Hello List
Jim Merz said: <snip>The 2nd thing that accelerates the failure is riding in the city with lots of stop and go. I used to track stand at traffic lights, then really jump when the light changed. After breaking arms in less than one year I looked at what I was doing to cause this a noticed that I all ways jump on the right side when I take off.
I agree with this as an 'accelerated' cause. (sorry, that's a really bad pun) I weigh only145lbs and have broken several cranks in a few different ways on my commuter bikes. Just a few weeks ago a Ritchey Logic left crank went 'bang' on the 2nd pedal revolution pulling away from a traffic light. When I looked down, there was an open crank radiating outward from the bb spindle, oddly enough through the thickest cross section of the arm, right where the odd bump is. Fortuantly the arm just wobbled on spindle, and I wasn't hurt. The arm looked just fine on a previous cleaning, but I can't say I gave it that close an inspection.
Grant McLean
Toronto, lot's of stop lights, Canada