Suspension Alignment, Complete
Suspension alignment, complete
Tools
Important notes
Suspension alignment on the new 911 Carrera (996) differs in a number of respects from that of the previous 911 Carrera suspension alignment procedures. This involves the vehicle height adjustment, the wheel-load difference from left to right, special tools and corrections to wheel alignment.
Vehicle height/wheel load
There is no facility for adjusting the vehicle height. This applies to both the front and the rear axles.
The varying thickness of pads between coil springs and spring seats on the right and left spring struts on the front and rear axles is not intended for changing the vehicle height but for compensating for differences in coil-spring load groups.
Since the vehicle height can no longer be adjusted, there is no need for adjustment (fine adjustment) of the wheel-load difference between left and right at the front and rear axles. Because of the different equipment versions (additional equipment), a greater wheel-load difference between the left and right is permissible than previously was the case in Porsche suspension alignment (over 20 kg is possible; maximum was previously 20 kg).
This is partly the result of heavier components compared with standard equipment and partly results from additional components that are asymmetrically arranged.
Wheel-alignment corrections
Rear axle: The kinematic toe-in is not adjustable. Camber and toe can be adjusted via eccentrics.
Front axle: The caster is not adjustable on standard vehicles. In the event of repairs, a caster adjustment facility can be installed if necessary (as with the Boxster).
The camber is adjusted by moving the spring strut transversely. For this purpose, loosen the three fastening nuts of the spring-strut mount.
After adjusting the toe, the lock nuts on the track rods must be tightened to the prescribed tightening torque of 50 Nm (37 ft. lbs.).
The steering angle sensor must be calibrated if the previous wheel alignment values for vehicles with PSM (Porsche Stability Management) were changed! The steering angle sensor actual value must be checked after a suspension alignment which resulted in no changes being made to the wheel alignment values.
The Porsche System Tester 2 is necessary to calibrate the steering angle sensor and to check the steering angle sensor actual value.
General procedure for wheel alignment
Carry out suspension alignment with an optical or electronic wheel alignment tester. The measurement procedures should be taken from the operating instructions for the wheel alignment tester involved.
In order to exclude erroneous measurements, the following preconditions must be met before alignment and the following points should be given special attention:
Empty weight of vehicle in accordance with DIN 70020, i.e. car ready for the road, with full fuel tank, spare wheel and tools.
Ball-joint and wheel-bearing play in order (wheel-bearing play cannot be adjusted).
Tyre pressure in accordance with regulations, fairly uniform tire tread.
Quick-clamping holder with adapter (for the measured-value pickups) correctly secured to the wheels.
Receiving surfaces for the quick-clamping holder on the wheels and the adapter surfaces must be clean and flat. Always check the leveling surface on the wheels precisely in particular before fitting the quick-clamping holders.
Strictly comply with maintenance intervals for measuring equipment and measuring platform. If the leveling of the measuring platform or of the measuring area is done in-house, leveling equipment is required. A hose level is inadequate.
Skilled handling of measuring equipment and measuring platform.
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 in regard to driving dynamics, high-speed strength of the tyres, tire wear and cost/benefit effects (time required for correction of insubstantial deviations). The toe values are of decisive significance for driving dynamics and tire wear.
If the vehicle is measured front and rear, check and adjust the wheel alignment values at the rear axle first. Camber values at the front axle apply for the straight-ahead position of the wheels. Steering wheel and steering gear in centre position when toe is being adjusted.
Before wheel alignment values are adjusted at 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.
Vehicle height (height check)
General
The vehicle height at front and rear axle is not adjustable.
Preliminary work
For the height check, place the vehicle on a level surface or on the measuring platform (ready to drive, with a full tank, spare wheel and tools). Compress vehicle at front and rear by approximately 25 mm 2-3 times and allow it to spring back freely.
Front axle
Measure from road contact surface to the lower edge of the hexagon-head bolt of the tension-strut screw connection to the body.
Nominal values for front and rear axles are given in Adjusting Values For Suspension Alignment - 911 Carrera.
Rear axle
Measure from wheel contact surface to the locating bore in the rear-axle side section (between toe and camber eccentrics).
Wheel alignment
Notes
Only check or adjust wheel-alignment values when prescribed preconditions are met in Adjusting Values For Suspension Alignment - 911 Carrera.
If the vehicle is measured front and rear, check and adjust the rear axle first. Specifications
After adjustment, tighten the appropriate screwed connections with the prescribed tightening torque.
The steering angle sensor must be calibrated if the previous wheel alignment values (on rear and/or front axle) for vehicles with PSM were changed!
Caution! Malfunctions in the PSM control range if the steering angle sensor is not calibrated or is calibrated incorrectly.
^ Calibrate the steering angle sensor with the wheels in straight-ahead position.
Rear axle
Prepare vehicle for checking and/or adjustment of wheel alignment values. Place front heels on rotary table and rear wheels on rotary / sliding plates. Compress vehicle at front and rear by approximately 25 mm 2-3 times and allow it to spring back freely.
Adjusting toe
After loosening the lock nut, turn eccentric A appropriately.
Adjusting camber
After loosening the lock nut, turn eccentric B appropriately.
Note!
^ Use special tool 9626 in combination with a torque wrench to loosen and tighten the lock nuts of the toe and camber eccentrics. The prescribed lock nut tightening torque of 100 Nm (74 ft. lbs.) also corresponds to a setting on the torque wrench of approximately 100 Nm (74 ft. lbs.).
Front axle
Adjusting camber*
The camber is adjusted by moving the spring strut transversely. For this purpose, loosen the three fastening nuts on the spring-strut mount and, to move the spring strut, remove the covering cap on the piston rod.
Adjusting caster*
The caster is not adjustable on standard vehicles. In the event of repairs, a caster adjustment facility can be installed if necessary (as with the Boxster).
* The steering angle sensor must be calibrated if the previous wheel alignment values for vehicles with PSM (Porsche Stability Management) were changed!
Adjusting toe*
Preliminary work: Check whether the steering wheel is displaced with respect to the steering gear. To do this, centre the steering gear as described below.
Turn wheels to the straight-ahead position.
Then readjust the front wheel alignment, if necessary, until pin No. 2 in driver No. 1 and the lug on the steering gear housing No. 4 line up.
No. 3 is the desired breaking point for pins in new steering gears. (New) pin No. 2 is inserted into driver No. 1 and lies with its underside within the recess of lug No. 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 No. 3) by turning the steering wheel. The upper part of the pin remains in the driver.
If necessary, reposition the steering wheel. When doing this, seek the best position.
Warning! A triggering of the airbag (malfunction in the airbag system) caused by improper work on airbag components cannot be ruled out! In the case of such a malfunction, an unsuitable steering wheel holder could cause injury or damage!
^ Use only steering wheel holders which do not project into the area of the airbag unit!
^ Observe safety regulations when working with airbag vehicles!
Clamp steering wheel in centre position with steering wheel holder (Figure 106_96). Use only steering wheel holders which do not project into the area of the airbag unit! If necessary, shorten the guide rod (A) at top (arrow).
Then adjust toe at hexagon No. 2 of the track rod(s) after loosening the lock nut(s) No. 1 (Figure 133_1_96).
The steering angle sensor must then be calibrated in vehicles with PSM!
In order to tighten the tie rod lock nut(s) - to the prescribed tightening torque - use special tool 9625 in conjunction with a torque wrench (Figure 7_97). The prescribed lock nut tightening torque of 50 Nm (37 ft. lbs.) corresponds to a setting on the torque wrench of approximately 35 Nm (26 ft. lbs.).
Toe-difference angle
The toe-difference angle is not adjustable.
Special tool 9625