Dynamic Toe Pattern

OVERVIEW
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 suspension alignment and vehicle height is within specifications. Refer to Wheels, Tires and Alignment, Alignment, Adjustments for proper procedures.






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. Refer to Suspension, Stabilizer Bar, Service and Repair for proper procedures.
- Verify vehicle design height, caster, camber and toe settings are within specifications. Refer to Wheels, Tires and Alignment, Alignment, Adjustments for proper procedures.

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. Refer to Suspension, Shock Absorber, Service and Repair for proper procedures.
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 provided.
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 or 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 shaded area, front toe pattern is within limits. If toe pattern is not within shaded 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 shaded area, rear toe pattern is within limits. If toe pattern is not within shaded area, the inner pivot of the toe links must be raised or lowered to achieve proper toe pattern.





TOE PATTERN GRAPH

TOE PATTERN ADJUSTMENT
After a toe pattern arc has been plotted, and is outside of shaded 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 would require alignment. Refer the Frame Dimensions to determine the design height of the steering gear mounts.
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. To 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. Refer to Steering for steering gear service procedure.

REAR TOE PATTERN
On the rear of the vehicle, the tie rods 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 would 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. Refer to Suspension, Tie Rod, Rear Suspension for Toe Link Service Procedures.

SUSPENSION INSTALLATION
After toe pattern has been inspected or adjusted, perform the following procedures.
- Install the coil-over-shock assemblies. Refer to Front, or Rear Suspension for proper tightening procedures.
- Connect stabilizer bar links to lower control arms.
- Verify wheel toe setting.
- Road test vehicle to determine if problem is corrected.

Dynamic Toe Pattern: