Control arm

In simple terms, it governs a wheel's vertical travel, allowing it to move up or down when driving over bumps, into potholes, or otherwise reacting to the irregularities of a road surface.

It can thus control the position of the outboard end in only a single degree of freedom, maintaining the radial distance from the inboard mount.

These constrain the outboard end of the wishbone from moving back and forth, controlling two degrees of freedom, and without requiring additional links.

A double wishbone design features both upper and lower control arms that work in tandem with each other to properly locate the wheel.

Control arms are most commonly encountered as part of the MacPherson strut independent front suspension.