Porsche 996 TT, Repair Manual

Page: 351 / 2099

Mounting the wheel on the
vehicle.
4. Electronic fine balancing (static balancing) of the wheel on the vehicle after stationary balancing.
Required only in exceptional cases.
Further to 1: Mounting 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 destroying all of
the careful work. If the tyre turns by as little as 20 mm with respect to the rim, this can worsen an
optimum balancing result.
Mount tyre on the rim. When doing so, it is expedient and necessary in individual cases to mount the
tyre in a favourable position with respect to the wheel (matching). Controlled or uncontrolled matching.
Uncontrolled matching: Turning 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.
Fill tyres to a pressure of approx 4.0 bar. At the latest when the pressure reaches 4.0 bar, the beads must
pop up out of the deep bed and over the hump of the wheel shoulder in order to avoid fractures of the bead
core. If necessary, interrupt the process and generously coat all necessary surfaces with lubricant (tyre
mounting paste). Then repeat the process.
Check the fit of the tyre on the rim by means of the bead centring
line.
Set the prescribed tyre pressure => Wheel rims and tires.
Further to 2: Stationary balancing with optimisation of the rolling
smoothness
Clamp wheel on stationary balancing machine.
Observe the operating instructions of the balancing machine; occasionally adjust the machine 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 refer to Workshop
Equipment Manual, Chapter 3. This centring 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 tyre was mounted correctly and the
quality of the tyre and rim is good.
einordnung
Balancing/optimising wheels 288