The original original brake discs are made of cast iron, which is used during daily use. It often rubs against the brake pads and looks very bright. But when parking for a long time, add Rain, humidity and other climates, the surface of the brake disc is easy to form rust spots, in fact, we There will be such a problem when buying a car to pick up a new car. The car will stop in the library for a while. This phenomenon, but this is not a malfunction, it has little effect on the braking force, and it is driving for a while.
After time, it will be automatically rubbed off.