Chain and Chain Drive

The drive chain is the most common way of transferring power from the gearbox to the rear wheel. A chain drive system consists of a small front sprocket on the gearbox output shaft, a larger rear sprocket on the wheel and the roller chain that links them. The ratio between the sprockets sets the final gearing.

Road bikes usually use O-ring, X-ring or similar sealed chains, which keep grease inside the rollers and last much longer. Off-road and small bikes often use lighter non-sealed chains.

A chain needs regular care: clean and lubricate it every few hundred kilometres and after rain, and keep the slack within the range given in the manual. Measure stretch and inspect the sprocket teeth; a worn chain and sprockets should be replaced as a set. Chain and belt drives are lighter and more efficient than shaft drive, but need more maintenance.