Procedure for optimizing the wheels

The complete procedure is subdivided into 4 working steps

1. Fitting the tire to the rim

2. Stationary balancing of the wheel (eliminating static and dynamic imbalance) with optimization of smooth running

3. Fitting the wheel to the vehicle

4. Electronic fine balancing (static balancing) of the wheel on the vehicle (after stationary balancing if required - not usually necessary)

Further to 1: (Fitting the tire to the rim)

- Clean the rim; above all, remove residua! rubber and dried-on tire paste from the bead seat and the hump.

- Inspect the rim for damage, remove old balance weights.

- Use specified tire assembly compound (refer to page 44 - 7) to keep the tire from rotating on the wheel during the first drive as this would render all the careful work useless (20 mm tire slip on the wheel may be enough to reduce good balancing results to average results only).

- Mount the tire on the rim, aligning matching points (if available) of tire and rim. Bear in mind that it is possible to achieve an even better result in some cases from the point of smooth running and imbalance using a wheel-balancing machine with matching program (see Page 44 - 8).

- Inflate tires to approx. 4 bar; the beads should slip over the rim shoulder hump at a pressure of 3.3 bar* at the latest.

- Check that the tire is seated correctly on the rim by means of the bead centering line.

* 4.5 bar max. for wheels with asymmetrical hump (p. 44 - 18a).

Further to 2: (Stationary balancing with optimization of smooth running)

- Clamp the wheel onto a stationary balancing machine, observing the following under all circumstances:

a) Follow the operating instructions of the respective balancing machine, adjust the machine from time to time if necessary.

b) The contact surface of the wheel at the bead flange (level surface) and the middle centering device must be clean.

c) Center from the inside outwards using a stepped ring (cylindrical ring - commercially available Porsche version, e.g. from Messrs. Schenck or Messrs. Hofmann).

Do not center from the outside as well d) Clamp the wheel onto the balancing machine as specified (valve always pointing upwards, the wheel will then drop downwards through the small amount of play necessary when centering, before tightening) and then fit to the vehicle in the same position (there may otherwise be a shift of up to 1/2 oz).

In the case of balancing machines with horizontal wheel fixture (wheel lying), position the valve opposite the mechanic, then pull the wheel in this position in the direction of the mechanic and clamp firmly.

- Check the radial and lateral run-out during the first measurement procedure. Try to achieve values less than 1.0 mm and greater than 0.5 mm.

- Be critical with regard to the size of the measured balance weights and their distribution on the inner and outer rim flange.

Even distribution with low values (e.g. 3/4 / 7/8 oz) indicates that the tires are correctly fitted and that the quality of tires and rims are in good order.

Do not exceed a value of 1 3/4/1 3/4 oz, a widely deviating distribution, e.g. 1 / 2 1/2 oz is very unfavorable, this usually indicates a fitting fault. Problem wheels of this sort often have obvious radial and lateral run-out.

- Remedy by "matching' (use the correct fitting paste sparingly / Page 44 - 7/8)

a) Manual improvements are possible b) Considerable improvements possible in virtually all cases with smooth- running optimization program.

- When balancing, the tire pressure should not be less than 22 psi.

- Permissible residual imbalance less than / or max, 1/10 oz per side.

Further to 3: (Fitting the wheel to the vehicle)

- Fasten the wheel to the wheei hub as prescribed (also see Page 44 - 9 - General assembly instructions, tires). Always fit the best wheels on the left.

- Valve must point up or, for 17-inch Cup Design wheels, down (same position as on the balancing equipment). Observe instructions on page 44 - 03.

- Bore close to valve is for wheel mounting; fit lockable wheel nut to color-coded wheel stud. On 17-inch wheels, locate the valve opposite the marked stud. Tighten nuts, start tightening equally at the top. Before lowering the vehicle onto its wheels, tighten wheels to 130 Nm (96 fltb.) to make sure that its predefined position on the wheel hub does not change anymore.

- Tire pressure according to specification

Further to 4: (Electronic fine balancing)

- Use the RAW 04 from Messrs. Schenck ASG or ipk 2 from Messrs. Hofmann for electronic fine balancing of the wheels on the vehicle. Refer to the equipment's operating instructions for procedure.

- If all wheels are to be finely balanced, begin at the front axle.

4a Fine balancing of the front wheels because of steering-wheel vibrations at approx. 120 km/h 4b Fine balancing of the rear wheels because of vibrations at 180 km/h and greater 230 km/h

• The following generally applies for front and rear axles: the measurement jacks must stand on a firm foundation, must only record at the specified points (measurement fixture situated as close to the wheel as possible), doors and hoods must be closed and the vehicle must not be touched during the measurement run. Ensure that the lifting equipment (Jack, platform) has no contact with the vehicle.

- Attach balance weights to the outside (uniform procedure / may also be distributed - or fitted to the inside).

Under no circumstances remove the weights fitted during stationary balancing.

Identify balance weights from electrical fine balancing with a center punch.

88/266

10778 A

0 0

Post a comment