Jockey Wheel (Chain Roller)

A jockey wheel is a small idler wheel that presses against a chain or belt to keep it at the right tension or guide it along its path. Inside many engines, cam chains use similar tensioner and guide rollers.

On off-road motorcycles, chain rollers mounted on the frame or swingarm stop the drive chain from rubbing the swingarm or slapping around as the suspension moves. They are wear parts: the rubber or plastic surface wears through, and bearings seize after exposure to mud and water.

Check the rollers when you clean and adjust the chain. A flat-spotted, cracked or seized roller should be replaced quickly, as it will wear the chain and swingarm. Similar rollers are fitted to many ATV and scooter drives.