I've been running 52X19 since I set up my Peugeot over a year ago. Today I was riding just south of Dupont Circle in DC, I was going over some bumps, and my cog broke. This of course caused the wheel to lock up as the chain wrapped around it. It sent me into a pretty awesome skid, but I maintained balance.


Here is the piece that broke off

While I've had the set up for a long time, I've been out of the country of 8 months, and thus the cog has pretty little wear. My chain tension was good... What could have caused this?

btw, I had noticed some slight warping in the chain-ring, it's the original peugeot, and kinda wimpy... could the slight side to side motion of the chain have caused the cog to fracture?