Genuine BMW 34216765891 Disc Brake Rotor; Rear; 370x24mm – BMW | 150.3440.20 34216864048 W01331898872

Brake discs or brake rotors are discs made of iron, steel, ceramic, or carbon fiber with a cylinder hub/hat and drilled plate that attach to the lugs around a wheel hub and are used to slow the wheel to a stop. Brake discs function by having brake pads clamped to either side of the disc to create friction and slow the wheel. Brake discs are also used in the function of the parking brake to hold the wheels still when parked.

The friction created to slow the wheel creates a lot of heat that, overtime, can warp the brake discs and glaze the faces of the discs contacted by the brake pads. This results in the pads being unable to grip the brake discs as well as they should and increasing the time it takes for the wheels of your BMW to slow to a stop.

Replacing Your BMW Brake Discs
Sometimes the faces of the brake discs can be resurfaced for them to adequately slow the wheel. However, resurfacing a brake disc thins the face, leaving it susceptible to warping quickly. It is always recommended to replace warped brake discs or brake discs with glazed faces to ensure the quickest and safest stop possible.

Brake discs should always be replaced along with new brake pads. When replacing brake discs and pads there is a bedding process to properly mate the new brake pads to the brake discs faces.

• Accelerate to 35mph and use moderate brake pedal pressure to slow your BMW to 5mph, repeating this process up to three times.
• Next, accelerate to 55mph and use strong brake pedal pressure to slow your BMW to 5mph without engaging the anti-lock brakes, repeating this process up to five times.
• Lastly, drive slowly for five to ten minutes using light brake pedal pressure when coming to stops to allow the brakes to slowly cool down before parking the vehicle for about an hour to let the brakes completely cool.

BMW Brake Discs.