The E70 X5 and the E71 X6 both have impressive braking capabilities, especially when you consider the sheer size and weight of these vehicles. BMW achieved this feat by using a combination of softer composite brake discs together with a pad compound that, although very effective, unfortunately causes the rotors wear down to their minimum effective thickness at a quicker rate than most. Brake rotors on bigger cars can also become easily worn due to the weight of the vehicle. To ensure your car's braking performance is upheld, we recommend replacement with Zimmermann discs. As an original equipment supplier to BMW, Zimmermann's discs are manufactured to the highest standards in Germany and come with their own Z-Coat to prevent the common problem of surface rust.