TO №2
On rear disc brakes, pad wear is monitored in the same way as on the front. The wear limit here is 7 mm - with the thickness of the carrier plate, while the width of the lining itself is 2 mm.
Simultaneously with the control of pad wear, the condition of the brake discs is checked. Wear rates and sequence of work are the same as when checking the front disc brakes.
In addition to the pads themselves, four self-locking bolts are required, which are usually included with the pads.
Replacing the rear disc brake pads
Although the job is easy to do, you may still run into problems if the special key 3131 or 3232 from the Audi workshop is not available. The following description, therefore, can only help if you can rent this key from a workshop or make it according to a model.
Unscrew both fixing bolts of the disc brake caliper housing, while holding the guide bolt by the hexagon.
Pull the caliper body towards the outside of the vehicle by hand.
Now fold it back and take it off.
Remove brake pads from guides.
Install the special wrench 3131 or 3232 to the brake piston and screw in the piston with strong hand pressure.
Ask an assistant to monitor the level of brake fluid in the reservoir. If the tank overflows, it is necessary to pump out the liquid.
Left: Measuring pad thickness on rear disc brakes. The lining material on the brake pads must not be thinner than 2 mm (a = 2 mm).
Right: loosening the fixing bolt (2) to remove the rear disc brake caliper. Guide bolt (1) should stick with an open end wrench. Use new self-locking bolts for installation.
Left: for changing brake pads (1) remove brake caliper housing (3) rear disc brakes. Finally, the brake piston (2) must be returned to its original position.
Right: this is done, as shown in the picture, using the special key 3131 from the Audi workshop.
Never retract the brake piston without force rotation. In this case, you will destroy the adjusting mechanism in the piston.
Install new pads.
Tighten disc brake caliper housing with new self-locking bolts to 35 Nm.
Use only a thin open end wrench to hold the guide bolt. The wide one can jam, in which case the tightening force will not match.
After dismantling the brake mechanism, it is imperative to make a basic adjustment.
Rear wheel disc brake adjustment
Raise the vehicle at the rear on both sides and secure. Remove wheels.
Remove parking brake.
Check that the cable drives of the parking brake system are not preloaded:
To control, press the lever for engaging the parking brake system on the brake caliper alternately to the right and left until it stops.
If the brake caliper lever on the other wheel also moves, the parking brake cables are too tight. In this case, loosen the central adjusting nut of the parking brake system until both levers reach exactly against the stop.
Front-wheel drive vehicles: Press the brake force regulator control lever where the spring is connected to the stop in the direction of the spring tension.
Have an assistant depress the brake pedal twice with moderate force while the engine is off.
Release the lever again.
Four-wheel drive vehicles: between the tension spring of the regulator and its (her) insert a drill bit with a minimum thickness of 6 mm on the rear axle. The spring is thus stretched.
With the engine off, depress the brake pedal twice with moderate force.
Remove drill.
Vehicles with ride height control: put the vehicle on its wheels.
Start the engine and let it idle for about 2 minutes.
Stop engine.
With the engine off, depress the brake pedal twice with moderate force.
Raise the vehicle again.
For everyone: check that both rear wheels can turn freely.
Removing the rear disc brake caliper
Disconnect the brake hose if the brake caliper needs to be replaced.
Remove the brake caliper housing as for replacing the pads. Pay attention to the text above!
Remove the cable drives of the parking brake system.
Unscrew both fixing bolts of the caliper located on the axle.
When installing, tighten the caliper mounting bolts to 65 Nm.
When installing the caliper body, pay attention to the instructions above.
Carry out the adjustment again.
Replacement of cuffs of back brake cylinders. Replacing the rear brake disc
Replacing defective brake piston seals on the rear disc brake calipers is the same as on the front ones.
Remove the disc brake caliper.
Remove brake disc.
Clean the contact surface on the wheel hub or clean with fine sandpaper and put on a new brake disc.
Carry out the adjustment according to the described scheme.
Basic rear wheel brake adjustment:
Left: to check if the parking brake cables are not tight, press the parking brake lever (1) on calipers on the right and left to the stop (arrows). If the lever on the opposite caliper also moves, then the parking brake cables are too tight.
Right: what is shown in the picture on the left for a front wheel drive vehicle is shown here again for the Audi-100 quattro. The caliper lever with the parking brake released should not rise from the stopper, which is indicated here by arrows and the distance is shown «A».
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