Porsche 928 - WORKSHOP MANUAL 1977 Workshop Manual page 123

44
Wheels, Tires, Alignment 928
Further to 4 b: (Fine balancing of the rear wheels)
- Position measuring jack right and left (see mounting points).The driven axle may only be balanced
if both wheels are jacked up simultaneously.
- Set the sensitivity controller to position 3 for Schenck or 3.5 for Hofmann
Make a measurement run at a speed of 130 km/h or 1150 1200 rpm (wheel rotations) with the
Schenck RAW 04, in top gear or in the top driving position.
Fit appropriate balance weights.
Make a check run. If the balance result is not acceptable, calibrate the finish balancer i.e. adapt
the sensitivity controller to the actual conditions.
- Subsequently (with a good balance result) slowly increase the speed to 190 km/h and pay par-
ticular attention to the areas where there are obvious vibrations in the steering wheel and/or in the
seat (predominantly at 175 + 5 km/h).
Maintain this speed and rebalance the wheels as for 130 km/h. Do not fit new weights, but make im-
provements by altering those already fitted according to the "balance correction" schematic.
Note: The imbalance values apparent in this speed range are not 'real" values. Their actual values
amount to mar. l/4 113 of those indicated.
The subjective impression in the vehicle plays an important role. The balancing procedure may only
be terminated when the driver can no longer detect vibrations caused by imbalance.
44- 16
Wheel balancing a
Printed in Germany - XX, 1969