An abutment is a critical load-bearing contact point where mechanical components meet. In car brake systems, the caliper bracket has abutment slots that support the brake pads. These slots take the rotational force of the brake pads when they squeeze the spinning rotor.
These metal-on-metal contact points must remain clean and lubriced. Stainless steel shims or clips are placed in the abutments to provide a smooth sliding surface. If rust builds up here, the pads can get stuck, causing uneven wear and dragging brakes.
During brake jobs, mechanics must file or wire-brush the bracket abutment surfaces. Removing rust scale ensures the new pads slide freely. A small amount of silicone grease on the tabs completes the assembly and prevents brake squeal.