Brake shield
Protects the disc from debris and guides cooling air.
Behind each brake disc, bolted to the hub carrier.
A thin pressed plate blocks stones and water spray; M cars may add ducts that feed air to the disc.
A mudguard for the brake.
A scraping noise after driving on gravel often comes from a bent shield touching the disc.
Pads and discs are measured wear items. Driving, environment and regenerative braking change wear; use the actual inspection limits.
Ordinary friction service differs greatly from carbon-ceramic replacement or hydraulic-controller work; obtain a vehicle-specific quote.
Some BMW M cars route air from the front bumper to the discs for repeated hard stops.
BMW models with hydraulic friction brakes; performance equipment and parking-brake design vary.