Just because I can’t let Adam have the last word on crazy bike breakages.
Here are some photos of the chainrings on my fixed gear after a little mishap going down the hill in Port Jefferson. I was following Matt Lammens, who’s computer maxed out at over 30 mph. About of a third of the way down the hill I was treated to a metal grinding noise and my back tire locked up. Somehow I managed to control the skid for 10-15 feet before my chain popped off. After that it was a simple matter to stop with one brake.
I have no idea what happened. The fact that the outer chainring bent too indicates to me that maybe something hit it.
The moral of this story: When building a fixed-gear bicycle, do not use crappy rivited chainring / crank from the mid 80’s.