Wednesday during my commute (rather an errand) I ran over an old rusted piece of a coat hanger. My back wheel hit it and the hanger caught into my chain and went up into my rear derailer bringing me to a violent stop and destroying my rear derailer and cracking my sweet Avenir rack. I was going about 20 mph and the rear wheel just stopped. It was on a highway with fifty five mph heavy traffic. Close call. Back on the sadle today!