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Sunday, April 12, 2009

The lifetime of bike parts

I broke another set of industry standard SKS mudguards yesterday, marking the second pair of SKS mudguards I've destroyed in 5 years. I'm generally sanguine about parts failing, since they do face a harsh environment, but I guess I have a few months before the next rainy season before I start thinking about getting Honjo fenders.

Over the years, I've collected through personal experience various expected life time for parts, so I'll summarize them here in order (from most frequently replaced to least frequently replaced):
  • Chains. These don't last more than about 2000 miles if you ride every day and don't keep them squeaky clean. If you keep them clean, you might get about 5000 miles out of them. The longest lasting chains are single speed chains on fully enclosed crank case bikes --- those will go about 10000 miles between replacements.

  • Tires. Depending on how heavy you are, these can range from 1000 miles (28mm tires on my tandem) to 4000 miles (23mm tires back when I was running Michelin Hilite Comps). You can double their lifetime by starting new tires on the front and then rotating them to the back when the back is worn. (That's the recommended replacement procedure!)

  • Bar-tape. These usually die every year or so.

  • Deraileur cables. These don't last much more than 2 years or about 8000 miles. The inner wire usually frays from the end if you don't cap them, or snap in the shifter if you have bar-ends or STIs. Downtube shifters will give them longer life. By contrast, deraileur housing lasts almost forever. I've only replaced one due to rupture in about 15 years of active cycling.

  • Brake pads. These are entirely dependent on weather conditions. On fair-weather bikes, you can run the same pads in California for a decade or more! For commute bikes, I replace them every 4 years or so, but if I was living in Germany or Seattle, I'd have to replace them every year. Heck, mountain biking in Seattle, I had to replace the brake pads every other ride!
  • Chainrings. These last about 15000 miles in optimum conditions (tandem timing rings, which don't have any cross-chaining during their life), or 10000 miles in on a normal bike.

  • Bottom bracket. Phil Wood sealed BBs are supposedly good for about 20000 miles. I once rode one for 40000 miles, but apparently you couldn't turn the spindle by hand after that if you removed the cranks. After last year's stint in Germany and France, though, I ended up with a BB that wasn't smooth after only 8000 miles. So much for 20000 miles...

  • Cassettes. These go every 30,000 miles or so. If you don't replace your chain often, you can expect them to go earlier. The strange thing is that if you do replace your chain often, the failure mode isn't that they wear down --- the failure mode is that you break teeth in the sprockets! Very weird.

  • Brooks saddles. On my singles, these have gone as much as 12 years. But on the tandem, they don't last more than about 5 years or so. That's because you don't stand up enough on a tandem so the leather gets soaked every hot ride.

  • Seat posts. To be honest, I've never had to replace one in 15 years of riding, except for the carbon seatpost after only 3 years, which has scared me off carbon seatposts for a long time.

  • Cantilever brakes. These have proven extremely unreliable for me. I've gone through 3 sets on about 8 years of active mountain biking, and they fall apart in weird ways, most of it having to do with the springs inside popping out. I don't think they should be spec'd on bikes.

  • Deraileurs. The front ones don't seem to be good for more than about 5 years or so --- at least, until recently, that's how frequently I've been replacing them. Recent stuff seems to be getting better, so now I don't know. Rear deraileurs are good for about 60000 miles, with a pulley replacement every 20000 miles or so. I used to be able to say that I've never worn one out, until I sold a bike to Lea that she claimed had a worn out deraileur. In my defense, I never noticed a problem when I was riding the bike, but then I wasn't running 10-speed either, which has much closer tolerances than the 7 or 8-speed stuff I was running. According to an old-timer in my bike club, you used to have to replace rear deraileurs every 20,000 miles or so, until Shimano came along and started actually engineering the part!

  • Cranks. Now we're getting into stuff I've never broken. My 17 year old bike still has a good crank. Now if you're big and strong you might expect to break one every 10 years or so, but the real answer is if you're that big and strong you should be examining your bike every year with an eye to seeing cracks in frames and stuff.

  • Frames. For me at least, these don't go bad unless you get run-over by a car (and unfortunately, that's happened).

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