My bike has developed a knock or tap with every turn of the pedals. Taking into the shop tomorrow. I'm thinking it's the bb bearings, and if it is this will be the second one I wore out. FSA Mega EXO crank with the external bearings. I seem to get about 4 years, 12k, on them. Does that sound about right for it? My old Scwhinn Superior was 30 years old before I serviced the bb for the first time. That was a nice bike, sorry I sold it.