The crack appears to have originated in the most common pedal-rub area of the crank, an area that is abraded by the foot and/or toe strap on every pedal revolution.
I have a few uninstalled campy-pattern cranks in my garage, and this suggests that maybe I should perform a dye-penetrant test (with e.g. food coloring) on my cranks before I bother to mount them on the bike. Other CR members with used and brittle 7075 cranks might want to do likewise.
- Don Gillies
San Diego, CA, USA