4

Bulletin #: 2106

Advanced Technical Information

Part ID: 4405

991 – Clicking Noises from Centerlock Wheels
Vehicles Affected
Models

Model Year

Model Type

VIN Range

Vehicle-Specific Equipment

911 Carrera GTS, Turbo, Turbo S,
GT3, GT3RS, GT2RS, Speedster

As of 2014
up to 2019

991

N/A

Centerlock wheel nuts, aluminum
alloy wheels, and PCCB brake discs

Revision History
Revision

Release Date

Changes

0

April 9, 2021

Original document

Condition
The customer complains of clicking noises from the front of the vehicle
while turning, typically at slow speeds.

Figure 1
Clicking Noise Example (Sound File)
In order to play this sound file, you need to enable “playing of 3D content”
under 3D & Multimedia in the preference settings (Edit) of Adobe Acrobat.

Technical Background
The wheels may experience “micro-movements” at the interface with the brake disc bell during driving. Micromovements may be caused by an insufficient pretension of the centerlock nut, reduced friction values between
multiple contact surfaces, or geometrical discrepancies between parts.
These micro-movements may cause material to be transferred from the aluminum alloy wheels to the brake disc
bell. The transferred material may cold-weld to the brake disc bell, causing a “stick-slip” effect. The stick-slip effect
produces clicking noises while turning.

AfterSales

April 9, 2021
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Bulletin #: 2106

Advanced Technical Information

Part ID: 4405

4

Service Information
To eliminate the clicking noises, please perform the following:
1.
2.

Remove both front wheels and both front brake discs.
Visually inspect for damage on the brake discs, wheel hubs, wheel cones (seat on the wheel for the center
lock nuts), centerlock nut assemblies, wheels, and drive pegs. Replace any damaged parts and document all
damage with pictures.

3.
Inspect the outer surface of the brake disc bell and the inner surface of the wheel that contacts the brake

disc bell. If any material transfer or corrosion is present on either surface (Figure 2), gently and thoroughly

clean the surface of both parts. Document any material transfer and corrosion with pictures.

a.
To clean the surfaces, please use special tool VAS 294009 – Wheel Hub Cleaner.
i.
Only if special tool VAS 294009 is unavailable, 3M Scotch-Brite Hand Pads 7445 (white)

and 7448 (light gray) may also be used.

1.
Begin by gently cleaning with pad 7445. If pad 7445 does not completely remove

all corrosion and material transfer from the surfaces, gently clean the surfaces with
pad 7448.
2.
Note: Do not use a more abrasive Scotch-Brite pad than pad 7448. Doing so may

remove any protective coating from the surfaces of the wheel and brake disc bell.

Figure 2
Material Transfer to Brake Disc Bell (Left) from Wheel (Right)

b.
If a surface cannot successfully be cleaned, replace only the component that cannot be cleaned.

i.
If no parts are replaced, or if only the wheel is replaced, or if only the brake disc is replaced,
continue to Step 4.

ii.
If both the wheel and brake disc are replaced, skip to Step 6.

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Bulletin #: 2106

Advanced Technical Information

Part ID: 4405

4.

Inspect for material transfer on the contact surfaces between
the drive pegs and brake disc (Figure 3).
Replace the drive pegs and all drive peg screws if material
transfer is present. Document any material transfer with pictures.

5.

Check the flatness of the inner wheel surfaces per ATI 4 1503 Clicking Noise From Front PCCB Rotors.
Document any unevenness with pictures.

4

Figure 3
Material Transfer on Drive Peg

6.
If any anti-corrosion oil is present from manufacturing on any

mating surfaces (marked in red with white arrows in Figure 4),

on new or old parts, clean the parts with a microfiber cloth and

brake parts cleaner. Document presence of anti-corrosion oil
with pictures.

Figure 4
Mating Surfaces to Check for
Anti-Corrosion Oil

7.

Thoroughly clean the centerlock nut and apply a complete layer of
Optimoly grease to the centerlock cone.

Figure 5
Application of Grease to
Centerlock Cone

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8.

4

Bulletin #: 2106

Advanced Technical Information

Part ID: 4405

Thoroughly clean the wheel hub threads and apply a complete
layer of Optimoly grease to both the inside threads and the
outside diameter.

Figure 6
Application of Grease
to Wheel Hub

9.

If the wheel hubs were replaced, reinstall the wheel hubs and bearings as instructed in
WM 405719 – Removing and installing front wheel bearing, section on Installing front wheel
bearing. If wheel hubs were not replaced, skip to Step 10.
a.
Note: If the wheel bearings are damaged during the removal of the wheel hub, the parts
must be replaced.

10.

Reinstall the PCCB brake discs as instructed in WM 465119 – Removing and installing front PCCB
brake disc, section on Installing front brake disc.

11.

Reinstall both wheels as instructed in WM 440519 – Removing
and installing wheel with central bolt, section on Installing wheel
with central bolt.
a.
Please use recomended special tool QD4RN800A – Torque
Wrench from Snap-on for the centerlock wheels.
Note: When tightening the centerlock nuts, ensure that
the nuts are tightened in one continuous motion. This
guarantees that the prescribed tightening torque is
achieved. Please see sections 6.1-6.3, within section on
Installing wheel with central bolt, for proper tightening
procedure and tightening torque values.

Figure 7
Proper Centerlock Tightening Motion (Video
File)
In order to play this video, you need to enable “playing of 3D
content” under 3D & Multimedia in the preference settings (Edit)
of Adobe Acrobat.

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4

Bulletin #: 2106

Advanced Technical Information

Part ID: 4405

Warranty
As always, be sure to document the repair completely in PQIS. All pictures taken during the repair procedure should
be attached to the PQIS job.
For this repair, please code the “cause” as follows:
Cause location:
4407A
Central bolt for wheel mounting
Cause symptom:
2015
Clicks
Always use the following troubleshooting labor operations:
44052011 2
Wheels remove and reinstall
44073761
Wheel mounting disassemble and assemble
44073762
Wheel mounting disassemble and assemble
44120200 2
Rims check
46510250 2
Front PCCB brake discs check
46512050 2
Front PCCB brake discs remove and reinstall
The following troubleshooting labor operations are conditional and should only be used as necessary:
44125501
Rim replace (if only front left replaced)
44125502
Rim replace (if only front right replaced)
44125600
2 Rims replace (if both replaced)
40641955
Front wheel hub remove and reinstall (only if front left replaced)
•
Also claim 40501905 Wheel bearing housing remove and reinstall from “Preconditions” list
40641956
Front wheel hub remove and reinstall (only if front right replaced)
•
Also claim 40501906 Wheel bearing housing remove and reinstall from “Preconditions” list
40642055
2 Front wheel hubs remove and reinstall (only if both replaced)
•
Also claim 40502005 2 Wheel housing bearings remove and reinstall from “Preconditions” list
Search Items
Wheel clicking, centerlock clicking, 991 wheel clicking, 991, GT3, GT3RS, GT2RS, 911 Turbo, 911 Turbo S

Important Notice: Technical Bulletins issued by Porsche Cars North America, Inc. are intended only for use by professional automotive technicians who have attended Porsche service training courses. They are
written to inform those technicians of conditions that may occur on some Porsche vehicles, or to provide information that could assist in the proper servicing of a vehicle. Porsche special tools may be necessary in
order to perform certain operations identified in these bulletins. Use of tools and procedures other than those Porsche recommends in these bulletins may be detrimental to the safe operation of your vehicle, and
may endanger the people working on it. Properly trained Porsche technicians have the equipment, tools, safety instructions, and know-how to do the job properly and safely. Part numbers listed in these bulletins
are for reference only. The work procedures updated electronically in the Porsche PIWIS diagnostic and testing device take precedence and, in the event of a discrepancy, the work procedures in the PIWIS Tester
are the ones that must be followed.

F12993
©2021 Porsche Cars North America, Inc.

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