Originally Posted by hhnngg1

I dont' have the answer, but I don't the the right one is to wait until the cords are showing. I had a friend who at one point started getting repeated flats - not pinch flats, and searching his tire, could never fine a shard or pin. Went on for 3 weeks, at which he averaged 2 flats on every 50 mile ride, so he had literally 6-7 flats in a 3 week period. I helped him change one of those and even I couldn't figure out the cause of the flats. His LBS though took one look at the tire (no cords showing) and said that was the culprit. Sure enough, changed it out, and he was back to flat free. (It was a well used tire but the cords weren't quite showing at any point.)