Wheel Alignment
STANDARD PROCEDURE - WHEEL ALIGNMENTNOTE: The front and rear wheel alignment must be checked and adjusted to the preferred specifications with the vehicle at Curb Height rather than at Design Height.
1. Correctly position the vehicle on wheel alignment equipment per the equipment manufacturer's recommendations.
2. Perform a pre-wheel alignment inspection.
NOTE: When the front and rear height checking fixture is installed on the wheels, they must be positioned at the very bottom of the wheel inner flange. This is required to ensure the height checking fixtures are parallel to the bottom surface of the frame rails, which is required to achieve an accurate vehicle curb height measurement.
3. Measure the vehicles curb height.
4. Attach the wheel alignment equipment following the equipment manufacturer's instructions.
Align the vehicle starting with the rear suspension, then proceeding to the front suspension. Always set toe last.
5. Proceed with Camber And Caster Angle.
CAMBER AND CASTER ANGLE
The camber and caster angles on this vehicle are adjustable using cams located on the lower control arm bushing pivot bolts. Correct camber and caster specifications are obtained by simultaneously rotating front and rear adjustment cams until lower control arm is correctly positioned.
CAUTION: Prior to any cam bolt rotation, locknuts must be loosened to ends of pivot bolt threads. This must be done to allow lower control arm mounting brackets to be spread, allowing free movement of bushings. If not done, serious bracket bending, weld breakage of cam retainer, free cam and cam bolt shank fracturing, or thread damage can occur. It may be necessary to tap bracket ears away from bushings to allow unrestricted cam bolt movement.
INCLINOMETER SETUP FOR CASTER ANGLE VIEWING
Both front and rear caster angle on this vehicle can be read. This is accomplished by reading caster directly off the front and rear knuckles through inclinometer sensors attached to the DRBIII scan tool, rather than using the alignment machine's sweep method. Use Special Tools 6989, 6996, 6915, and 6916, which are included in the 1996 Essential Viper Alignment Package.
NOTE: It is necessary to have a DRBIII with an attached PEP module capable of reading inclinometers.
1. Plug the cable from the switch box, Special Tool 6996, into the pep module connector on the DRBIII marked "INCL."
2. Plug the power cable (supplied with the DRBIII kit) into the DRBIII power connector marked "VEHICLE."
3. Attach the two inclinometers, Special Tool 6989, to the switch box. Only two inclinometers are supplied and should be used as a pair to measure either rear caster or front caster, one at a time.
4. Attach the power cable from the DRBIII to the vehicle data connector.
5. Select the Stand Alone DRBIII option from the Main Menu screen.
6. Select the Inclinometer option from the Stand Alone Main Menu.
7. Select the Read/Display Angle option from the Inclinometer Main Menu. This option is used to zero the inclinometers before use on the vehicle. The inclinometer, Special Tool 6989, must be zeroed (calibrated) prior to each time it will be used to read the caster angle on the vehicle. This screen shows the readout for the left and right inclinometers.
8. Press F3 to show both inclinometers.
9. Zero the inclinometers: Place both inclinometers together on a known flat, level surface, such as the alignment rack, with the knurled ends of the fastening screws facing upward. Press F2. This zeros the inclinometers in one direction. Rotate the inclinometers 180 degrees in place, then press F2 again to zero both inclinometers in the other direction. The inclinometers are now ready to be installed on the vehicle.
10. Mount inclinometers to either both rear or both front Caster Angle Fixtures, Special Tool 6916 or 6915. Make sure the inclinometer from the left side of the switch box is mounted to the left fixture and the inclinometer from the right side of the switch box is mounted to the right fixture.
11. Once inclinometers are mounted on Caster Angle Fixtures, they can be mounted on either the rear knuckle caster angle pads as shown. The caster pads are located on the front edge of the front steering knuckle and the rear edge of rear knuckle. Be sure caster pads are thoroughly cleaned before mounting the Caster Inclinometers on the knuckles. Caster Inclinometers must sit flat on caster pads to obtain accurate caster readings.
NOTE: It may be necessary to remove the ABS wheel speed sensors from the knuckles in order to properly install the caster angle fixtures on the vehicle.
12. Adjust caster using the measurements viewed on the DRBIII screen, and camber using the measurements viewed on the alignment equipment.
13. When adjustments are complete, transfer the inclinometers to the other set of fixtures to measure front or rear caster which has yet to be measured.
CAMBER ANGLE
Camber angle adjustment involves the repositioning of the lower control arm pivot bolts using the adjustment cams. There are 2 cams located on each lower control arm pivot bolt, 4 per each corner of the vehicle front and rear. Repositioning of the pivot bolt cams moves the lower ball joint in or out to obtain the required camber specifications.
CASTER ANGLE
Caster angle adjustment, like camber angle adjustment, involves the repositioning of the lower control arm pivot bolts using the adjustment cams. There are 2 cams located on each lower control arm pivot bolt, 4 per each corner of the vehicle front and rear. Repositioning of the pivot bolt cams moves the lower ball joint fore or aft as required to obtain the required caster specifications.
FRONT AND REAR TOE
The static toe position should be the final adjustment made to the vehicle during the alignment procedure.
NOTE: When setting front and rear wheel static toe position, it is recommended to leave the engine running during the front wheel toe setting procedure.
1. Start the engine and turn wheels both ways before straightening and centering steering wheel. Center steering wheel and retain with steering wheel clamp.
2. Remove clamp from steering gear boot attaching it to inner tie rod.
3. Loosen inner to outer tie rod end jam nut.
CAUTION: Do not twist inner tie rod to steering gear rubber boots during this adjustment.
4. Grasp inner tie rod at adjustment serration. Rotate inner tie rod in direction required to obtain specified individual wheel toe position.
5. Torque inner tie rod to outer tie rod housing locknut to 75 Nm (55 ft. lbs.).
6. Adjust steering gear to inner tie rod boots at inner tie rod so boots are not twisted. Then install steering gear boot to inner tie rod boot clamp at tie rod.
7. Remove steering wheel clamp.
8. Remove all alignment equipment from vehicle.
9. Remove caster angle inclinometers from front or rear knuckles.
ADJUSTMENTS - CURB HEIGHT (STANDARD SUSPENSION)
On vehicles with the standard suspension, spring shims or reduced height seats may be installed on the front or rear shock assemblies. Spring shim installation increases coil spring preload, thus raising the curb height of the vehicle. Reduced spring seat installation decreases coil spring preload, thus lowering the curb height of the vehicle.
Keep in mind the following when considering adjusting coil spring preload:
- Use only this method to obtain correct curb height.
- Install shims or spring seats only on vehicles that do not meet curb height specifications.
- Adjust either both front or both rear shock assemblies the same amount.
CAUTION:
- Do not stack spring shims; only one shim can be installed per shock assembly.
- Do not use both a spring shim and a reduced height spring seat on the same shock assembly.
The shock assembly must be removed from the vehicle to perform this procedure.
For the disassembly and assembly of the shock absorber assembly, use Strut Spring Compressor, Pentastar Service Equipment (PSE) tool W-7200, or the equivalent, to compress the coil spring. Follow the manufacturer's instructions closely.
1. If both shock absorber assemblies are being removed and serviced at the same time, mark the coil spring and shock absorber assembly according to which side of the vehicle the shock absorber was removed from.
2. Position the shock absorber assembly in the strut coil spring compressor following the manufacturers instructions. First, set the lower hooks on the coil spring, then set the upper hooks.
3. Compress the coil spring until enough room is given to remove the coil spring upper seat.
4. Remove the coil spring upper seat. To remove the upper seat, pull up on the shock absorber and remove the seat utilizing the cutout in its side.
5. Perform one of the following:
- If the vehicle was lower than curb height specification, add a maximum of 1 spring shim under the upper spring seat.
- If vehicle was higher than curb height specification, replace the original upper spring seat with a reduced height spring seat.
6. Holding the shock upward, install the upper seat (with shim where applicable) on the shock absorber utilizing the cutout in the seat.
7. Position the upper seat on the top of the coil spring so the cutout in the upper seat (and shim where applicable) is not positioned at the upper end of the coil spring.
8. Slowly release the tension from the coil spring by backing off the compressor drive completely. As the tension is relieved, make sure the coil spring, upper and lower seats, and shock absorber align properly.
9. Push back the spring compressor upper and lower hooks, then remove the shock absorber assembly from the spring compressor.
10. Install the shock assembly on the vehicle.
ADJUSTMENTS - CURB HEIGHT (ACR SUSPENSION)
NOTE: Lowering the vehicle more than 1" from the factory curb (ride) height settings is not recommended.
NOTE: Always check the wheel alignment after lowering or raising the vehicle.
1. Raise the vehicle.
2. Remove the wheel and tire assembly.
3. The shock assembly lower spring seat houses two grub screws that thread into the spring seat to ensure proper locking of the ring. Loosen these screws using the hex bit on the supplied tool. DO NOT attempt to remove or replace them.
4. Insert the 6 mm pin, located on the supplied tool, into one of the holes located on the edge of the lower spring seat.
5. Turn the spring seat clockwise to raise the ride height; counterclockwise to lower it.
- Front - 1 complete rotation of the spring seat changes the ride height 3.0 mm (0.120 inch).
- Rear - 1 complete rotation of the spring seat changes the ride height 3.6 mm (0.140 inch).
6. Once the desired ride height is achieved, lock the lower spring seat into position by using the hex bit to tighten the grub screws snugly. DO NOT overtighten the grub screws.
7. Repeat above steps as necessary on remaining ACR shock assemblies.
8. Install the wheel and tire assembly.
9. Lower the vehicle.
10. Measure curb height.
ADJUSTMENTS - DYNAMIC TOE PATTERN
The Viper suspension system is designed to vary the wheel toe pattern according to the vehicle ride posture to keep the wheels pointed in the proper direction at all times. The four wheel independent suspension alignment must be correct to assure proper road handling. The frame and suspension components are calibrated at the assembly plant and should not require adjustment unless the vehicle has collision damage. This section will cover procedures for correcting improper frame, steering gear, and rear toe link alignment that would affect the wheel toe pattern. Before performing the following operations, verify that the front and rear wheel alignment and vehicle height is within specifications.
Wheel toe pattern is regulated by the vertical positioning of the inner tie rod pivot in relation to the orbital swing of the wheel spindle. Wheel toe settings have no effect on toe pattern. When the suspension is fully compressed and then extended with the tie rod disconnected from the spindle, the spindle makes an arc in space without altering the toe pattern. When the arc of the spindle is extended into a full circle and the inner tie rod end is positioned in the center of the circle, the toe pattern cannot change. When the inner tie rod end is raised or lowered from the center of the true circle of the spindle arc, the toe pattern will vary. When the suspension is compressed (jounce), the wheel toe should change from normal riding height. When the suspension is extended (rebound), wheel toe should move in the opposite direction. The front suspension jounce should cause toe-out, rebound should cause toe-in. Rear suspension jounce should cause toe- in, rebound should cause toe-out.
TOE PATTERN PREPARATION
Before toe pattern can be inspected, vehicle design height, suspension settings and design bushing position must be established.
- Verify that all fluid reservoirs and fuel tank is full.
- Position the vehicle on a known level surface (suspension or frame alignment rack).
- Remove all objects from the vehicle that were not installed at the assembly plant.
- Inflate tires to the specification found on the tire inflation sticker on the left door end frame.
- Disconnect front and rear stabilizer bar links from lower control arms.
- Verify vehicle design height, caster, camber and toe settings are within specifications.
TOE PATTERN INSPECTION
NOTE: Toe Pattern Preparation procedures must be performed before toe pattern inspection.
1. Position bottle jacks (or equivalent) at the rear PLP (gauge) holes and at the center of the front crossmember.
2. Hoist vehicle and remove the wheels.
3. Remove front and rear coil-over-shock assemblies.
4. Install wheels.
5. Lower vehicle so the top of each lifting pad on the jacks is 123 mm (5 inch) above the base of each tire. At this setting, the vehicle is at design height.
6. Measure front and rear wheel toe at design height and record measurement in degrees on the Toe Pattern Graph.
7. Raise front and rear of vehicle 25 mm (1 inch) above design height. Measure and record front and rear toe.
a. Raise front and rear of vehicle 50 mm (2 inch) above design height. Measure and record front and rear toe.
9. Return vehicle to design height.
10. Lower front and rear of vehicle 25 mm (1 inch) below design height. Measure and record front and rear wheel toe.
11. Lower front and rear of vehicle 50 mm (2 inch) below design height. Measure and record front and rear wheel toe.
NOTE: It may not be possible to obtain a wheel toe reading with the vehicle lowered 50 mm (2 inch) below design. If not, use readings from other height settings to determine toe pattern arc.
12. Plot toe readings for the front suspension on the Toe Pattern Graph. If toe pattern arc is within allotted area, front toe pattern is within limits. If toe pattern is not within allotted area, the steering gear must be raised or lowered to achieve proper toe pattern.
13. Plot toe readings for the rear suspension on the Toe Pattern Graph. If toe pattern arc is within allotted area, rear toe pattern is within limits. If toe pattern is not within allotted area, the inner pivot of the toe links must be raised or lowered to achieve proper toe pattern.
TOE PATTERN ADJUSTMENT
After a toe pattern arc has been plotted, and is outside of allotted area on the graph, the steering gear, rear toe links or both must be adjusted.
If the front toe pattern requires adjustment, the steering gear can be raised using split shims. If the steering gear must be lowered, the gear mountings are misaligned and will require alignment.
If the rear toe pattern requires adjustment, the rear toe links can be raised or lowered using toe link shims. The rear toe links are mounted to the frame in vertical elongated holes that allow the toe link to be moved up or down. Toe link shims in increments of 2 mm (0.080 inch) above or below design (nominal) are used to position the toe link.
A 2 mm (0.080 inch) change in steering gear or toe link height will effect the toe pattern by about 0.15° when measured from the design height (nominal) to either jounce or rebound positions. It is typical for a shim to have about 1 mm (0.040 inch) up and down play.
FRONT TOE PATTERN
On the front of the vehicle, the tie rods are located in front of the spindles. If the steering gear is raised, toe-in will increase on rebound and toe-out will increase on jounce. If the steering gear is lowered, the opposite would occur. The front toe pattern should arc from (-)0.10°; toe-out at 50 mm (2 inch) jounce to (+)0.20°; toe-in at 50 mm (2 inch) rebound.
REAR TOE PATTERN
On the rear of the vehicle, the tie rods (toe links) are located rearward of the spindles. If a toe link is raised, toe-out will increase on rebound and toe-in will increase on jounce. If a toe link is lowered, the opposite will occur. The toe pattern should arc from (+)0.30°; toe-in at 50 mm (2 inch) jounce to 0.00°; toe at 50 mm (2 inch) rebound.
SUSPENSION COMPONENT INSTALLATION
After toe pattern has been inspected or adjusted, perform the following procedures.
- Install the coil-over-shock assemblies.
- Connect stabilizer bar links to lower control arms.
- Verify wheel alignment toe setting.
- Road test vehicle to determine if problem is corrected.
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TOE PATTERN GRAPH