Optimizing Tire and Wheel to Vehicle

Preliminary
The entire process is subdivided into four operations.
1. Mounting the tire on the rim.
2. Stationary balancing of the wheel (eliminating the static and dynamic imbalance) with optimization of the rolling smoothness.
3. Mounting the wheel on the vehicle.
4. Electronic fine balancing (static balancing) of the wheel on the vehicle (after stationary balancing if necessary/not required in most cases).

Step 1: (Mounting The Tire On The Rim)
- Remove rubber residues and dried-on tire paste from the rim, especially from the rim bead and the hump.
- Examine rim for damage; remove old balancing weights.
- Use the prescribed tire mounting paste so that the tire does not turn on the rim the first time the car is driven, thereby destroying all of the careful work (refer to General Instructions). Service and Repair
If the tire turns by as little as 20 mm with respect to the rim, this can worsen an optimum balancing result.
- Mount tire on the rim.
When doing so, it is expedient (and necessary in individual cases) to mount the tire in a favorable position with respect to the wheel (matching).
Controlled or uncontrolled matching is described in General Instructions. Service and Repair
- Fill tires to a pressure of approx. 3 bar.
At the latest when the pressure reaches 3.75 bar, the tire beads must pop out of the deep bed and over the hump of the rim bead in order to avoid fractures of the bead core.
If necessary, interrupt the process and generously coat all necessary surfaces with lubricant (tire mounting paste) again.
Then repeat the process.
- Check the fit of the tire on the rim by means of the bead centering line.
- Set the prescribed tire pressure. Pressure, Vacuum and Temperature Specifications

Step 2: (Stationary Balancing With Optimization Of The Rolling Smoothness)
- Clamp wheel on stationary balancing machine, observing the following important points:
a) Observe the operating instructions of the balancing machine; occasionally adjust the machine if necessary.
b) The support surfaces of the wheel on the balancing flange (leveling surface) and the centering surface must be clean.
c) Centre (clamp) the wheel from the inside with centering clamping device. This centering clamping device fits on all wheel balancing machines approved by Porsche.
- Check radial and axial runout during the 1st measuring run.
Values less than 1.0 mm (better around 0.5 mm) are desirable.
- Consider the size of the measured balancing weights and their distribution on the inner and outer planes (inner and outer rim flanges) critically.
A uniform distribution with low values (e.g. 25/30 g) means that the tire was mounted correctly and the quality of the tire and rim is good.
A value of 60/60 g (80/80 g in the case of wheels with balancing weights affixed on the inside) should not be exceeded.
A greatly different distribution, e.g. 30/70 g is very unfavorable; this usually indicates incorrect mounting.
Problem wheels of this kind often have pronounced radial and axial runout values.
Remedy by "matching" (use the correct tire mounting paste
a) manual improvement possible
b) with the rolling smoothness optimization programme - significant improvement is possible in almost all cases.
The tire pressure must not be less than 1.5 bar overpressure during balancing.
Permissible residual imbalance less than 3 g, or max. 3 g per plane.

Step 3: (Mounting The Wheel On The Vehicle)





- Fasten wheel on wheel hub according to the specifications.
Up to September 1995:
The wheel securing nut (No. 2) is located opposite the valve (No. 1). As of September 1995:
The wheel securing nut is no longer fitted in relation to a specific position in production.
In After-Sales Service, the wheel mounting procedure used up to September 1995 can be retained.
Irrespective of the position of the wheel securing nut, mark the wheel bolt opposite to the valve, if necessary, before removing the wheel.
This will preserve any optimum balancing result achieved by means of fine balancing (finish balancers), even after the wheel is mounted.
- Slightly tighten the wheel bolts.
When tightening, start at the top and tighten uniformly.
Before the vehicle is lowered onto its wheels, tighten the wheel to: 130 Nm (96 ft lb).
- Tire pressure according to specifications. Pressure, Vacuum and Temperature Specifications

Step 4: (Electronic Fine Balancing)
- For electronic fine balancing of the wheels on the vehicle, refer to the operating instructions from the equipment manufacturer for information about handling the equipment.
- When performing fine balancing on all wheels, start with the front axle.
4a. Fine balancing of the front wheels to correct torsional vibrations of the steering wheel at approx. 120 km/h
4b. Fine balancing of the rear wheels to correct vibration at 180 km/h and speeds greater than 230 km/h.
- The following applies to both the front axle and rear axle:
The measured-value pickups must always stand on a firm surface.
The measuring stand support must be located as close to the wheel as possible.
Doors and lids must be closed and the vehicle must not be touched during the measuring operation.
Ensure that the lifting equipment used (jack, platform lift) does not touch the vehicle.
- Affix balancing weights on the outer plane (uniform procedure/could also be distributed or affixed on the inner plane).
Under no circumstance remove the weights affixed during stationary balancing.
Mark the balancing weight required by electronic fine balancing using a prick punch in order to distinguish it.

Step4a: (Fine Balancing Of The Front Wheels)

NOTE: On vehicles with all wheel drive, all four wheels must be raised and must be able to turn freely.

- Position measuring support or both measuring supports.
Ensure that the take-up fork of the measuring support does not damage any parts.
Before the first measuring run, re-check to ensure that slipping from the measuring support is not possible.

- Centre the sensitivity control. Perform measuring run.
- Affix balancing weight if necessary.
Then perform a check run.
If the result is unacceptable (precondition: the work was performed properly), calibrate the finish balancer.
This means that the sensitivity control must be adapted to the actual situation.
- If the balancing result is still not quite right even after calibration (for example, 5 g), change the balancing weight according to the balance correction table (balance correction schematic) and thereby eliminate the residual imbalance.

Step 4b: (Fine Balancing Of The Rear Wheels)

NOTE: On vehicles with all-wheel drive, all four wheels must be raised and must be able to turn freely.

- Place measuring support on the right and left.
Balance the driven axle only if both wheels are jacked up at the same time.
Ensure that the take-up fork of the measuring support does not damage any parts.
Before the first measuring run, re-check to ensure that slipping from the measuring support is not possible.
- Set the sensitivity control to 3 3.5 (depending on the equipment version).
This corresponds to approx. 1/3 of the max. sensitivity.
- Perform measuring run at a speed of 130 km/h or 1,150 to 1,200 rpm (wheel revolutions) in the highest gear or in the upper transmission range.
Affix the corresponding balancing weight.
- Perform a check run.
Calibrate the finish balancer if the balancing result is unsatisfactory.
This means that the sensitivity control must be adapted to the actual conditions.
- Then (in the case of a good balancing result) slowly increase the speed to 190 km/h and carefully observe at what speed obvious vibration can be felt at the steering wheel and/or seat again (mainly at 175±5 km/h).
- Maintain this speed and re-balance the wheels in the same way as at 130 km/h.
Do not affix any new weights; instead, improve the wheels by changing the existing weights according to the "balance correction" schematic.

IMPORTANT: The imbalance values listed here in this speed range are not "real" values. They are actually max. 1/4 to 1/3 of the indicated values.

- The subjective impression in the vehicle is the decisive criterion here.
- The balancing process is complete only when no more vibrations caused by imbalance are perceptible.