How Chains Wear

Different types of chains

Motorcycles and bicycles both use what is called a 'bushing' chain. Bicycles over five speeds must use a 'bushingless' chain, due to the great angular displacement between cogs. Motorcycles tend to add o-rings within the chain parts for keeping dirt out and lube in the inner workings of the chain.

The 'Stretch' Myth

Chains do not stretch, they wear. Strech of the materials in the chain is impossible given the relatively small forces that a motorcycle or bicycle can generate. The wear takes place where the pin from one link meets the bushing (or plates) of the next link. Interestingly, Since on every other link two pins are shared by one outer plate, The chain changes length only between every other link.

Rohlhoff - Theoretical initial schematic

Rohlhoff - Worn schematic

Measuring Chain Elongation

To measure chain elongation, measure as many pins as you can in a straight line and off the sprockets while gently applying a load to the chain. Devide the length you get by ((the number of pin measured - 1) * Theoretical pitch of the chain))

Bicycle Chain Limits

Replace a bicycle chain after it has elongated 0.5 %.