Front & rear sprockets (chain kit)

How it works

On a chain-drive bike, the final drive has three parts that wear together: the gearbox output sprocket (small, at the front), the rear sprocket fixed to the wheel, and the chain linking them. The ratio between their tooth counts sets the final gearing. With mileage, the teeth wear into hooks or points and the chain stretches. Because a worn part wears the others, all three are replaced together as a chain kit. A worn kit shows hooked teeth, a chain you can pull away from the back of the rear sprocket, tight spots, or a chain that constantly needs re-tensioning. A poorly maintained drive snatches, gets noisy and can break, which is dangerous. A clean, lubricated, correctly tensioned chain makes the kit last much longer. When fitting, wheel alignment and chain tension are set as the manual describes.

Maintenance tips

• ✓Check wear: if you can pull the chain away from the back of the rear sprocket far enough to see part of a tooth, the kit is worn.
• ✓Always replace chain and both sprockets together.
• ✓Lubricate the chain and check its tension regularly, and after riding in the rain.
• ✓When fitting, check wheel alignment with the adjuster marks and torque the wheel spindle.
• ✓Rivet a new chain with a proper tool; a badly fitted clip link can come off.