Wheels/Tires - Steering Wheel Shimmy/Vibration
44 Steering wheel shimmy, vibration and/or oscillation
44 13 36
2022563/6
February 18, 2013.
Supersedes Technical Service Bulletin Group 44 number 13-35 dated January 18, 2013 for reasons listed below.
Vehicle Information
Condition
Customer feels vibration from 55 - 80 mph (88 - 128 km/h) in the seat, vehicle floor, footwell, pedals, or steering wheel. This condition does not
result in any handling concerns or loss of vehicle control.
Complaints may occur in one or both of the following circumstances:
^ When driving at highway speeds from 55 - 80 mph (88 - 128 km/h).
^ When applying low brake pedal pressure with minor slow down.
Technical Background
Explanations and definitions:
Radial force variation (RFV)
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The radial force or wheel load is the force with which a tire is compressed (Figure 1, 1).
Tires have softer and stiffer areas along their circumference, which is illustrated using springs (Figure 1, A and B).
Figure 1 shows the same tire at different points of rotation (A and B), as it rolls on level road with constant load (radial force).
If this wheel rolls, with constant wheel load / radial force (Figure 1, arrow) the center of the wheel rises and falls on level road because of the
different spring hardness of the tire by the amount x. The change by the amount x can be felt in the vehicle as vibration or shaking of the steering
wheel. The change of the compression force of the tire is the RFV.
To measure RFV a constant force is applied to a rotating tire using a VAS 6230 / Hunter GSP9700 Road Force Measurement(R) System. This
stimulates the force on the tire from the road surface. The fluctuation of the radial force is independent of the turning direction and is measured as
the difference of maximum and minimal radial force (peak to peak value).
On Audi vehicles the peak to peak value must be 271bs (120N) or less.
First Harmonic
The wheel force fluctuations during the turn of the wheel can be mathematically divided into individual harmonic vibrations. For an objective
assessment of the tire stiffness the first harmonic (the basic vibration) is used. The first harmonic is the share of the radial force fluctuation which
causes the strongest vibrations.
On Audi vehicles the first harmonic must be 18 lbs. (80N) or less.
Production Solution
Not applicable.
Service
A structured procedure is critical.
For all repairs, follow the procedure described below. In the case of a repeat repair with original equipment tires with AO marking on the sidewall,
complete these steps in addition to the procedure described below:
- Open an Audi Technical Assistance Center ticket.
- Ensure that the road force values are printed with the before and after values for each wheel and attached to the repair order.
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3. Complete the Vibration Questionnaire.doc and attach to the TACS ticket.
Procedure
1. Eliminate flat spots
Flat spots are created after the warm tire has cooled down after a stationary period of only a few hours. Flat spots will vary based on the type,
size, and make of the tire. Flat spots falsify the radial force fluctuation and must be driven out before checking balance or road force. A test drive
of at least 12 miles (20 km) at various speed ranges (up to 62 mph /100 km/h) is necessary.
Raise the vehicle on a lift/hoist immediately after the test drive then check balance and road force immediately since flat spots may reappear as
the tires cool down.
See information on flat spots in the Repair Manual under Suspension, Wheels, Steering?Wheel and Tire Guide > 44 Wheels, Tires, Wheel
Alignment > Diagnosis and Testing > Wheel and Tire Vibration > Tire Flat Spots from Standing.
Tip: Flat spots are not a sign of a defect and therefore are not a warrantable condition.
2. Measure and reduce the radial force variation
Before starting work, ensure that flat spots have been eliminated.
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Effects of increased radial forces on the vehicle:
Mounting wheels on the balancer
When tightening the wheel on the balancing machine, make sure the contact surfaces of flange and wheel are clean.
It is mandatory to use the appropriate cantering cone and a five-finger style clamping plate (Figure 2, A) (VAS 6243 or similar) when mounting
wheel on the balancer.
Five-finger style clamp centers the wheel on the balancer the same way the wheel is centered on the vehicle.
It also prevents damaging the wheel by not contacting the face of the wheel (Figure 2, B).
Tip: Do not use Quick Match" mode; this mode does not measure road force. Also turn off Smart Weight" balance feature, which can cause
inaccurate readings.
Tip: Use adequate lubrication to ensure that tires are properly seated when they are installed on the wheel or are moved on a wheel to change
mounting position. Be aware that excessive lubricant can cause a tire to slip on the wheel, which will have an impact on the balance and road
force values.
Optimizing the radial forces using the VAS 6230 / Hunter GSP9700 Road Force Measurement(R) System
- Set the tire pressure of every wheel to 36 PSI (2.5 bar).
- Measure, balance, and, if necessary, match the wheel according to the instructions of the machine. Use 18lbs (80N) or less for the first harmonic
vibration as the maximum.
Tip: The tire that is the source of vibration should be replaced if the first harmonic of the radial force cannot be reduced to 18lbs (80N) or below.
This only applies to tires originally installed at the factory.
- Reinstalling the wheel and tire assemblies
- Install the wheels according to VAS 6230 instructions for lowest vibration. The wheel/tire assembly with the lowest road force values should
be installed closest to the driver.
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^ Lowest road force value - left front
^ Second lowest road force value - right front
^ Third lowest road force value - left rear
^ Highest road force value - right rear
2. Reinstall the wheels according to the instructions in Repair Manual> Running gear > 44 wheels, tires, wheel alignment > Installation of
wheels/tires/tire pressure warning > Instructions on wheel change/installation.
- Adjust tire pressures according to the pressures listed in the owner's manual.
- Drive the vehicle in the speed range where complaints occurred to verify repairs.
Tip: If vibrations persist, open an Audi Technical Assistance Center ticket and include completed questionnaires.
Warranty
All warranty claims submitted for payment must be in accordance with the Audi Warranty Policies and Procedures Manual. Claims are subject to
review or audit by Audi Warranty.
The Audi Tire Assistance Program is not an Audi of America, Inc. factory warranty. Audi of America, Inc. does not warranty tires originally
installed or sold as replacement for use on Audi vehicles. Individual tire manufacturers provide all the underlying tire warranties.
Please refer to Audi Tire Center website for warranty coverage and claim submission details.
Required Parts and Tools
Tools
^ Use VAS 6230 / Hunter GSP9700 Road Force Measurement(R) System to check balance, Road Force values, and to make necessary
adjustments.
^ Use centering hub in conjunction with VAS 6243 model-specific clamping plate (5 finger clamping device) or similar device to ensure proper
mounting of wheel and to prevent damage to wheels.
^ Vetronix MTS 4100 NVH Analyzer is helpful when diagnosing vibration concerns and can help narrow down the list of possible sources of the
vibration.
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Additional Information
More information can be found in the following resources:
^ ElsaWeb: Wheel and Tire Guide > Diagnosis and Testing
^ SSP: Noise, Vibration, and Harshness 961403
The following repair procedure(s) will be necessary to complete this procedure:
^ Chassis > Wheel and Tire Guide > Diagnosis and Testing
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service
manuals for the latest information.
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7.4 Service Mode Setup and Features
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