コントロールアーム

A control arm, sometimes called an A-arm, is the suspension link that connects the wheel hub and steering knuckle to the chassis. It locates the wheel while letting it move up and down with the road, using bushings at the chassis end and often a ball joint at the wheel end.

The control arm holds the wheel in its correct position while allowing the suspension to travel over bumps. Its bushings let it pivot at the chassis, and its ball joint lets the knuckle move and steer. By locating the wheel accurately through all this movement, it keeps the geometry and alignment correct.

The bushings and any ball joint wear over time, developing play. Signs include clunking or knocking, especially pulling away or over bumps, vibration, wandering steering, and uneven inside-edge tire wear. Because a worn control arm affects alignment and a failed ball joint can cause loss of control, worn parts are inspected and replaced, and an alignment is done afterward.

The correct control arm depends on the vehicle model, the axle and suspension design, and its mounting and ball joint type. Confirm the part against the vehicle specification before fitting.