Joined: Jun 2011
Posts: 1,180
Likes: 0
From: Sunnyvale, California
Bikes: Bridgestone RB-1, 600, T700, MB-6 w/ Dirt Drops, MB-Zip, Bianchi Limited, Nashbar Hounder
1. Check the crank set. Are the chain ring bolts on tight? Check for less likely failures too, like cracks in the crank arms.
2. Check the BB. Is the BB loose? Are the fixing bolts that attach crank to BB spindle on tight?
3. check the frame at right chain stay near the bottom bracket. Have someone stand on left pedal with brakes applied and see if you see a micro-fracture in the chainstay or area close to the BB.