A462350202258412

Technical Service Bulletin
46 Brake pulsation diagnostic guidelines
46 23 50 2022584/12 September 18, 2023. Supersedes Technical Service Bulletin Group 46 number 22-26 dated
January 31, 2022,
for reasons listed below.
Model(s)
Year
All Audi Vehicles 2015 – 2025
VIN Range
Vehicle-Specific Equipment
All
Not Applicable
Condition
REVISION HISTORY
Revision
Date
Purpose
12
-
Revised header (Added model years)
11
01/31/2022
Revised header (Added model year)
10
02/10/2021
Revised header (Added model years)
DO NOT use this TSB if there is another TSB for the 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.
Customer states:
• The steering wheel vibrates or pulsates when the brakes are applied.
Technical Background
Brake-related vibrations and pulsations can have multiple root causes, which include—but are not limited to:
driving style, environmental conditions, and the service history of the vehicle. Additionally, as brake pads and
discs wear, their dampening ability is reduced.
Disc thickness variation (DTV) is a common condition that contributes to brake
pulsation (Figure 1). DTV occurs when the two braking surfaces of the brake
disc are no longer parallel to each other. This condition cannot be accurately
measured with normal workshop tools. The most common conditions that
create DTV include:
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intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.
Technical Service Bulletin
• Corrosion/rust build-up.
• Pad material transfer.
• Prolonged use of a disc with the high run-out condition.
Figure 1. Example of DTV.
Production Solution
Not applicable.
Service
Brake-related vibrations and pulsations can have multiple root causes, which include—but are not limited to:
driving style, environmental conditions, and the service history of the vehicle. Additionally, as brake pads and
discs wear, their dampening ability is reduced.
Disc thickness variation (DTV) is a common condition that contributes to brake
pulsation (Figure 1). DTV occurs when the two braking surfaces of the brake
disc are no longer parallel to each other. This condition cannot be accurately
measured with normal workshop tools. The most common conditions that
create DTV include:
• Corrosion/rust build-up.
• Pad material transfer.
• Prolonged use of a disc with the high run-out condition.
Figure 1. Example of DTV.
Production Solution
Not applicable.
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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.
Technical Service Bulletin
Service
Brake pulsation may be noticeable only with specific vehicle speed, brake pedal pressure, and temperature of the
brake components. In order to accurately diagnose the vehicle, it is critical to test drive the vehicle under the
same conditions as the customers would (e.g., speed, braking pressure, etc.). The following are examples of
other conditions that can cause brake pulsation.
Overheated brake components
Overheated brake components can cause permanent damage to the brake discs and brake pads.
Condition: Brake pad material smeared on the brake disc
(Figure 2). This condition can create DTV.
Common cause: An overly-aggressive driving style, which
results in frequent sharp braking without proper cooling off
periods.
Service: Replace the brake discs and pads.
Figure 2. Deposits on the brake disc.
Condition: Blue-tempered or overheated brake discs (Figure 3).
Common cause: Failed component(s) causing constant brake
application. This can also be caused by an overly-aggressive
driving style, which results in frequent sharp braking without
proper cooling off periods.
Service: Replace the brake disc and pads.
Figure 3. Brake disc with heat marks.
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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.
Technical Service Bulletin
Corrosion/rust build-up
The ability to remove any build-up on a brake disc is impacted by the severity of the build-up. If left unattended,
the build-up can permanently damage brake discs and pads.
Condition: Corrosion/rust build-up on the brake discs
(Figure 4). This condition can create DTV.
Common causes:
• Exposure to road salt during winter months, high
humidity, or moisture.
• Vehicle not being driven for prolonged periods of time.
• A gentle driving style with very light brake application
may not be enough to remove build-up (such as rust or
corrosion) on the brake discs and pads.
Service: With careful consideration of the traffic situation,
perform 2-3 ABS stops from speeds above 50mph. Between Figure 4. Corrosion/rust build-up.
each stop, allow the brake components to cool by driving the
vehicle for more than one minute at speeds greater than
50mph. Do not perform ABS stops if brand new pads and/or
discs are installed. Replace brake disc and pads if the
condition is not eliminated.
Condition: Pad material transfer or corrosion marks from
brake pads on the brake disc, also known as “pad marks”
(Figure 5). This condition can create DTV.
Common cause: These marks can appear if the vehicle has
not been driven for a prolonged period of time or if the
brakes are exposed to high humidity or moisture.
Service: With careful consideration of the traffic situation,
perform 2-3 ABS-stops from speeds above 50mph. Between
each stop, allow the brake components to cool by driving the Figure 5. Pad marks on the brake disc.
vehicle for more than one minute at speeds greater than
50mph. Do not perform ABS stops if brand new pads and/or
discs are installed. Replace brake disc and pads if the
condition is not eliminated.
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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.
Technical Service Bulletin
Condition: Excessive brake disc or wheel hub run-out
(Figure 6). Measure according to the Run-out Measurement
Instructions listed below.
Common causes:
• Over-torqued or improperly-torqued wheels (torque
sticks, impact gun, etc.) can distort the brake disc and
hub, causing a run-out condition. Refer to Elsa for proper
torque values and procedures for the VIN.
• Wheels that are not Audi-approved may not have the
same contact surface on the back of the wheel and may
not have the correct center bore dimension, which can
distort the brake disc and hub, causing a run-out
condition.
• External impact or rust build-up between brake disc
and hub.
Service: Replace brake disc(s) and/or hub(s) if
measurements exceed the maximum value listed in the Runout Measurement Instructions.
Figure
6. True disc rotation (a) and disc lateral run-out
(b).
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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.
Technical Service Bulletin
Condition: Worn brake pads (Figure 7).
Common cause: As brake pads and discs reach their wear
limit, their dampening characteristics are reduced.
Service: Replace worn brake pads and discs.
Figure 7. Worn brake pad.
Other common causes
The following factors can impact the condition of the brake and suspension components, which can lead to
pulsation during braking. Always check the repair history and the overall condition of the vehicle.
Condition: Faulty, damaged, or aftermarket suspension
components (ball joints, links, tie rods, bushing, etc.) can
significantly amplify vibration/pulsation or lead to body
vibrations which only become noticeable when braking (Figure
8 and Figure 9).
Service: Diagnose these components accordingly.
Figure 8. Damaged suspension bushing.
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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.
Technical Service Bulletin
Figure 9. Damaged suspension link.
Condition: Wheel/tire imbalance (Figure 10) or radial run-out
can significantly amplify the vibration/pulsation or lead to body
vibrations which only become noticeable when braking.
Service: Inspect the condition of these components and
diagnose accordingly.
Figure 10. Wheel/ tire imbalance.
Run-out Measurement Instructions
To obtain accurate run-out measurements, the following conditions must apply:
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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.
Technical Service Bulletin
• All surfaces that will be measured must be free of
rust/corrosion build-up or pad material transfer.
• VAS6079/1 (or similar measurement tool) is securely
attached to the vehicle (Figure 11).
• The brake disc is secured to the hub with 5 bolts.
• Axle bolt/nut is installed and properly torqued.
• Run-out measurements should be taken with all parts
installed on the vehicle.
Figure 11. Example of the run-out measurement
tool VAS6079/1 properly secured to a solid
suspension component.
Use the following values to determine the severity of the runout:
Disc braking surface (Figure 12, point 1):
• Disc hub and wheel hub run-out impact this value.
• Maximum run-out: 0.06 mm / 0.002”.
Disc hub (center of the brake disc) (Figure 12, point 2):
• Wheel hub run-out impacts this value.
• Disc hub run-out impacts the disc braking surface run-out.
• Maximum run-out: 0.03 mm / 0.0012”.
Wheel hub (without the disc installed) (Figure 12, point 3):
• This value impacts the disc hub and disc braking surface
run-out. High run-out can distort the brake disc.
• Maximum run-out: 0.02 mm / 0.0008”.
Figure 12. Run-out measurement locations: disc
braking surface (1), disc hub (2), wheel hub (3).
Warranty
This TSB is informational only and not applicable to any Audi Warranty.
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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.
Technical Service Bulletin
Additional Information
All parts and service references provided in this TSB (2022584) are subject to change and/or removal. Always
check with your Parts Department and/or ETKA for the latest information and parts bulletins. Please check the
Repair Manual for fasteners, bolts, nuts, and screws that require replacement during the repair.
©2023 Audi of America, Inc. All rights reserved. The information contained in this document is based on the
latest information available at the time of printing and is subject to the copyright and other intellectual property
rights of Audi of America, Inc., its affiliated companies, and its licensors. All rights are reserved to make changes
at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites without the prior expressed written permission of the
publisher.
© 2023 Audi of America, Inc.
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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.