Bump Stop
A rubber or polyurethane cushion designed to prevent metal-on-metal bottoming out of the suspension.
A bump stop (also known as a jounce bumper) is a small rubber, polyurethane, or microcellular foam cushion mounted on the vehicle suspension system, typically surrounding the shock absorber piston rod or attached to the frame above the axle. Its primary function is to act as a progressive cushion when the suspension reaches its maximum travel, preventing metal-on-metal bottoming out.
When a vehicle hits a severe pothole or carries a heavy load, the suspension compresses. Just before the coil spring fully compresses or the control arm hits the frame, it contacts the bump stop. The bump stop absorbs the remaining impact energy, protecting structural suspension brackets, shock absorbers, and the chassis from damage while reducing the harshness felt by passengers.
Over time, exposure to oil, road grime, and constant compression cycles causes bump stops to rot, crumble, or fall off. A missing or damaged bump stop will result in a loud, metallic clunking sound when driving over large bumps and can cause premature failure of the shock absorbers and control arms.