2021-2022 Audi Brake Pulsation Diagnostic Guidelines

Important Note for Owners

Audi has issued a specific warning regarding the use of this Technical Service Bulletin:

"DO NOT use this TSB if there is another TSB for same concern applicable to the VIN. This TSB is only intended for diagnostic purposes and does not serve as a guideline for determining warrantable conditions."

This means the TSB is a diagnostic aid for technicians and does not guarantee warranty coverage for repairs.

Symptoms of Brake Pulsation

Owners of 2021-2022 Audi vehicles, including the Audi e-tron, may experience the following symptoms related to brake pulsation:

• The steering wheel vibrates or pulsates when the brakes are applied.

Technical Background: Why Brakes Pulsate

Brake-related vibrations and pulsations can have multiple root causes. These include factors such as driving style, environmental conditions, and the vehicle's service history. As brake pads and discs wear over time, their dampening ability naturally decreases.

A common contributor to brake pulsation is Disc Thickness Variation (DTV). DTV occurs when the two braking surfaces of a brake disc are no longer parallel. This condition is difficult to measure accurately with standard workshop tools. The presence of DTV can lead to the noticeable Audi e-tron brake pulsation.

Common Causes of Brake Pulsation

Several conditions can lead to brake pulsation. Proper diagnosis often requires a test drive under conditions similar to when the customer experiences the issue (e.g., specific speed, braking pressure, and component temperature).

Overheated Brake Components

Overheated brake components can cause permanent damage to both brake discs and pads. This often results from an overly aggressive driving style involving frequent sharp braking without adequate cooling periods.

• Condition: Brake pad material smeared on the brake disc (Figure 2 in the original document). This can create DTV.
• Service: If this condition is identified, the brake discs and pads should be replaced.

Blue-Tempered or Overheated Brake Discs

Discs that appear blue-tempered or show signs of overheating indicate excessive heat. This can be caused by a faulty component leading to constant brake application or aggressive driving.

• Condition: Blue-tempered or overheated brake discs (Figure 3 in the original document).
• Service: Replace the brake disc and pads if this condition is present.

Corrosion/Rust Build-up

Corrosion or rust on brake discs can impact their ability to function correctly and, if left unaddressed, can cause permanent damage. This condition can create DTV.

• Condition: Corrosion/rust build-up on the brake discs (Figure 4 in the original document).
• Common Causes: Exposure to road salt, high humidity, moisture, or the vehicle not being driven for extended periods. A gentle driving style might not be enough to remove this build-up.
• Service: Technicians may attempt 2-3 ABS stops from speeds above 50 mph, allowing components to cool between stops. If the condition persists, replace the brake discs and pads.

Pad Material Transfer or Corrosion Marks

Marks from brake pads or corrosion on the brake disc (Figure 5 in the original document) can also create DTV.

• Condition: Pad material transfer or corrosion marks from brake pads on the brake disc.
• Common Causes: Vehicle not driven for a prolonged period, or brakes exposed to high humidity/moisture.
• Service: Similar to corrosion, technicians may perform ABS stops to try and clear the marks. If unsuccessful, replace the brake disc and pads.

Excessive Brake Disc or Wheel Hub Run-out

Excessive run-out in the brake disc or wheel hub can lead to significant vibration, contributing to the Audi e-tron brake pulsation. This condition needs to be measured according to specific instructions.

• Condition: Excessive brake disc or wheel hub run-out (Figure 6 in the original document).
• Common Causes: Over-torqued or improperly torqued wheels, non-Audi approved wheels with incorrect contact surfaces or center bore dimensions, or external impact/rust build-up between the brake disc and hub.
• Service: If measurements exceed maximum values, replace the brake disc(s) and/or hub(s).

Worn Brake Pads

As brake pads reach their wear limit, their ability to dampen vibrations is reduced, leading to pulsation.

• Condition: Worn brake pads (Figure 7 in the original document).
• Service: Replace worn brake pads and discs.

Faulty Suspension Components

Damaged or aftermarket suspension components can amplify vibrations or lead to body vibrations that become noticeable during braking.

• Condition: Faulty, damaged, or aftermarket suspension components such as ball joints, links, tie rods, or bushings (Figure 8 and Figure 9 in the original document).
• Service: Diagnose and address these components accordingly.

Wheel/Tire Imbalance

Imbalance or radial run-out in wheels and tires can also significantly amplify vibrations or cause body vibrations during braking.

• Condition: Wheel/tire imbalance or radial run-out (Figure 10 in the original document).
• Service: Inspect and diagnose these components accordingly.

Brake Run-out Measurement Guidelines

To accurately measure run-out, specific conditions must be met:

• All measured surfaces must be free of rust, corrosion, or pad material transfer.
• A specialized tool, such as the VAS6079/1, must be securely attached to a solid suspension component (Figure 11 in the original document).
• The brake disc must be secured to the hub with five bolts.
• The axle bolt/nut must be installed and properly torqued.
• Run-out measurements should be taken with all parts installed on the vehicle.

Maximum Run-out Values:

• Disc braking surface (point 1 in Figure 12): Maximum run-out: 0.06 mm (0.002 inches).
• Disc hub (center of the brake disc, point 2 in Figure 12): Maximum run-out: 0.03 mm (0.0012 inches).
• Wheel hub (without the disc installed, point 3 in Figure 12): Maximum run-out: 0.02 mm (0.0008 inches).

Warranty Information

This Technical Service Bulletin (TSB 2022584) is provided for informational purposes only and is not applicable to any Audi warranty. Owners should consult with their dealership regarding specific warranty coverage for any repairs.