Saturday, December 20, 2008

Bike Crash Investigation

It's just like Air Crash Investigation, only that it involves a bicycle. And it involves me. There's the dramatic crash, the speculation and theories, then the visit to the scene and some science.

Yes, I experienced a catastrophic failure of my Shimano RS10 bicycle wheel. The front one. That's the one that makes the cyclist lose control instantly.

I should have started noticing the signs:

1. These wheels and its predecessor R550 are notorious for eating up spokes for breakfast
2. There were ominous pinging sounds from the front wheel 2 rides ago. I assumed there were just the spokes bedding into their proper position, since they were new.
3. My average speed had dropped this and last ride. I attributed it to fatigue, but it might have been an untrue rim or faulty wheel hub.

All these signs don't point to any specific mechanistic point of failure, but if I took them seriously, then maybe, just maybe, I would have picked up an early sign of failure of my wheels.

It's one of those 'just riding along' incidents, where nothing was hit, no vehicle, no pothole, no squirrel in the spokes.

The wheel simply exploded, through its own volition. I have piss poor luck these days.

5 spokes pulled out of the rim, the hub was literally floating in thin air as all the spokes rapidly detensioned, and the front wheel had effectively disappeared under me.

I'm still reeling of the shock of surviving a catastrophic front wheel failure with nothing more than 3 spots of road rash and a couple of faint bruises. No sprains, strains or fractures.

But my shifter and rear deraileur have superficial scratches. And my new jersey has a small hole on it.

The cyclist in Trek garb, the taxi driver, the bike shop guys and the bike shop customers were flabbergasted by the severity of the wheel failure. And they realise they're talking to a very obviously ok rider who isn't in any real pain. Must have been a dramatic sight.

It wasn't easy getting a road bike in a taxi boot, and $5.60 to get from one end of Ang Mo Kio to the other is really daylight robbery, what with the falling oil prices and all.

And my bike is out of action for now. Though the frame and fork are okay. No scratches, no bends or cracks.

Thank goodness for the nice and helpful guys at Chapter 2 Cycle. They're getting it replaced under warranty for me. I'm prolly gonna get my bike running again come Monday or Tuesday.

Went home, showered, convinced my parents that I was fully okay, then went out for a jog to the site of the incident. Actually I cheated, I took the bus up the steep uphill stretch. I didn't want to overtrain ad I had not run in weeks.

I retrieved 5 severely bent spokes that my wheel had ejected after the crash, together with my cyclocomputer magnet.

All the spokes that had pulled through the spoke holes were bent. They look like they were compressed from the ends rather than struck by an object in the middle. Unlikely due to a pothole (I checked again - none) or road debris then. Most likely rim failure.

But why? Just take a look at the spoke nipples.

The flanges of the nipples that rested on the rim holes were unreasonably small for a 16-spoke wheel. I compared them to conventional gauge spoke nipples. The latter had a much larger flange, despite the fact that they didn't have to handle as much tension - those are used in wheels with 32 spokes to share the load.

The taper of the flange probably acted as a punch, progressively enlarging the rim hole and subsequently pulling through. These nipples are a new design and are also used on the RS20 wheelset. Shimano's technical drawings show that the previous generation R550 had nipples on the hub end rather than the rim end, with an oversized spoke head on the rim side.

The nagging ache of road rash made me feel grumpy throughout the day.

Looks like I'll have to correspond with Shimano regarding this. Might blow up into a mass recall, if the design of the spoke nipples is indeed unsafe. Not to mention, I want fair compensation for all that had been damaged or hurt by the failed wheel. It had failed under normal riding forces so naturally it's Shimano's fault.

Speaking to acquaintances about what had happened, I'm very disappointed that they're more interested in how I fell and knowing if I was negligent, rather than even wanting to find out how I was.

If you want to know:
I wore a helmet but my head wasn't anywhere near the ground.
I did not hit anything, but the wheel failed anyway.
I wore gloves, but I didn't fall on my palms.
I check my bike before ever ride, but nothing was going to tell me that it was about to fail.
I wasn't riding at unreasonable speeds, I wasn't so foolish as to choose a lightweight wheelset, and most of all, don't talk to me like I had deserved this.

Bloody hell, are these even my friends?

The best advice and support I had gotten comes from the other side of this Earth, over the electrical cables of the Internet: Bike Forums.

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