Brake components for German cars have changed quite a bit over the past decade but the basic principals are still the same. Back when automobile manufacturers cared less about weight, fuel economy and performance, brake components were built to be heavy and strong. The excessive mass of the rotors allowed room for them to be machined or “cut” down, in order to smooth them out and reuse the rotors when the brake pads need to be replaced.
These days, rotors are designed to weigh less, increase performance and reduce fuel consumption. Automobile manufacturers have reduced not only the weight, but the overall thickness of the rotor. The reduction in unsprung mass is noticeable on modern cars and has achieved the goal the engineers intended. However, modern brake rotors cannot be machined as they are too thin to remove any high spots or groves [...]