Originally Posted by
Bob Dopolina
So this pin wear is where exactly? Where the pin passes through the plates? Do I understand your assumption correctly?
If that is the case then it doesn't matter where the wear is. Any wear will cause an elongation and lateral play in the chain. The elongation and lateral play cause the distance between the center of the rollers to increase and no longer match the teeth on the cassette. That leads to poor shifting performance and eventually slipping under load. If I understand your assertion correctly, flipping the chain over isn't going to solve anything.
Wrong again. In a modern derailer chain, the wear occurs between the pin and the inner side plates, which are shaped to bear against the pin on the inside of the hole and to bear against the roller on the outside of the hole. the roller moves around and wear on it doesn't cause much trouble. Chain "stretch" is really wear between the pin and the inner side plates. That wear is concentrated in a range of about 30 degrees on the pin and the corresponding surface of the plate. That leaves about 330 degrees of unworn surface in even the worst chain. If you turn it over, you can move the load to the clean part of the surface.