Control Arm
A hinged suspension link that connects the vehicle frame to the wheel hub assembly, allowing the wheel to move vertically.
A control arm (also known as an A-arm or wishbone) is a key component of a vehicle's suspension system. It acts as a hinged link connecting the vehicle's structural frame or subframe to the steering knuckle or wheel hub assembly. Control arms allow the wheels to move up and down over bumps while keeping them securely positioned relative to the vehicle.
Most control arms are triangular and feature rubber or polyurethane control arm bushings at the frame attachment points, which damp road vibrations. The outer point attaches to the steering knuckle via a ball joint, allowing for pivotal movement during steering and suspension travel.
Control arm assemblies wear out over time. The rubber bushings can dry rot, crack, or tear, leading to metal-on-metal contact. The ball joints can also develop play or lose their lubricating grease. Symptoms of worn control arms include clunking or squeaking noises over bumps, steering wheel vibration, loose or wander-prone steering, and uneven tire wear.
Replacing a control arm involves removing the assembly and installing a new unit containing pre-installed bushings and a ball joint. Because it affects the wheel suspension geometry, a wheel alignment is necessary after control arm replacement.