Brake Backing Plate
A metal shield mounted behind the brake rotor or drum to protect the brake assembly from debris and water.
A brake backing plate, also called a brake dust shield, is a thin metal plate bolted to the wheel hub or axle housing directly behind the brake rotor or inside the brake drum. Its primary function is to protect the braking components from road hazards, such as splashing water, mud, rocks, and road salt.
It also helps channel cooling air over the rotor and prevents hot brake dust from coating suspension components. On drum brake systems, the backing plate is a structural component that mounts the wheel cylinder and brake shoes.
Over years of exposure to moisture and road salt, metal backing plates can rust, disintegrate, or warp. A warped or rusted backing plate can bend and rub against the spinning brake rotor, generating a scraping or squealing noise. Replacing a rusted backing plate typically requires removing the wheel hub or axle shaft.