Your brakes can be thought of as a device for converting movement into heat. As your BMW slows down, all of that kinetic energy has to go somewhere and most of it ends up as heat. In other terms, all that friction between the brake pads and the rotor generates heat in much the same way that striking a match generates heat. If too much heat builds up, the brakes begin to fade and become less effective. The better ventilated the brake calipers are the better they perform. Get yourself a new set of brake caliper for your BMW F15 X5 (2014+) with us.