Wednesday, September 09, 2009

Broke Another Wheel

A few months ago, I tacoed the front wheel of my commuter. Last Sunday, I broke two spokes in the rear wheel. I was on my way to work and since I had several pounds of hand tools in a bag in one of my baskets, I decided to take a flatter route to work, via a multi-use path along Westlake Avenue. There's a point along that route where the paved trail shifts to the right. It was pretty early, since I had to be at work at 8am, and it was pretty cloudy and a little rainy. I saw that the pavement went off to the side, but I was going at a pretty good clip and it looked like going straight ahead just put me onto a gravel surface for several yards, which then rejoined the trail.

It turned out to be an old section of railroad track, with ties still present. I managed not to wipe out when I hit the first one, pretty hard, then I slowed down slowly, which felt like riding a jackhammer, and walked to the end of the section. I noticed that my handlebars were tipped way down, which I corrected, and then I resumed my ride. When I got to work, I noticed that one of the spokes was going to the hub out of line with the spoke head. I was running later than I'd have liked, so I left the bike in the stands (I was working at Safeco Field) and joined my crew.

At the end of the day, I took some time to figure out how many spokes were broken - two, on the non-drive side - and wrap them around neighboring spokes. According to cycle tourists, that's the best temporary solution because while I probably had the tool to unscrew the spoke from the nipple, that allows the nipple to fall into the wheel and rattle around; keeping the spoke keeps things closer to their proper order. I stopped at REI on the way home since it was too late to go to a bike shop. I don't understand why bike shops don't keep retail hours. Bought a couple of new spokes, went home, couldn't install them. The freewheel and pie plate were in the way and I'd have had to bend the spokes significantly to get them around them.

Can you spot what's missing? One of them's right above the reflector and the other is almost exactly opposite it. Since spokes work under tension, when a wheel is hit with a significant force, the rim wants to go from circular to elliptical. The spokes under the most tension are the ones the hub hangs from, and those running closest to the major axis of the ellipse formed by the rim under deformation. So it's something of a no-brainer that the two that I lost were along that axis and on the non-drive side, which is frequently more problematic on a dished wheel.

Lots of negative space when the rear wheel is missing. Also, a bike that can't take me to work. I took the rear wheel to the shop sponsoring my team and borrowed a freewheel remover to get it off. Then I laced the two new spokes into the wheel and trued it on their stand. The wheel had some pretty incredible wobbles in it, and the spoke tensions are all over the map now.

I'm not sure how much longer this wheel's going to last, and it's going to be a pain to replace it. It's a 27" wheel with a six-speed freewheel, so probably 126mm dropout spacing. I'm somewhat committed to using a 27" rim and a 126mm OLD threaded road hub. If I changed the rim size, I'd also have to change the rear brake and get a new tire, and while neither of these is particularly difficult, it adds to the expense. I can't use a differently sized hub in this bike since the frame uses a bonded aluminum construction and might respond poorly to respacing. I also don't want to change number of speeds since I'd have to replace my shifter, which is a fairly expensive upgrade even on a bike this old. I also want to stick with Shimano shifter, derailleur and freewheel, or at least Shimano-compatible, because I like it that the indexing works. The hub's also toast, but a new rim and spokes would cost more than a cheap rear wheel.

Luckily, enough people are trying to keep beater bikes like this rolling as working bikes, not just project and restoration bikes, that there are some cheap rear wheels out there if I need one.

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