Balancing/Optimising Wheels

Balancing/optimising wheels
General
Excessive wheel imbalance not only produces vibrations and causes the steering wheel to shake, but also results in increased wear on various parts of the running gear.
Even if the wheels are correctly balanced, excessive geometry errors (radial and axial runout) and misshapen tyres, e.g. accumulation of material at one point in the tyre structure (spring action of tyre changes as the tyre rolls), can cause rolling and steering imbalance.

Note!
^ Achieving a good result requires utmost care, observance of the instructions and procedures, and attempting to eliminate even the very last gram of imbalance.

Recommendations/requirements
^ Wheel suspension elements must be in good technical order.
^ The wheels must be clean with no foreign objects in the tyre.
^ Use a tyre measuring gauge, e.g. measuring gauge 136 to check radial and lateral runout values on wheels without flat spots. Values of less than 1.0 mm are desirable - around 0.5 mm would be better.
^ To limit the number of radial runout errors and to optimise smoothness of rolling, it is a good idea - and even necessary in individual cases - to match the tyre (i.e. to fit it in a favourable position with respect to the wheel). Follow tips and fitting instructions as well as information on tyre mounting paste for tyres.
^ If the rims (wheels without tyres) are perfect but the complete wheels have large axial and radial runout values (due to ply breakage or other damage), it may be necessary to replace the tyre.
^ Balance used wheels only after they have been warmed up by driving, otherwise flat spots will simulate imbalance. Never perform matching in the case of flat spots.
^ Correct tyre pressure is an important prerequisite.
^ Place the balancing weights at the prescribed position.

Balancing/optimising wheels
The entire process is divided into three operations.
1. Fitting the tyre on the rim.
2. Stationary balancing of the wheel (eliminating static and dynamic imbalance) with optimization of rolling smoothness.
3. Fitting the wheel on the vehicle.
^ Electronic fine-balancing (static balancing) of wheel on vehicle (after stationary balancing) is not required (status July 2002).

Further to 1: Fitting the tyre on the rim
- Remove rubber residues and dried-on tyre paste from the rim, especially from the rim bead and the hump.
- Examine rim for damage; remove old balancing weights.
- Use the prescribed tyre mounting paste (only TIP TOP Universal, order no. 593 0601, 3.5 kg bucket, or Contifix) so that the tyre does not turn on the rim the first time the car is driven, thereby counteracting all your careful work. If the tyre turns by as little as 20 mm with respect to the rim, this can worsen an optimum balancing result.
- Fit tyre on the rim. When doing so, it is a good idea - and even necessary in individual cases - to fit the tyre in a favourable position with respect to the wheel (matching). Controlled or uncontrolled matching.

Caution! The high tyre seating pressure required at times (maximum 4 bar! this value must not be exceeded!) may cause injury through possible tyre or wheel damage (in the event that several unfortunate factors should occur simultaneously)!
^ The lyre must therefore be filled in the filling cage!





Tyre filling cage

- Fill tyres to a maximum pressure of 4.0 bar. When the pressure reaches 4.0 bar, at the latest, the tyre beads must pop out of the deep bed and over the hump of the rim shoulder in order to avoid fractures of the bead core. If necessary, interrupt the process and coat all necessary surfaces generously with lubricant (tyre mounting paste). Then repeat the process.
- Uncontrolled matching: Turn the tyre on the wheel by 90° or 180° if necessary in order to achieve an acceptable value with regard to rolling smoothness (true running, imbalance and distribution of balance weights).
- Controlled matching: With a balancing machine with matching program. In most cases, this produces an even better result with regard to the rolling smoothness (true running, imbalance and distribution of the balance weights) than can be achieved with uncontrolled matching.
- Check the fit of the tyre on the rim using the bead centring line.
- Set the prescribed tyre pressure.

Further to 2: Stationary balancing with optimization of rolling smoothness
- Clamp wheel on stationary balancing machine.
- Observe the operating instructions of the balancing machine; adjust the machine from time to time, if necessary.
- The support surfaces of the wheel on the balancing flange (levelling surface) and the centring surface must be clean.
- Centre (clamp) the wheel from the inside with centring clamping device-. This centring clamping device fits on all wheel-balancing machines approved by Porsche.

Check radial and axial runout during the first measuring run. Values of less than 1.0 mm are desirable - around 0.5 mm would be better.
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. 35/40 g) means that the tyre was fitted correctly and the quality of the tyre and rim is good.
A value of 110 grams/110 grams (120 grams/120 grams using the tyre pressure monitoring system) should not be exceeded with interior balancing behind wheel centre. A considerably different distribution, e.g. 40/90 g is very unfavourable; this usually indicates incorrect fitting. Problem wheels of this kind often have pronounced radial and axial runout values.
This can be remedied by matching (use correct mounting paste). This can be improved with uncontrolled matching (manual); significant improvement is possible in almost all cases using the rolling smoothness optimization program (controlled matching).
Tyre pressure during balancing with required pressure.
Permissible residual imbalance of less than 3 grams, or maximum 3 grams per plane.

Further to 3: Fitting the wheel on the vehicle

Note!
^ Never use an impact bolter!
^ Observe information on the two-piece wheel bolt! This is described in the section describing wheel removal and installation (fitting wheel on the vehicle)!

- Fit wheel using a suitable commercially available tool.
- Screw in wheel bolts by hand and then tighten evenly. Start at the top when tightening. Always observe the specified tightening torque of 160 Nm (11 8 ft. lbs.).
- Tyre pressure.

Balancing weights
Balancing weights: Adhesive weights as used previously (no special version necessary).





Attach both weights to the inner side.

Note!
^ Observe program selection and operating instructions of the balancing machine.

Attaching the adhesive weights

Note!
^ Only remove the protective film immediately before sticking on the weight as prolonged exposure to the air will reduce the bonding strength!
^ Pay attention to cleanliness!

- Determine exact position of the balancing weights (if necessary, provisionally stick on the balancing weights with a strip of adhesive tape until the correct position is determined).
- Prepare bonding surface on the rim. The bonding surface must be perfectly clean and free of grease.
- Remove protective paper from the bonding surface of the weight and press the weight firmly into place.
- The adhesive weight must be in contact uniformly over the entire surface.
- Check to ensure that the balancing weight is seated firmly. It must not be possible to detach the weight that was just stuck onto the rim by applying a shear load at right angles to the longitudinal axis of the weight.