Sprocket

A sprocket is a toothed wheel that engages the rollers of a drive chain. The small front sprocket sits on the gearbox output shaft, and the large rear sprocket is bolted to the rear wheel hub. The ratio of their tooth counts is the final drive ratio.

Changing tooth counts changes gearing: a smaller front or larger rear sprocket gives quicker acceleration and lower top speed per gear, while the opposite gives longer gearing. One tooth at the front has roughly the effect of three teeth at the rear. Check whether the chain length needs to change.

Worn sprockets have hooked or pointed teeth. Always replace chain and both sprockets together, as a new chain on worn sprockets (or the reverse) wears out fast. Use the correct torque and locking method on the front sprocket nut.