The Anatomy of a Control Arm

June 3, 2021
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The Anatomy of a Control Arm

ound on virtually all road-going suspension systems, control arms are located at the front axle at each of the two front wheels. They are comprised of either stamped steel, cast iron, or cast aluminum as their primary material. Steel and iron control arms deliver strength, sturdiness, and the ability to resist damage. Cast aluminum control arms are intended for lighter weight applications.


Control arms are typically A-shaped, L-shaped, or wishbone-shaped, but designs differ from vehicle-to-vehicle based on suspension geometry. These components have connection points at each end for attaching a wheel's steering knuckle to the vehicle frame.


At the frame or body, the control arm connects to a hinge by bolts and bushings. These bushings guard against metal-on-metal contact when the arm is moving up and down with the wheels. The bushings also reduce overall noise, vibration, and harshness (NVH) while making the vehicle's ride quality softer and more comfortable.


At the steering knuckle end, the control arm connects via ball joint to allow smooth wheel movement in all directions. The ball joint allows the steering knuckle to pivot and gives the wheels the ability to turn while the vehicle is in motion.


Many vehicles have an upper and a lower control arm for each front wheel, connecting to the highest and lowest steering knuckle points. This architecture makes for a more substantial assembly, ensuring balanced wheel control and stability.


However, there are exceptions to having a conventional upper/lower control arm layout. Vehicles with MacPherson-type suspension systems will only have a lower control arm, and a strut will replace the upper arm. Some cars with independent rear suspensions may have control arms at the rear wheels, but this is not a typical setup.