I tried hopping over a traffic cone once. Must've been bored or something. Anyway, the front-tyre cleared the cone OK, but I wasn't going fast enough and came down on top of it with the back wheel. Squeezed teh soft rubbery thing between my rear-wheel and chainstay and ate it. Jammed my thumb into the ground and figured I sprained it. When it turned black & blue a couple days later, I went to the Health Center on campus and they said I broke it. Fortunately it was all set correctly so they didn't have to make any cracking adjustments. Gave me a splint for a couple weeks and I stay clear of cones now...