2006-2009 Audi RS4 Parking Brake Problems and Adjustment

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2006-2009 Audi RS4 (B7) uses a simple, cable-operated parking brake that works through the rear brake calipers, not a separate drum. Most RS4 parking brake problems come down to three things: a rear caliper whose internal self-adjuster has stopped working, a cable that is stretched, seized or binding, or a caliper piston that was pushed back instead of screwed back during a pad change. Here is how the system works, how to tell which fault you have, and how to fix it without creating a new one.

How the RS4 Parking Brake Works

The B7 RS4 pairs huge front brakes with a much simpler rear. Up front it uses 365 mm two-piece, cross-drilled and vented rotors with Brembo eight-piston monobloc calipers. At the rear, Audi increased the rotor diameter to 324 mm but kept single-piston floating calipers. That rear single-piston floating caliper is the key to the whole parking brake, because the handbrake mechanism is built into it.

When you pull the handbrake lever, cables run back to a lever arm on each rear caliper. Rotating that arm turns a threaded mechanism inside the caliper, which drives the piston forward and clamps the pads against the rotor. Under normal driving, hydraulic pressure from the pedal moves the same piston. A ratchet-style self-adjuster inside the caliper takes up pad wear so the handbrake lever travel stays consistent as the pads get thinner.

Because the parking brake shares the rear pads and rotor, anything that affects the rear caliper affects the handbrake, and anything wrong with the handbrake mechanism can cause rear brake drag.

Symptoms and What They Point To

• Handbrake lever pulls up too far or will not hold the car on a hill. Most often the caliper self-adjusters are not taking up pad wear, or a cable has stretched. It can also mean the rear pads are worn out or glazed.
• Handbrake holds on one side only. Usually one cable is seized in its housing or one caliper lever arm is stuck. Safely support the rear and spin each wheel with the lever pulled a few clicks to find the weak side.
• Rear brake drags, one rear wheel runs hot, or the car feels like it is pulling against the brakes after the handbrake is released. The caliper lever arm is not returning fully to its stop, the cable is binding, or the adjuster mechanism is sticking. Technician guidance on VW and Audi integral-parking-brake calipers notes the mechanism can stick from debris in the arm.
• Long rear pedal travel or a high handbrake right after a pad change. The self-adjuster has not taken up the new clearance yet. Several firm pedal applications and a few handbrake pulls usually bring it back; if not, the adjuster may be damaged.
• Brake warning light stays on with the lever down. Check the lever switch and the brake fluid level, since low fluid can trigger the same warning.

Causes

Rear caliper self-adjuster failure

The ratchet inside the caliper is meant to adjust automatically, but it can fail after a pad replacement or stick from corrosion and debris. On a car that sees little use, as many RS4s now do, the mechanism can seize from sitting. Once the adjuster stops working, no amount of cable tightening will give a correct handbrake for long.

Piston pushed instead of screwed back

Like other VW and Audi rear calipers with an integral parking brake, the RS4 rear piston must be rotated back into its bore in small steps with a caliper retracting tool, not simply pushed. Forcing it straight back with a C-clamp can damage the internal mechanism. This is the most common way a working parking brake gets broken during a routine rear pad job.

Cable wear and binding

The cables pass under the car and are exposed to road salt and water. A cable that is rusty inside its sheath will pull on but not release fully, which keeps the caliper arm partly applied and heats the rear brake.

Worn or glazed rear pads and rotors

A handbrake can only clamp as well as the friction surface allows. Glazed pads or a lipped, heat-checked rotor reduce holding force even if the mechanism is perfect.

How to Adjust and Fix It

On this design the rear calipers are self-adjusting, so the cable is not something you tighten every time the lever feels high. Cable adjustment is a set-up step after replacing a cable, caliper or rotor, and it only works if the caliper adjusters are working. The correct order is:

1. Inspect the rear brakes first. Check pad thickness and rotor condition. Replace anything worn before touching the cable.
2. Confirm each caliper lever arm moves freely and returns to its stop. With the handbrake fully released, the arm should rest against its stop on both sides. If an arm is sticking, the caliper or cable needs attention.
3. Reset the pistons correctly. When fitting new pads, screw the piston back in with a proper retracting tool until it bottoms out, turning it in small steps and aligning the piston as the service information shows.
4. Let the adjusters take up clearance. After the pads are in, press the brake pedal firmly several times, then apply and release the handbrake several times.
5. Set cable tension only if needed. Follow the procedure and clearance in the factory service manual. The goal is cables with no slack that still let both caliper arms rest on their stops when released. Over-tightening holds the arms off their stops and causes rear drag and overheating.
6. Test. Both rear wheels should turn freely with the lever released and lock with the lever pulled a few clicks. Road test and check that neither rear wheel is noticeably hotter than the other.

If a caliper will not self-adjust after a correct reset, or its lever arm is seized, replace the caliper. Rebuilding the internal adjuster is rarely worth the labor. See our replacement brake calipers and the brake hardware kits for clips and slide pin parts.

What to Replace at the Same Time

• Rear pads and rotors as a pair across the axle. If the parking brake has been dragging, the rear rotors are often heat-marked. Browse brake rotors and brake pads, and match the rotor diameter to your car before ordering.
• Both parking brake cables if one has seized. The other has seen the same salt and age.
• Slide pins and boots on the rear caliper carriers, cleaned and lubricated with high-temperature silicone grease.
• Brake fluid if it has not been changed recently, since you will be opening the system if a caliper is replaced.
• Front pads if you are doing a full brake service. For the front 8-piston calipers we carry the EBC Redstuff ceramic low-dust front pads for street driving and the EBC Yellowstuff street and track front pads for cars that see track days, both for RS4s with cast iron rotors.

A Warning About Rear Big Brake Kits

Many RS4 owners consider a rear big brake kit. Be aware that the Brembo GT 4-piston rear kits built for the B7 RS4 use opposed-piston calipers with no parking brake mechanism. Product descriptions for these kits state the system eliminates the parking and emergency brake function and is not for road use. Our Brembo GT rear big brake kit for the 2006-2008 RS4 is a track-focused part for that reason. If your RS4 is a street car that needs a working handbrake, keep the factory rear calipers and upgrade pads and rotors instead.

How Hard Is the Job?

Diagnosing a sticking handbrake and resetting rear pistons is a moderate home job if you own a proper rear caliper retracting tool, jack stands and a torque wrench. Cable replacement is harder because the cables run along the underbody near the exhaust and heat shields. Caliper replacement means opening the hydraulic system and bleeding the brakes, which on an ABS and ESP equipped car should be done carefully so no air reaches the hydraulic unit. Torque all caliper and carrier bolts to the values in the factory service manual.

Frequently Asked Questions

Does the Audi RS4 B7 have an electronic parking brake?

No. The B7 RS4 uses a hand lever and cables that operate a mechanism built into the single-piston rear calipers.

Why does my RS4 handbrake lever come up so high?

Usually the rear caliper self-adjusters are not taking up pad wear, the rear pads are worn, or a cable has stretched. Check pads and adjusters before tightening the cable.

Can I push the rear caliper piston back with a C-clamp?

No. The rear piston must be screwed back in with a retracting tool. Pushing it straight in can damage the parking brake mechanism inside the caliper.

Will a Brembo rear big brake kit keep my parking brake?

The Brembo GT 4-piston rear kits for the B7 RS4 do not retain the factory handbrake. They are intended for track use.

Why is one rear wheel hot after driving?

A caliper lever arm that is not returning to its stop, a binding cable, or an over-tightened cable can keep that rear brake lightly applied. Release the handbrake and check that both arms rest on their stops.

Sources

1. Supercar Nostalgia: Audi B7 RS4 guide - 365 mm front rotors, eight-piston monobloc calipers, 324 mm rear rotors, single-piston floating rear calipers
2. AP Racing: Audi RS4 (B7) front disc kit - 365 x 34 mm front disc, OEM Brembo eight-piston calipers
3. Tarox rear discs for Audi RS4 Quattro (B7) - 324 mm rear disc size
4. Tomorrow's Technician: VW rear disc brake piston retraction - integral parking brake ratchet adjuster, turn-to-retract pistons, sticking mechanism, slide pin lubrication
5. Brembo GT rear kit for Audi RS4 B7 listing - kit eliminates parking brake function, not for road use
6. TDI: Audi RS4 B7 Brembo rear brake kit - kit does not retain the OEM handbrake