Symptom-based workshop manual

Service
109/21 ENU

4407

4

Noise Symptom – Clicking Noises from the Area of the Front Axle: Observe Specified
Procedure (SY 109/21)
Change overview
Version

Date

Change

0

12/15/2021

•

First publication

1

04/03/2023

•

Dimension in the section "Check rim, brake disc and wheel hub
for geometric discrepancies" adapted from 0.05 mm to 0.1 mm

Model Line:

911 (991)

Model Year:

As of 2014

Equipment:

Central wheel lock (M-no. 478)

Concerns:

Front wheel mounting

Symptom:

The customer complains about clicking noises from the front axle area when turning or turning at slow
speeds.

Cause:

Micro-movements between the contact surfaces of the wheel and brake disc may occur while driving.
These micro-movements can be caused by the following main causes:
•
•
•

Reduced preload on the central wheel lock
Reduced coefficient of friction between the surfaces
Geometric discrepancies

As a result, the rim material is removed from the brake disc.
The transferred material can weld itself to the brake disc and thus cause a stick-slip effect. This
generates the clicking noises during wheel rotation.
Information
The stick-slip effect is the jerking motion that can occur while two solid bodies are sliding over each other.
This phenomenon occurs when a body is moved whose static friction is significantly higher than the
sliding friction.
Remedial
Action:

Check the components of the front wheel mounting as described below and carry out the appropriate
remedial action depending on the respective test result.
When checking the components, ensure that the sequence described below is followed:
•

Check central wheel lock; for instructions, see:  Technical Information 'Check central wheel lock'

AfterSales

Apr 3, 2023
Page 1 of 12

4

Service
ENU 109/21

4407
•
•

Symptom-based workshop manual

Check contact surfaces of rim, brake disc and wheel hub for friction loss, see procedure: 
Technical Information 'Reduced coefficient of friction between the surfaces'
Check rim, brake disc and wheel hub for geometric discrepancies, see procedure:  Technical
Information 'Geometric discrepancies'

Information
The wheel design with central lock was originally developed for race track driving. It allows the wheels to
be changed quickly during a race. Today, the wheel and hub designs with central lock for road vehicles
are significantly different to those of pure racing cars. Given this, the following guidelines and precautionary measures must always be observed when removing or installing the wheels on a road vehicle with
central wheel lock.

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Page 2 of 12

•

The vehicle must be on a lifting platform and the wheels must be hanging freely (no contact with the
floor) while tightening the central lock nut. This ensures that the wheel is centered correctly on the
hub.

•

The parking brake must not be used to counter the rear wheels while tightening. The parking brake
mechanism does not tolerate the high forces while tightening the central wheel lock and can be
damaged. The damage may not be immediately apparent. This applies in particular to the motorized
electronic parking brake actuators.

•

Impact tools must never be used for loosening, removing or tightening the central wheel lock. The
nut and hub can be damaged and the damage may not be immediately apparent.

•

Only a calibrated, high-quality standard torque wrench with sufficient load capacity and levering
effect may be used for tightening the central wheel lock. The use of torque multipliers is not
approved for use on Porsche vehicles.

•

The specified final tightening torque must be reached while turning the torque wrench with a smooth,
continuous motion.

•

The required lubricant must be applied to the contact surfaces of the central wheel lock and rim
in accordance with regulations. For more information, see:  Workshop Manual '440737 Disassembling and assembling central wheel lock'

•

If the central wheel lock, wheel hub or rim is new, the central wheel lock must be tightened to the
specified final tightening torque, loosened and then loosened and tightened again three more times.
This will eliminate any geometrical discrepancies.

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Symptom-based workshop manual

Service
109/21 ENU

4407

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Required parts and materials
Parts Info:

Required parts:
Part No.

Designation
– Point of use

Quantity

WHT008186

 Cheese head bolt, M12 x 1.5 x 62
– Front axle fixed calliper
– PCCB brake system M-no. 450

4 pieces

or
99906704001

Materials:

 Cheese head bolt, M12 x 1.5 x 95
– Front axle fixed calliper
– Grey cast iron brake system

4 pieces

Required materials (usually already available at the Porsche dealer):
Part No.

Designation

Quantity

00004330508

 Mounting paste (100 gram/ 3.52 oz tube)

2 gram/ 0.07 oz

Required tools
Tools:

•
•
•
•
•
•
•
•

Hair ruler, e.g. 12” Starret 380
Feeler gauge, 0.05 mm
Brass brush
Microfiber cloth
– Brake cleaner
9451 - Socket wrench
9794 - Assembly aid
9796 - Socket wrench

Preparatory work
Work Procedure: 1

Remove front wheels.  Workshop Manual '440519 Removing and installing wheel with central bolt'

Check central wheel lock
Information
Reduced preload on the central wheel lock may be due to:
•

Reduced amount of grease on the cone of the central wheel lock or on the thread and external
diameter of the wheel hub

•

A damaged central wheel lock bolt

•

A damaged cone on the rim

AfterSales

Apr 3, 2023
Page 3 of 12

4

Service

Symptom-based workshop manual

ENU 109/21

4407

Information
If one or more of the central bolts is damaged, it must be replaced. Make sure that the central bolt is sufficiently greased. For instructions, see:  Workshop Manual '440737 Disassembling and assembling
central wheel lock'
Work Procedure: 1

2

Disassemble central wheel lock.
For instructions, see:
 Workshop Manual '440737 Disassembling and assembling central wheel lock'
Check central wheel lock for sufficient lubricating film  Lubricating film on central wheel lock ,
cracks, deformation  Example of damage and other damage. Damage can occur at the following
points:
•
•
•
•

Wheel hub thread
Central wheel lock thread
Cone on rim
Cone on central wheel lock

Lubricating film on central wheel lock

Apr 3, 2023
Page 4 of 12

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Symptom-based workshop manual

Service
109/21 ENU

4407

4

Example of damage

Information
If using new parts, the procedure for tightening the wheel as described in the Workshop Manual 
Workshop Manual '440519 Removing and installing wheel with central bolt' must be carried out three
times.
Parts Info:

Required parts if necessary for one side of the vehicle:
Part No.

Designation
– Point of use

Quantity

99136108190

 Wheel bolt
– Central wheel lock

1 piece

or
99970766340

 O-ring
– Central wheel lock

1 piece

or
99136118900

 Washer
– Central wheel lock

AfterSales

1 piece

Apr 3, 2023
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Service

Symptom-based workshop manual