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BMW's are equipped with some of the finest braking equipment found on production cars. When replacing any portion of the braking system, use original quality parts. Use components approved by BMW to maintain the high standards set by the manufacturer. Brakes are no place to skimp on quality.
Brakes have more power than the engine. This is best demonstrated by the fact that a vehicle can stop in a shorter distance from a given speed than the vehicle took to accelerate to that speed. Examining the capacity of the braking system to dissipate energy from this point of view gives a new respect for the incredible job the braking system must perform and the reasons the braking system should be maintained to the highest standards.
BMW does not recommend the use of brake dust shields. The shields that mount between the wheel and the hub can block the flow of cooling air. All the energy dissipated by the brake rotors is in the form of heat. Air flow must be maintained through the wheel to prevent warping of the rotors and fading of the brakes. If brake dust on the wheels is a problem, there are high quality, high performance brake pads available from the aftermarket that give off less brake dust than original equipment brake pads.
New materials and construction of brake pads have allowed racing levels of brake performance from street usable brake pads. Carbon formulations and metallic brake pads have shown exceptional levels of performance with few of the drawbacks once found in high performance brake pads. Old style, high performance brake pad formulations needed to be heated by use before they would start to give any performance. These old style pads would hardly stop the car on a cold day until brake application brought the pad temperature up to the working range. The new formulations work hot and cold and wear the rotor little.
Brake rotors are a wear item and should be replaced if found to grooved, warped or worn below the minimum thickness. The more metal a rotor has, the more heat the rotor can absorb, then reject without warping. As the rotor wears, the amount of metal in the rotor is reduced along with the heat absorbing capacity. Rotors can be ground to restore a smooth surface, but it is better to replace the rotors with new. Always replace the rotors and pads in pairs to maintain braking balance.