Why did the brake disc turn black?

[DeHaley]

The blackening of the brake disc indicates severe oxidation, and it needs to be replaced promptly. More knowledge about brake discs is as follows: 1. Overview: The brake disc is a round disc that rotates as the vehicle moves. The brake caliper clamps the brake disc to generate braking force. When the brake is applied, it clamps the brake disc to slow down or stop the vehicle. Brake discs offer excellent braking performance and are easier to maintain than drum brakes. 2. Features: Brakes include disc brakes, drum brakes, and air brakes. Older vehicles often have disc brakes in the front and drum brakes in the rear, while many newer vehicles have disc brakes on both front and rear wheels. Disc brakes dissipate heat better than drum brakes, making them less prone to thermal fade during high-speed braking, thus providing superior high-speed braking performance. However, their braking effectiveness is inferior to drum brakes during low-speed cold braking.