Control arm bushings are the pivot points of your suspension. They mount the control arms to the vehicle frame. The bushing consists of a rubber cylinder bonded between an inner steel sleeve and an outer metal shell. When you drive over bumps, the rubber twists to let the control arm swing up and down. This isolates the cabin from harsh metal impact shocks and vibrations, keeping the ride quiet.
Because they support the weight and force of braking, bushings take a beating. Rubber rots and tears over time, letting the control arm shift. This causes wheel alignment problems, uneven tire wear, and a clunking noise when you apply the brakes or drive over bumps. Replacing them requires a shop press to drive the old bushing out of the arm.