Trinity Autosport sells a wide array of brake performance parts for your BMW E9x (2006-2013). We sell calipers for disc brake system. When you press the brake pedal, the brake fluid flows from the master cylinder to the calipers. Brake fluid then applies pressure on the piston inside the caliper, pushing the brake pads against the rotors to slow/stop your car. A car can have either 2 or 4 calipers. If your E9x (2006-2013) has rotors on all four tires, then it will have four calipers. If your car has two rotors and two drums, then it will have two calipers in front. The calipers can become contaminated, rusty, and start to leak brake fluid – when that happens you may need to replace the calipers. Shop from our selection of brake performance parts today!