Alignment: Service and Repair
WM 449503 Suspension alignment, complete
Tools
Information
General procedure for wheel alignment
Perform wheel alignment using an electronic wheel alignment tester. Measurement procedures should be taken from the operating instructions for the wheel alignment tester.
In order to exclude erroneous measurements, the following preconditions must be met before alignment and the following points should be given special attention:
- Unladen weight of vehicle according to DIN 70020, i.e. vehicle in ready-to-drive condition with full tank and including tools but without driver or additional weights.
- Ball-joint and wheel-bearing play in order (wheel-bearing play cannot be adjusted).
- Tyre pressure in accordance with regulations, fairly uniform tyre tread.
- Use self-centring quick-clamping holders Porsche Quick-Clamping Unit WE 1265 to secure the measured-value pickups to the wheels. The self-centring quick-clamping holders are positioned centrally (with the claws first) in the centre of the rim and are tautened in the rim by turning the straining ring (clockwise).
- Receiving surfaces for the quick-clamping holder on the wheels and the adapter surfaces must be clean and flat. In particular, always accurately check the levelling surface on the wheels before fitting the quick-clamping holders. Quick-clamping holder with adapter (for the measured-value pickups) correctly secured to the wheels.
Self-centring quick-clamping holder
- Strictly comply with maintenance intervals for measuring equipment and measuring platform. If the levelling of the measuring platform or of the measuring area is done in-house, levelling equipment is required. A spirit level is not adequate. The permissible level tolerances are: transverse front axle: max. 1.0 mm/transverse rear axle: max. 1.0 mm/longitudinal: max. 1.0 mm/diagonal: max. 1.5 mm.
- The measuring equipment and measuring platform must be handled competently.
- Sliding plates with transverse motion (rotary motion) at the rear axle are advisable.
- Observe the Technical Literature of PAG, the manufacturer of the measuring equipment and the manufacturer of the measuring platform.
- Do not treat measured values as a whole, but very critically with regard to driving dynamics, tyre wear and cost/benefit effects (time required for correction of insubstantial deviations). The toe values are of decisive significance for driving dynamics and tyre wear.
- If the vehicle is measured front and rear, check and adjust the wheel alignment values at the rear axle first. The camber values at the front axle are valid if the wheels are in the straight-ahead position. The steering wheel and steering gear should be centred when adjusting the toe.
- Before wheel alignment values are adjusted at the front and rear axles, it is recommended that the vehicle height be checked at the DIN empty weight. Conclusions can then be drawn about wheel alignment values in the event of any suspension alignment that becomes necessary later.
- Calibrate the steering-angle sensor if the previous wheel alignment values (at rear and/or front axle) were changed. In each individual case (if the wheel alignment values where changed only slightly), read out the steering-angle sensor actual value first and only calibrate the steering-angle sensor if necessary.
Aligning vehicle at front and rear
Vehicle height (height check)
The vehicle height at front and rear axle is not adjustable.
For the height check, place the vehicle on a level surface or on the measuring platform (ready to drive, with a full tank and tools but without driver or additional weights). Compress (push down) vehicle at front and rear axles 2-3 times and allow it to spring back freely.
Front axle
- Measure from road contact surface to hexagon-head bolt on cross-member threaded connection to the body.
Measuring height of front axle (left-hand side)
Nominal value for front and rear axles -> 4400TW Adjustment values for suspension alignment.
Rear axle
- Measure from wheel contact area up to lower edge of diagonal brace (at control arm fastening point).
Measuring the height of the rear axle (right-hand side)
Wheel alignment
WARNING
Steering-angle sensor not calibrated or calibrated incorrectly
- Unexpected vehicle handling
- Steering-angle sensor does not function
- Malfunction in steering-angle sensor
-> After working on wheel suspension parts, when replacing the steering-angle sensor and after changing the wheel alignment values, calibrate the steering-angle sensor using PIWIS Tester II 9818.
-> Keep the front wheels in straight-ahead position on the measuring platform during calibration.
-> Check the actual value of the steering-angle sensor after suspension alignment where no changes were made to the wheel alignment values.
1. Prepare vehicle for checking and/or adjustment of wheel alignment values.
2. Place front wheels on rotary table and rear wheels on rotary/sliding plates.
3. Compress vehicle at front and rear axles by approximately 25 mm 2-3 times and allow it to spring back freely.
Rear axle
When adjusting the camber or toe, there is mutual influence (if the camber value is changed, the toe value also changes). You should therefore adjust the camber and toe (gradually) at the same time.
Adjusting rear axle camber
Information
- Due to the restricted space, to tighten the lock nut of the left camber eccentric, use a 3/8 inch torque wrench (covering the range of 100 Nm (74 ftlb.)) together with a 18 mm socket-wrench insert.
- 3/8 inch torque wrenches and 3/8 inch socket-wrench inserts have a smaller height than tools of the same size in a 1/2 inch version.
After loosening the lock nut, turn the eccentric -B- as required. After adjusting, tighten the lock nut of the eccentric to the prescribed tightening torque.
-> 420000 Tightening torque for rear axle.
Toe and camber eccentrics
Adjusting rear axle toe
After loosening the lock nut, turn the eccentric -A- as required. After adjusting, tighten the lock nut of the eccentric to the prescribed tightening torque.
-> 420000 Tightening torque for rear axle.
Toe and camber eccentrics
Front axle
Adjusting front axle camber
The camber is adjusted by moving the spring strut transversely.
- Loosen three fastening nuts -Arrows- on the spring strut mount. Move the spring strut transversely until the desired nominal value is reached. To move the spring strut, remove the cap on the piston rod.
Tighten fastening nuts to the prescribed tightening torque.
-> 4001TW Tightening torques for front axle 4001TW Tightening torques for front axle
Adjusting camber
Caster
The caster cannot be adjusted on standard vehicles.
Adjusting front axle toe
Adjust front axle toe with steering gear centred.
Due to the variable steering transmission ratio and therefore the fact that the steering angle is the same on the right and left, the exact centre position must be ensured.
1. First check whether the steering wheel is displaced with respect to the steering gear when the steering is centred -Arrow-. If the steering wheel is displaced by more than half a tooth (more than 2.5 degrees) with respect to the centre steering position -Arrow- , reposition the steering wheel accordingly.
Mark for the centre steering position
Moving the steering wheel by one tooth on the steering shaft corresponding to a change in angle of approx. 4.2 degrees.
Centre the steering gear as described below:
1.1. Turn wheels to the straight-ahead position.
1.2. Then readjust the front wheel alignment, if necessary, until the pin -2- in the driver -1- and the lug on the steering gear housing -4- line up. This is the centre steering gear position.
Steering in centre position
-3- is the desired breaking point for pins in new steering gears. The (new) pin -2- is inserted into the driver -1- and its underside sits in the lug -4-. This locks the steering gear in the centre position. After installation of a new steering gear, the lower part of the pin is sheared off (at the desired breaking point -3- ) by turning the steering wheel. The upper part of the pin -2- remains in the driver -1-.
1.3. If the steering wheel (when the steering gear is in the centre position) is not centred and is displaced by more than one half tooth, reposition it accordingly. When doing this, try to find the best position.
Moving the steering wheel by one tooth on the steering shaft corresponding to a change in angle of approx. 4.2 degrees.
WARNING
Unsuitable steering-wheel holder used
- Triggering of airbag unit
-> Use only steering wheel holders that do not project into the area of the airbag unit during suspension alignment work.
-> Observe the safety regulations for handling airbag units.
2. Clamp the steering wheel in the centre position with the steering wheel holder -A-. Use only steering wheel holders that do not project into the area of the airbag unit -B-. If necessary, shorten the guide rod of the steering-wheel holder at the top -Arrow-.
For fast and reliable steering wheel alignment in the centre position use a -Lenkradwaage (Beispiel)- , with integrated angle measurement box.
=> WE1343 steering wheel balance.
Steering wheel holder
Steering wheel balance (example)
3. Adjust the toe of the corresponding tie rod or at both tie rods (depending on the actual value).
3.1. Loosen the tie rod lock nut(s) -2- at the corresponding tie rod or at both tie rods. Apply counter-pressure with a spanner when loosening or tightening tie rod lock nuts on the square part of the tie rod -3-.
Next, adjust the toe at the hexagonal part -1- of the tie rod(s). Then tighten the tie rod lock nut(s) -2- to the specified tightening torque.
Adjusting toe
To loosen and tighten the tie-rod lock nut(s), use special tool (socket-wrench insert) P 9730 -A- together with a torque wrench -B-. The tightening torque for the tie rod lock nut(s) of 50 Nm (37 ftlb.), when using a socket-wrench insert 9730, corresponds to a value of approx. 32.5 Nm (24 ftlb.) on the torque wrench.
Loosening and tightening the tie rod-lock nut
Toe-difference angle
The toe difference angle cannot be adjusted.
The toe-difference angle value is also influenced by the vehicle height. For this reason the measured result must be evaluated accordingly. No action is necessary in the case of small deviations from the toe-difference angle's required value as long as the value to the right and left is almost the same.
Calibrating steering-angle sensor
WARNING
Steering-angle sensor not calibrated or calibrated incorrectly
- Unexpected vehicle handling
- Steering-angle sensor does not function
- Malfunction in steering-angle sensor
-> After working on wheel suspension parts, when replacing the steering-angle sensor and after changing the wheel alignment values, calibrate the steering-angle sensor using PIWIS Tester II 9818.
-> Keep the front wheels in straight-ahead position on the measuring platform during calibration.
-> Check the actual value of the steering-angle sensor after suspension alignment where no changes were made to the wheel alignment values.
- Calibrate the steering-angle sensor if the previous wheel alignment values (at rear and/or front axle) were changed. If each individual case (if the wheel alignment values where changed only slightly), read out the steering-angle sensor actual value first and only calibrate the steering-angle sensor if necessary.
-> 456015 Initialise and calibrate steering-angle sensor Testing and Inspection.