The BMW M Performance sports brake system is only approved in combination with at least 18" aluminum wheels. Brembo high-performance 4-piston aluminum fixed caliper on the front axle and 2-piston aluminum fixed caliper on the rear axle. Improved thermal resistance thanks to larger, internally-ventilated, lightweight-construction sports brake discs. Drilled (dimpled) and grooved brake discs also reduce water film build-up between the brake lining and the disc surface. Available in M Performance Red, Yellow or Orange GÇô all with an M logo on the outside of the caliper. Drilled and grooved, internally-ventilated lightweight brake disks with riveted aluminum hat measuring 370 x 30 mm (diameter x thickness) on the front axle and 345 x 24 mm on the rear axle (rear brake discs must be ordered separately).