Locknut

A locknut refers to either a special nut or the positioning of a nut on a bolt that is designed to keep another nut or that bolt from coming loose. Lock nuts are often used in critical applications where serious harm to the user (rider) or damage to the equipment (motorcycle) could occur if the nut or bolt came loose.

On a motorcycle it is not uncommon to find a locknut in use on the front brake lever and clutch lever pivot bolts, tappet adjusters on valves, drive chain adjusters, throttle and clutch cable adjusters.

Locknuts are sometimes called jam nuts.