In automotive suspension, a control arm, also known as an A-arm, is a hinged suspension link between the chassis and the suspension upright or hub that carries the wheel. Control arms control the motion of the wheels so they’re in line with the car’s body. They are typically equipped with bushings on the frame side of the vehicle and a ball joint on the wheel side of the vehicle that allow flex and controlled movement according to road conditions and steering input from the driver.
Control arm bushings are important for driving comfort and handling. They cushion the suspension system which in turn controls noise and vibrations, and also provide a softer ride over bumps. Control arms are most commonly encountered as part of the MacPherson strut independent front suspension. The control arms are perpendicular to the axis of the vehicle and are termed track control arms.