I desperately need help with this. I have a fixed gear bike I built myself (Ebay wheels, old Schwinn frame, various other parts left over and lying around). I ride it to commute, and have put around 2000 miles on it with very few problems. However, lately my chain has been falling off, and today I couldn't get it to stay on. Had to call my wife to pick me up and then drive into work.

I've tried replacing the crankset/chainring, and cleaning the chain. I suppose the chain could be stretched. Any other suggestions? The chain appears to be straight.

I'm incredibly frustrated right now with this, and am even seriously considering going back to my road bike for commuting purposes. I love riding fixed, but I can't have this much of an interruption of my commute. I'd be grateful for any suggestions people can offer.

R.