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Failed Shimano Dura-Ace Right Crank

From http://www.flickr.com/photos/50263543@N00/3196400712 as of 2012/09.

Rider was accelerating from a light when there was a "snap" sound and the rider's foot was askew, although the did not break off entirely. Rider was not injured.

Service history unknown; a note a http://www.flickr.com/photos/cmphoto/154412471/in/set-72057594097491531 says "crankset from a co-worker".

It appears there is some darkening on the outermost face, but that may be a phography artifact. The outer face is rounded, similar to FAIL-026, FAIL-029, FAIL-090, the Shimano Deore crank at FAIL-168, and FAIL-169. See FAIL-169 for why a rectangular crank section might have given better service here.

Compare to the wear patterns on this unrelated crank ridden by a different rider. The surface is scuffed from shoe wear, and this may lead to significant stress risers. For this other crank, the wear is well away from the failure point on the first crank. It is not clear whether surface wear played any role in the failure.