Wednesday, March 18, 2009

Wobbly wheels and cracked rims

An interesting episode occurred as part of the PA Spring Forward 200K brevet. After we finished the ride, we stowed our bikes in Jamie's car, one lying on top of the other, with several towels in between. This avoids any direct contact between the bikes. After a 3.5 hour drive Jamie drops me off and I take my bike out of his car along with all the rest of my stuff.

The next day I get a call from Jamie, who is convinced that his wheel is out of true because of the bouncing of the bikes in the car. I am not convinced because:

1) The bikes hardly bounced during our all-interstate drive home.
2) Even if they did bounce, the loads were minimal.
3) It is much more likely for the wheels to get out of true while riding, e.g., if you hit a pothole.

So Jamie takes his wheels to a bike shop only to get a call a few hours later. The mechanic was astonished by the large number of large cracks in his rim. Jamie was probably lucky not to have had a rim failure during the brevet. The lesson to be learned is: inspect your rims once in a while! Below are a couple of pictures of one the amazing cracks.

View I


View II


It is interesting to note that these rims have a wear indicator. Usually these are little indents on the brake track that wear over time. When they are no longer visible that means the wheel should be replaced. I did not inspect Jamie's wheel for these indicators, but given the amount of cracks in the rim, a replacement was due a long time ago.

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