Wheel Alignment System: Adjustments GMC Terrain I

Wheel Alignment Measurement

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 in order to ensure correct alignment readings

1. Inspect for visuable damage to the suspension components and replace as necessary.
2. Inspect the tires for the proper inflation and irregular tire wear. Refer to «Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label»(ref-491131-S15122287122012073000000) , and «Tire Diagnosis - Irregular or Premature Wear»(ref-491142-S28858412872012073000000) .
3. Inspect the runout of the wheels and the tires. Refer to «Wheel Mounting Surface Check»(ref-491142-S23383030802012073000000) .
4. Inspect the wheel bearings for backlash and excessive play. Refer to «Wheel Bearings Diagnosis»(ref-491141-S06595892842012073000000) .
5. Inspect the ball joints for looseness or wear.
6. Inspect the tie rod ends for looseness or wear.
7. Inspect the control arms and stabilizer shaft for looseness or wear.
8. Inspect the steering gear for looseness at the frame. Refer to «Fastener Tightening Specifications»(ref-491181-S12032216182012073000000) .
9. Inspect the struts/shock absorbers for wear, leaks, and any noticeable noises. Refer to «Suspension Strut and Shock Absorber Testing - On Vehicle»(ref-491141-S15814032102012073000000) .
10. Inspect the vehicle trim height. Refer to «Trim Height Inspection»(ref-491141-S16372238572012073000000) .
11. Inspect the steering wheel for excessive drag or poor return due to stiff or rusted linkage or suspension components.
12. 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-491182-S23614206272012073000000) .

Front Caster Adjustment

The front caster is not adjustable. If the front caster angle is not within specifications, inspect for suspension support misalignment or front suspension damage. Refer to Wheel Alignment Specifications . Replace any damaged suspension components as necessary.

Front Camber Adjustment

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(ref-491131-S06536846302012073000000) .
2. Remove the wheel and tire assemblies. Refer to «Tire and Wheel Removal and Installation»(ref-491142-S07742607732012073000000) .
3. Remove the strut to knuckle nuts and bolts. Discard the nuts and bolts.
4. If the strut has not been previously modified, perform the following procedure: Disconnect the strut from the knuckle. NOTE: Maximum outboard adjustment-(increased negative camber) 2.0 mm of outboard elongation or to within 11.0 mm from outboard edge of lower strut clevis bracket, whichever comes first Maximum inboard adjustment-(increased positive camber) 4.0 mm of inboard elongation If filing the strut, paint the exposed metal with primer. If increasing negative camber, remove material from the outside of the lower strut hole. If decreasing negative camber, remove material from the inside of the lower strut hole.
5. Loosely install new strut to knuckle nuts and bolts.
6. Adjust the camber to specifications by moving the top of the wheel in or out as necessary. Refer to «Wheel Alignment Specifications»(ref-491182-S23614206272012073000000) .
7. Tighten strut to knuckle nuts and bolts to 180 N.m (133 lb ft).
8. Install the wheel and tire assemblies. Refer to «Tire and Wheel Removal and Installation»(ref-491142-S07742607732012073000000) .

Wheel Alignment - Steering Wheel Angle and/or Front Toe Adjustment

1. Position and lock the steering wheel with the vehicle with the wheels in the straight forward position.
2. Loosen both inner tie rod jam nuts.
3. Loosen the inner tie rod seal to boot surface.
4. Use a wrench on the tie rod flats to increase or decrease the toe angle specifications. Refer to «Wheel Alignment Specifications»(ref-491182-S23614206272012073000000) .
5. Tighten the inner tie rod jam nuts to 70 N.m (52 lb ft).
6. Inspect the toe angle to ensure proper adjustment and adjust as necessary.

Rear Camber Adjustment

1. Loosen the upper control arm-to-frame fastener enough to allow movement.
2. Rotate the upper control arm-to-frame fastener in the direction necessary to the correct the camber measurement.
3. Snug the upper control arm-to-frame fastener, do not tighten at this time.
4. Reinspect the rear camber specifications and adjust as necessary.
5. Hold the nut and tighten the upper control arm-to-frame bolt to 164 N.m (121 lb ft).
6. Repeat the procedure for the other rear wheel.

Rear Toe Adjustment

1. Loosen the suspension adjustment link-to-frame fastener enough to allow for movement.
2. Rotate the suspension adjustment nut in the direction necessary to correct the toe angle.
3. Snug the suspension adjustment link-to-frame fastener, do not tighten at this time.
4. Reinspect the rear toe specifications and adjust as necessary.
5. Hold the nut and tighten the link-to-frame fastener bolt to 164 N.m (121 lb ft).
6. Repeat the procedure for the other rear wheel.

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.

Cross Camber is the difference between the left camber value and the right camber value.

Cross Camber = L camber - R camber

Scheme 5

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. 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.

Cross Caster is the difference between the left caster value and the right caster value.

Cross caster = L caster - R caster