve Mavic engineers of being cognitively disabled (notice how PC I am today?)

Those of you who are engineers probably recognize the Acronym FMEA--Failure Mode and Effects Analysis. Simply put, FMEA is an exercise that one performs with a product or system to identify the many ways that the product can fail and assess the potential risks posed by each mode of failure, the point being that one must expect that some products will fail and that an acceptable failure mode is equally important a design criteria as the performance characteristics of the product when intact.

Generally, when performing FMEA one identifies the failure mode, (catastrophic atomization of wheel resulting in high-velocity faceplant), the severity (high-velocity faceplant seems pretty severe...) and the frequency of occurrence (I can't imagine they made more than 10,000 of these things, so even one failure is a pretty big deal).

If you're an engineer, your job is to make sure the stuff that will get you sued basically never happens. For instance, you should be pretty darn sure that if you're a wheel maker, your wheels don't blow up if you breathe on them wrong. It may be true that being breathed on is not in the description of the wheel's normal use, but it's darn likely, given that they cost $1,200 and are designed like the wheels on an 18th century pushcart, that someone sooner or later is going to lean in real close to get a good look, and since they likely haven't ridden the wheels yet, they'll still be breathing.

It is for the reason above that the engineering world invented "Factors of safety". If you know that a certain component failure--say the lift cable on an elevator snapping--is going to hurt a whole bunch of people really badly (hopefully you're making the analogy here all by yourself), then you build that component a whole lot stronger--say 11x (which is actually the factor of safety for elevator cables)--than you ever expect it to be strained. When was the last time you heard of an elevator cable snapping, despite there being thousands of elevators in every major city, many of which are shoddily maintained and decades old? Yep, never. It simply doesn't happen.

Anyone who's been riding bikes for a long time knows that awful things happen to wheels. You hit potholes. You graze other cyclists or bushes on the side of the road. Occasionally you slide out or have to jump over something. Rims get bashed. Spokes break. Normal wheels, even the ridiculously expensive deep-dish carbon tubulars, weather these sorts of things every day without exploding and tossing anyone, but if any of the above happened to an R-Sys wheel Mavic would throw up it's hands and say, "not the intended use?" Sorry sir, you're not allowed to ride this wheel in the real world, it's simply too dangerous...

The fact that the road-cycling world would even accept a product so ridiculous in the first place, nevermind allow any attempt to defend it, is another example that there's something seriously amiss in roadie culture. A MTB product that performed like the R-Sys wouldn't last a day. Clearly playing in the dirt keeps some of us grounded.

Ride stuff that works. It could save your life.