Wheel Alignment System: Adjustments Chevrolet Uplander I

Measuring Wheel Alignment

Steering and vibration complaints are not always the result of improper alignment. One possible cause is wheel and tire imbalance. Another possibility is tire lead due to worn or improperly manufactured tires. Lead/pull is defined as follows: At a constant highway speed on a typical straight road, lead/pull is the amount of effort required at the steering wheel to maintain the vehicle's straight path. Lead is the vehicle deviation from a straight path on a level road without pressure on the steering wheel. Refer to Radial Tire Lead/Pull Correction in order to determine if the vehicle has a tire lead problem.

Before performing any adjustment affecting wheel alignment, perform the following inspections and adjustments in order to ensure correct alignment readings

1. Inspect the tires for the proper inflation and irregular tire wear. Refer to «Label - Vehicle Certification, Tire Place Card, Anti-Theft and Service Parts ID»(ref-241684-S12481183632006081100000) and «Tire Diagnosis - Irregular or Premature Wear»(ref-241703-S25108877712006081100000) .
2. Inspect the runout of the wheels and the tires. Refer to «Tire and Wheel Runout Specifications»(ref-241742-S19000912392006081100000) .
3. Inspect the wheel bearings for backlash and excessive play. Refer to «Wheel Bearings Diagnosis»(ref-241733-S24986711582006081100000) .
4. Inspect the ball joints and tie rod ends for looseness or wear.
5. Inspect the control arms and stabilizer shaft for looseness or wear.
6. Inspect the steering gear for looseness at the frame. Refer to «Fastener Tightening Specifications»(ref-241712-S14509571502006081100000) .
7. Inspect the struts/shock absorbers for wear, leaks and any noticeable noises. Refer to «Struts or Shock Absorbers On-Vehicle Testing»(ref-241733-S17909397662006081100000) .
8. Inspect the vehicle trim height. Refer to «Trim Height Inspection Procedure»(ref-241733-S08679009162006081100000) .
9. Inspect the steering wheel for excessive drag or poor return due to stiff or rusted linkage or suspension components.
10. Inspect the fuel level. The fuel tank should be full or the vehicle should have a compensating load added.

Give consideration to excess loads, such as tool boxes, sample cases, etc. If normally carried in the vehicle, these items should remain in the vehicle during alignment adjustments. Give consideration also to the condition of the equipment being used for the alignment. Follow the equipment manufacturer's instructions.

Satisfactory vehicle operation may occur over a wide range of alignment settings. However, if the setting exceeds the service allowable specifications, correct the alignment to the service preferred specifications. Refer to Wheel Alignment Specifications .

Perform the following steps in order to measure the front and rear alignment angles

1. Install the alignment equipment according to the manufacturer's instructions.
2. Jounce the front and the rear bumpers 3 times prior to checking the wheel alignment.
3. Measure the alignment angles and record the readings.
4. Adjust alignment angles to vehicle specification, if necessary. Refer to «Wheel Alignment Specifications»(ref-241714-S26571622512006081100000) .

Front Camber Adjustment

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(ref-241684-S36257494482006081100000) in General Information.
2. Remove the tire and wheel. Refer to «Tire and Wheel Removal and Installation»(ref-241703-S14581567662006081100000) in Tires and Wheels.
3. Remove the strut lower bolt in order to inspect for an oblong strut lower hole (3). If the strut lower hole is oblong, loosen the strut upper bolt in order to allow for camber adjustment. If the strut lower hole is NOT oblong, perform the following steps: Remove the strut from the vehicle. Refer to «Strut Assembly Replacement»(ref-241710-S01746452062006081100000) in Front Suspension. Secure the strut in a vise. File the strut lower hole laterally (3) in order to allow for camber adjustment. Install the strut to the vehicle. Refer to «Strut Assembly Replacement»(ref-241710-S01746452062006081100000) in Front Suspension. Install the strut bolts.
4. Adjust the camber. Tighten: Tighten the strut lower nuts to 123 N.m (90 lb ft).
5. Install the tire and wheel. Refer to «Tire and Wheel Removal and Installation»(ref-241703-S14581567662006081100000) in Tires and Wheels.
6. Lower the vehicle.

Front Toe Adjustment

1. Remove the power steering gear seal small clamps.
2. Verify that the steering wheel is centered and the wheels are in the straight ahead position.
3. Loosen the left and right tie rod jam nuts (2).
4. Rotate the inner tie rods in order to obtain the proper toe angle of 0 degrees.
5. Tighten the tie rod end jam nuts. Tighten: Tighten the left and right tie rod jam nuts (2) to 68 N.m (50 lb ft).
6. Install the power steering gear seal small clamps.

Rear Toe Adjustment

1. Loosen the jam nut (6) at the rear wheel tie rod.
2. Adjust the toe to the proper setting by turning the inner link adjustment hex (4). Refer to «Wheel Alignment Specifications»(ref-241714-S26571622512006081100000) .
3. When the toe adjustment is correct, tighten the jam nut. Tighten: Tighten the nut to 62 N.m (45 lb ft).
4. Recheck the toe alignment.

Scheme 3

Caster is the tilting of the uppermost point of the steering axis either forward or backward, when viewed from the side of the vehicle. A backward tilt is positive (+) and a forward tilt is negative (-). Caster influences directional control of the steering but does not affect the tire wear and is not adjustable on this vehicle. Caster is affected by the vehicle height, therefore it is important to keep the body at its designed height. Overloading the vehicle or a weak or sagging rear spring will affect caster. When the rear of the vehicle is lower than its designated trim height, the front suspension moves to a more positive caster. If the rear of the vehicle is higher than its designated trim height, the front suspension moves to a less positive caster.

With too little positive caster, steering may be touchy at high speed and wheel returnability may be diminished when coming out of a turn. If one wheel has more positive caster than the other, that wheel will pull toward the center of the vehicle. This condition will cause the vehicle to pull or lead to the side with the least amount of positive caster.

Scheme 4

Camber is the tilting of the wheels from the vertical when viewed from the front of the vehicle. When the wheels tilt outward at the top, the camber is positive (+). When the wheel tilts inward at the top, the camber is negative (-). The amount of tilt is measured in degrees from the vertical. Camber settings influence the directional control and the tire wear.

Too much positive camber will result in premature wear on the outside of the tire and cause excessive wear on the suspension parts.

Too much negative camber will result in premature wear on the inside of the tire and cause excessive wear on the suspension parts.

Unequal side-to-side camber of 1 degree or more will cause the vehicle to pull or lead to the side with the most positive camber.

Scheme 5

Toe is a measurement of how much the front and/or rear wheels are turned in or out from a straight-ahead position. When the wheels are turned in, toe is positive (+). When the wheels are turned out, toe is negative (-). The actual amount of toe is normally only a fraction of a degree. The purpose of toe is to ensure that the wheels roll parallel.

Toe also offsets the small deflections of the wheel support system that occur when the vehicle is rolling forward. In other words, with the vehicle standing still and the wheels set with toe-in, the wheels tend to roll parallel on the road when the vehicle is moving.

Improper toe adjustment will cause premature tire wear and cause steering instability.