2021-2026 Audi Brake Pulsation Diagnostic Guidelines TSB

Experiencing a vibrating or pulsating steering wheel when you brake can be unsettling and indicates a potential issue with your vehicle's braking system. Audi has released Technical Service Bulletin (TSB) 2022584/12 to help technicians diagnose and address these concerns in 2021-2026 Audi vehicles. This bulletin, dated September 18, 2023, supersedes an earlier version, TSB Group 46 number 22-26 dated January 31, 2022, and offers detailed guidance on identifying the root causes of brake pulsation.

This TSB is primarily for diagnostic purposes and helps identify why your 2021 Audi e-tron brake pulsation is occurring.

Important Notice for Technicians

Audi advises that this TSB should NOT be used if another TSB for the same concern is applicable to the vehicle's VIN. It is intended solely for diagnostic purposes and does not serve as a guideline for determining warrantable conditions.

Symptoms of Audi Brake Pulsation

Owners typically report the following symptom:

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

This sensation often varies with vehicle speed, brake pedal pressure, and the temperature of the brake components. Accurate diagnosis often requires a test drive under conditions similar to those experienced by the customer.

Technical Background: Understanding Brake Pulsation

Brake-related vibrations and pulsations can stem from multiple factors, including driving style, environmental conditions, and the vehicle's service history. Over time, as brake pads and discs wear, their ability to dampen vibrations 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 with standard workshop tools. Common conditions that lead to DTV include:

• Corrosion/rust build-up on the brake disc surfaces.
• Transfer of pad material onto the brake disc.
• Prolonged use of a brake disc that already has a high run-out condition.

Common Causes and Solutions for 2021-2026 Audi Brake Pulsation

The TSB outlines several specific conditions that can cause brake pulsation and provides recommended service actions.

Overheated Brake Components

Overheating can permanently damage brake discs and pads.

• Condition: Brake pad material smeared on the brake disc or blue-tempered/overheated brake discs.
• Common Cause: An overly aggressive driving style involving frequent sharp braking without adequate cooling periods, or failed components causing constant brake application.
• Service: Replace the affected brake discs and pads.

Corrosion/Rust Build-up

Build-up on brake discs can lead to permanent damage if left unaddressed.

• Condition: Corrosion/rust build-up on the brake discs.
• Common Causes: Exposure to road salt during winter months, high humidity, moisture, prolonged periods of the vehicle not being driven, or a gentle driving style that doesn't adequately remove build-up.
• Service: With careful consideration for traffic, perform 2-3 ABS stops from speeds above 50 mph. Between each stop, allow brake components to cool by driving for over one minute at speeds greater than 50 mph. Do NOT perform ABS stops if brand new pads and/or discs are installed. If the condition is not eliminated, replace the brake disc and pads.

Pad Material Transfer

Also known as "pad marks," this condition can also create DTV.

• Condition: Pad material transfer or corrosion marks from brake pads on the brake disc.
• Common Cause: Vehicle not driven for a prolonged period, or brakes exposed to high humidity/moisture.
• Service: Similar to corrosion, perform 2-3 ABS stops from speeds above 50 mph, allowing cooling time between stops. Do NOT perform ABS stops if brand new pads and/or discs are installed. If the condition persists, replace the brake disc and pads.

Excessive Brake Disc or Wheel Hub Run-out

Run-out refers to deviations from a perfect circle or plane. Excessive run-out can distort the brake disc and hub, causing pulsation.

• Condition: Excessive brake disc or wheel hub run-out.
• Common Causes:
  • Over-torqued or improperly-torqued wheels: Using impact guns or incorrect torque values can distort the brake disc and hub. Refer to Elsa for proper torque values and procedures for the VIN.
  • Non-Audi-approved wheels: Wheels that lack the correct contact surface or center bore dimension can distort the brake disc and hub.
  • External impact or rust build-up: Between the brake disc and hub.
• Service: Replace brake disc(s) and/or hub(s) if measurements exceed the maximum values specified in the Run-out Measurement Instructions.

Worn Brake Pads

As brake pads wear down, their dampening capabilities diminish.

• Condition: Worn brake pads.
• Common Cause: Normal wear and tear.
• Service: Replace worn brake pads and discs.

Other Suspension or Wheel Issues

Various other components can contribute to or amplify vibrations.

• Condition: Faulty, damaged, or aftermarket suspension components (e.g., ball joints, links, tie rods, bushings) or wheel/tire imbalance/radial run-out.
• Service: Inspect and diagnose these components accordingly.

Run-out Measurement Instructions

To obtain accurate run-out measurements, technicians must adhere to specific conditions:

• All surfaces to be measured must be free of rust/corrosion build-up or pad material transfer.
• The special measurement tool, VAS6079/1, or a similar device, must be securely attached to the vehicle.
• The brake disc must be secured to the hub with 5 bolts.
• The axle bolt/nut must be installed and properly torqued.
• Run-out measurements should be taken with all parts installed on the vehicle.

The TSB provides maximum allowable run-out values:

• Disc braking surface: Maximum run-out: 0.06 mm (0.002 inches). This value is affected by disc hub and wheel hub run-out.
• Disc hub (center of the brake disc): Maximum run-out: 0.03 mm (0.0012 inches). This value is affected by wheel hub run-out.
• Wheel hub (without the disc installed): Maximum run-out: 0.02 mm (0.0008 inches). High run-out here can distort the brake disc.

Warranty Information

This Technical Service Bulletin (TSB 2022584/12) is informational only and is not applicable to any Audi Warranty.

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NHTSA ID: 10242946