Brake disc
Provides the friction surface that the pads grip.
Bolted at the wheel hub inside the wheel.
Friction converts vehicle motion to heat; ventilated designs add internal air passages.
A rotating plate squeezed to slow the wheel.
Vibration, scoring or thickness loss need measurement and checks of hubs, tires and suspension.
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.
BMW brake-disc size and construction depend on the fitted brake package, not just wheel size.
BMW models with hydraulic friction brakes; performance equipment and parking-brake design vary.