That's a fact. My wife had a Fiat Seicento car and at 48000 miles it developed an oil leak at the crankshaft pulley. The dealer had to replace the seal AND the pulley. There was a neat groove worn into the pulley all the way round where the lip of the seal had worn it out. The dealer said this was fairly common.They are made of a special tough steel alloy that alows them to be flexible without breaking and they have a hard machine chrome finish that is ground to final size. The chrome finishprotects the steel underneath and makes for a hard surface for the rubber seal to ride on. Suprisingly, rubber will wear steel down unless it's one of the harder steel alloys.