What Are the Control Arms for Car Suspension?

The white bar running front to rear is this car's control arm.

Control arms are the primary load-bearing elements on any suspension, and their size and geometry are crucial for determining the acceleration, braking and handling characteristics.

Location

The suspension's control arms connect the chassis to either the wheels (on an independently suspended axle), or the axle tube itself on solid axle applications.

Purpose

Control arms allow the suspension to move up, down, back and forth in a manner determined by their geometry.

Lateral and Longitudinal

Lateral control arms connect to the chassis and point outward, as in double-A arm and MacPherson strut suspensions. Longitudinal control arms control up and down movement of an axle, and are found on four-link and five-link rear suspensions.

Strut Suspensions

Strut suspensions use only a single control arm on the bottom; the strut (a combination spring and shock absorber) acts as the upper control arm.

One of a Kind

Control arms are almost always used with coil springs. The only current exception is the Chevrolet Corvette, which uses rear control arms and a single leaf spring that runs from side to side and is connected to the chassis in the middle.

References

• 240edge.com: Suspension Tuning
• Carbibles.com: The Suspension Bible