DIY: Rear Brakes on an Audi S4

1. Park the S4 on a level, flat surface. Use a tire iron to loosen the lug nuts that hold the rear wheels on. Lift the back of the car with a jack and lower it onto jack stands placed under the car at the proper places.
2. Finish removing the lug nuts and the wheels. Set the wheels out of the way. Remove the brake caliper spring clip on the outside of the caliper with a pair of pliers. Loosen and remove the caliper bolts located at the top and bottom of the brake caliper facing the wheel well.
3. Slide the caliper off the brake rotor. Support the brake rotor by tying it to a nearby suspension piece, so there is no weight on the soft brake line.
4. Remove the brake pads from the caliper and the caliper carrier. Disconnect the line for the brake wear sensor. Remove the bolts that hold the brake caliper carrier to the car. Set the carrier aside. Remove the brake rotor set screw, located in the face of the rotor. Pull the rotor straight off the hub.
5. Clean the area where the rotor mounts to the hub. Slide the new rotor onto the hub. Now is a good time to upgrade to cross-drilled rotors, which provide superior cooling. Install the rotor set screw. Bolt the caliper carrier back on.
6. Open the lid to the brake fluid reservoir located in the engine bay. Using a syringe, remove about ½-inch of the brake fluid. Place the Audi brake caliper tool over the piston in the caliper. The tool has metal dowels that fit into holes on the piston. Turn the tool so that it retracts and turns the piston into the caliper to make room for the new, thicker brake pads.
7. Install the new brake pads. Slide the caliper back over the new rotor. Install and tighten the caliper bolts. Connect the brake wear sensor, ensuring it is routed correctly. Reinstall the brake caliper clips. Repeat for the other side. Place the wheels back on the car and lower it. Fill the brake fluid reservoir with fresh brake fluid. Pump the brakes until the brake pedal feels firm again.