2020-2022 Audi RSQ8 Brake Noise: Squeal, Grinding and Pulsation Causes

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake noise on a 2020-2022 Audi RS Q8 comes from one of three places: pads that have glazed or were never bedded in (squeal), pads worn down to the backing plate or a stone trapped against the disc (grinding), and uneven pad material on the discs (pulsation you feel in the pedal or steering wheel). The fix depends on which brake system your RS Q8 has, because the standard iron-disc RS brakes and the optional RS ceramic brakes are serviced very differently.

How the RS Q8 Brake System Is Built

Audi describes the RS Q8's standard RS braking system as ventilated composite discs measuring 420 millimeters in front and 370 millimeters in the rear, with a 10-piston caliper system on the front axle. The calipers come in black as standard, with a red finish as an option. Audi also offered RS ceramic brakes as an option on the RS Q8, and those use a 440 mm front disc and a 370 mm rear disc.

That size difference matters for noise diagnosis. A very heavy, very fast SUV pushes a lot of heat through these parts, and big multi-piston calipers with large pads are more prone to vibration-type squeal if the pad backing, shims or abutment surfaces are dry or dirty. Before you buy anything, confirm which system you have: look at the disc diameter, the caliper color and the build sheet or window sticker. Parts for the 420 mm iron system do not fit the 440 mm ceramic system, and pads designed for iron discs should not be used on carbon-ceramic discs.

Squeal: What It Means and How to Diagnose It

A high-pitched squeal is a vibration: the pad and disc excite each other at a frequency you can hear. On the RS Q8 the most common triggers are:

• Glazed pads. Long, gentle stops or dragging the brakes down a grade can cook the pad surface into a hard, shiny layer that sings instead of gripping.
• Pads that were never bedded in. New pads need an even layer of friction material laid down on the discs. Skip that step and the contact is patchy, which can squeal and later pulse.
• Dry or missing anti-noise hardware. Worn shims, missing spring clips, or dry pad ears in the caliper let the pad buzz against the caliper body.
• Wear warning. If your pads use a wear sensor, the dash warning usually arrives before the noise. A constant squeal plus a brake-pad warning light means it is time for pads now.

To diagnose, note when it happens. Squeal only on the first few cold stops in the morning, which then goes away, is often moisture and surface rust and is normal. Squeal on every light stop, warm or cold, points to glazing or hardware. Squeal that changes when you press harder is usually vibration at the pad backing and responds to new shims and fresh caliper lubricant on the contact points.

Grinding: Stop Driving and Inspect

Grinding is metal on metal or a foreign object, and it should never be ignored on a vehicle this heavy.

• Pads worn to the backing plate. The steel backing scrapes the disc, cuts grooves into it and can overheat the caliper pistons. Pads and discs will both need replacing.
• A stone or debris between the dust shield and disc. This makes a scraping or grinding sound that can come and go while driving, even off the brake. Pulling the wheel and removing the debris often cures it.
• Bent dust shield. A shield knocked inward during a tire change can rub the disc edge.
• Heavy rust after sitting. A car parked for weeks grinds on the first few stops as the rust ring scrubs off. If it continues after a short drive, inspect.

With the wheel off, look through the caliper at the pad thickness on both the inner and outer pad. The inner pad often wears faster and is the one you cannot see from outside the wheel.

Pulsation: Why the Pedal or Steering Wheel Shakes

Pulsation is almost never a disc that is literally warped. It is usually uneven friction material on the disc face. Power Stop explains that when pads are not broken in, pad material deposits in random, uneven spots on the rotors, and the result is pulsing in the pedal, shaking of the vehicle and vibration in the steering wheel.

Other causes to check:

• Runout at the hub. Rust or debris between the disc hat and the hub face makes the disc wobble slightly. Over thousands of miles that wobble turns into thickness variation you can feel. Clean the hub face down to bare metal every time a disc comes off.
• Uneven wheel bolt torque. Impact-gunned wheel bolts can distort the disc hat. Tighten in a star pattern with a torque wrench to the value in the factory service manual.
• Holding the brakes after a hard stop. Sitting at a light with the pedal clamped on a very hot disc can print a pad-shaped patch of material onto it.

If the vibration shows up in the steering wheel it is usually the front; if you feel it more in the seat or through the body, suspect the rear.

The Fix: Which Parts to Replace

For the standard iron-disc system, most noise complaints are solved with fresh pads, a correct bed-in, and new or resurfaced discs if they are grooved, below minimum thickness, or have uneven deposits that will not clean up. For a street-and-track pad upgrade on the iron-disc system, we carry the EBC Yellowstuff front brake pads for the 2020-2022 Audi RS Q8 4.0 twin-turbo. Whatever pad you choose, follow its bed-in instructions fully; an incomplete bed-in can create the very pulsation you were trying to cure. Brembo also points out that noise after a pad change is often caused by other worn parts in the system rather than the new pads, so inspect caliper pistons, seals, boots and sliding parts, fit new shims instead of reusing old ones, and put anti-noise grease on the contact points between bracket and pad. Brembo gives a disc runout limit of 0.10 mm and a hub runout limit of 0.050 mm as the values to check against.

Browse more options in our brake pads collection and brake rotors collection. For the ceramic system, pads and discs are specialized parts; have a dealer or carbon-ceramic specialist confirm the correct components.

What to Replace at the Same Time and How Hard the Job Is

When you do RS Q8 front pads, plan on:

• New pad shims and spring clips, or the hardware that comes with the pads, available in our brake hardware kits.
• New wear sensors if yours are fitted, since most are single-use once they have triggered.
• Fresh brake fluid if it is due by Audi's maintenance schedule; old fluid does not cause noise, but a brake job is a sensible time to flush it.
• Cleaning the hub faces and caliper abutments, and a thin film of brake-specific lubricant on the pad ears and backing contact points only, never on the friction surface.

On the iron-disc system this is a moderate DIY job for someone with a torque wrench, a scan tool, and a way to push back ten front pistons evenly. If your rear calipers carry electric parking brake motors (the parking brake is a console switch rather than a lever or pedal), put them into service mode with a scan tool before pushing the rear pistons back; forcing them can damage the motor. The wheels and discs are large and heavy, so a second set of hands helps. After installation, bed the pads in. Power Stop's general procedure is five moderate to aggressive stops from 40 mph down to 10 mph in rapid succession without stopping fully, then five moderate stops from 35 mph down to 5 mph, then about five minutes of driving at moderate speed to let everything cool without coming to a full stop on hot brakes. Always follow the specific instructions that come with your pads, and do bedding stops only where it is safe and legal.

Frequently Asked Questions

Why do my RS Q8 brakes squeal only in the morning?

Overnight moisture leaves a thin layer of surface rust on iron discs. The first few stops scrub it off and the noise fades. If it lasts beyond the first few stops, look for glazing or dry pad hardware.

Are my RS Q8 rotors warped if the steering wheel shakes when braking?

Usually not. Most pulsation comes from uneven pad deposits or thickness variation that started with hub runout. Resurfacing or replacing the discs, cleaning the hubs and bedding new pads correctly normally cures it.

Can I put performance pads on an RS Q8 with ceramic brakes?

Only pads made specifically for the carbon-ceramic discs. Pads for the 420 mm iron system do not fit the 440 mm ceramic system, and iron-disc compounds should not be used on ceramic discs.

How do I tell which brake system my RS Q8 has?

Check the disc size, the caliper color and your window sticker or build sheet. Audi lists the standard calipers in black or optional red, and the ceramic option with a 440 mm front disc.

Why are my new RS Q8 pads noisy right after installation?

Brembo notes that noise after a pad change usually comes from worn surrounding parts rather than the new pads. Reused shims, tired caliper springs, dry contact points and hub runout are the usual suspects, along with an incomplete bed-in.

Sources

1. Audi press release: RS Q8 performance and updated RS Q8 - RS brake system with 420 mm front and 370 mm rear discs, 10-piston front calipers, caliper colors, RS ceramic option with 440 mm and 370 mm discs
2. Brembo: Noises and vibrations - noise from worn system components, disc and hub runout limits, shims, springs and anti-noise grease
3. Power Stop: What is the break-in procedure? - bed-in steps and how skipping them causes uneven deposits, pedal pulsation and steering vibration