I got a rear one cheap because the shop guy had split a pair for a customer and wanted to get rid of it. Because they are fast-wearing, I put it on the front to try it out, and I couldn't believe how crap it was!! I also thought mine was flat. I dunno how 'bad' it is to have the rear on the front, but it even effected the handling of my bike -- it wouldn't steer/track properly. It was like having a garden hose on my wheel!