If the front brake pads are worn down, the rears are probably not far behind. Check them while doing the fronts. The rears DO NOT have wear sensors. When the brake pad backing plate comes in contact with the rotor and metal to metal contact is heard, you will know it's time to do the rears!
The following procedure shows the 1997 to 1999 US specification single piston design. However, the 2000 and later dual piston and four piston S8 deisgn would follow the same basic procedure.
Special Tools Required
- 7mm hex head tool, best to get one that will accept a 3/8" drive socket
- Large "C" clamp to push the piston back in the caliper
- Brake caliper lube
- Metric sockets, including a 17 and 18 mm
- Brake cleaner and rags
The following pictures are from Johnvey.com and the Bently manual. They identify the major brake components. The picture below denotes the "caliper bracket" it is refered to in this procedure as a "carrier bracket".
Take lug nut caps off and loosen lug nuts. Jack the car up and put front end up on jack stands. Raising the entire front end makes the job much simpler and safer. Remove wheel.
A8 Front Brake Assembly. Note where jack stand is located in upper left of picture.
Using a pair of pliers or screwdriver, remove the retaining spring (Figure 1, Item 9).
Remove the brake wear sensor electrical connection. It's a 90 degree turn to disengage.
Locate the two 7mm hex screw sockets in the back of the brake caliper (Figure 1, Item 2). Each has a plastic cap on it that has to be removed by prying it off with a flathead screwdriver. Unscrew the two hex screws.
Removing caliper screws. If you don't have a swiveling head 3/8" drive, this is a perfect excuse to buy one. You'll never understand why you didn't buy it sooner.
Close up of caliper screw removed. Note brake carrier bolt to the left. This will be removed if removing or replacing the rotor, if only doing the pads, the brake carrier does not have to be removed.
Remove the brake caliper from the caliper bracket. If the caliper seems to be stuck on, try grabbing the caliper and pulling it towards you, with a little force. That should retract the piston enough to loosen its grip on the rotor and allow you to remove the caliper.
When removing the caliper, tie it up with wire to relieve the stress on the brake line or rest it on the suspension arm. Don't let it hang from the brake line!
Remove the brake carrier bolts (2). This can be a little tricky to get adequate torque on the bolt to break it loose, so a cheater is made up using a large socket and a 3/8" extension. The swivel head rachet comes in handy to clear the body when using the cheater.
Remove the rotor. If it is rusted to the hub assembly, hit it with a rubber mallet on the top and bottom face (where the brake pads contact it) until it brakes loose.
Because the new pads are much thicker than the old pads, the piston will need to be pushed back into the caliper fully. Prior to doing this, check your brake fluid level. If it is high, it could overflow. You will need to remove brake fluid, if necessary. However, just watch it while pushing the piston back into the caliper. Use a "C" clamp and the old pad as a backing plate
Clean all components thourghly with brake cleaner and rags.
Installation of New Components
Prior to performing installation, take a break and wash your hands! Remove all grease from them. After grease is used in the following steps, wash them again, this will prevent grease contamination of the rotor pads and rotor surface. If you bought new rotors, clean the rotor off of all protective material and paint.
Evan Waterloo, using his Dad's DA sander to clean and scuff the surface of the rotors.
Prior to installing the new rotor, take some grease or caliper lube and put it on the hub where the rotor comes in contact. This will prevent the rotor from rusting to the hub assembly.
Install new rotor.
Install carrier bracket, torque to 92 lb-ft.
Lube the guide pins (Figure 1, Item 3) with brake caliper lube. The OEM Audi brake pads are marked with direction of rotation, ensure the correct pad is used for each side! Insert the inner pad into the caliper assembly.
If using OEM pads, they are marked for direction, ensure that the pad is situated for the correct direction!
Place the outer pad in the carrier assembly, and drop the caliper assembly down on it. If it doesn't want to fit on, you might not of pushed the piston all the way in. If this is the case, go back and push it all the way in.
Insert the two 7mm hex head screws. Ensure you start each one before tightening down. Cap the screws with the plastic caps. Hook up brake wear sensors, they are a 90 degree turn to install.
Insert the spring clip back into the caliper. Putting it back in is harder than getting it out. Make sure that it's completely seated.
Completed front brake job, look how clean everything is!
Sit in the car and slowly depress the brake pedal until it firms up. This is pushing the piston back out to its required position. Repeat other side. When complete, test drive your car around the block slowly. Take it easy on the brakes for the first couple of days or per manufacturer's instructions.