Wheel Alignment Specifications & Adjustment Procedures Buick Century VI

Wheel Alignment Specifications

Fastener Tightening Specifications

Fastener Tightening Specifications

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 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 Tires and Wheels 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 TIRE DIAGNOSIS - IRREGULAR OR PREMATURE WEAR in Tires and Wheels.
2. Inspect the runout of the wheels and the tires. Refer to Tire and Wheel Runout Specifications in Vibration Diagnosis and Correction.
3. Inspect the wheel bearings for backlash and excessive play. Refer to Wheel Bearings Diagnosis in Suspension General Diagnosis.
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. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
6. Inspect the steering gear for looseness at the frame. Refer to FASTENER TIGHTENING SPECIFICATIONS in Power Steering System.
7. Inspect the struts/shock absorbers for wear, leaks, and any noticeable noises. Refer to Struts or Shock Absorbers On-Vehicle Testing in Suspension General Diagnosis.
8. Inspect the vehicle trim height. Refer to Trim Height Inspection Procedure in Suspension General Diagnosis.
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. IMPORTANT: When performing adjustments to vehicles requiring a 4-wheel alignment, set the rear wheel alignment angles first in order to obtain proper front alignment angles.
4. Adjust alignment angles to vehicle specification, if necessary. Refer to «WHEEL ALIGNMENT SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/wheel-alignment/#wheel-alignment-specifications-adjustment-procedures) .

Scheme 1

1. Raise the vehicle and provide suitable support. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information.
2. Remove the tire and wheel assemblies from the front and the rear axles. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION in Tires and Wheels.
3. Remove the strut from the vehicle. Refer to STRUT, STRUT COMPONENT AND/OR SPRING REPLACEMENT in Front Suspension.
4. Place the strut in a vise and file the hole lateral - oblong. Compare the appearance of the holes before filing (2) with after filing (3).
5. File the lower strut-to-knuckle attaching hole for a front camber adjustment.

Installation Procedure

Note. Refer to FASTENER NOTICE in Cautions and Notices.

Scheme 2

1. Install the strut to the vehicle. Refer to STRUT, STRUT COMPONENT AND/OR SPRING REPLACEMENT in Front Suspension. Tighten Tighten the strut-to-knuckle bolts as far as to allow movement of the knuckle.
2. Install the tire and wheel assemblies. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION in Tires and Wheels.
3. Adjust the camber (1). Tighten Tighten the strut-to-knuckle bolts to 122 N.m (90 lb ft).
4. Lower the vehicle.

Scheme 3

1. Perform the following steps to remove the small seal clamp
2. Position the steering wheel in the straight ahead position.
3. Loosen the hex nut on the tie rod (2). Turn the tie rod shaft (1) in order to obtain the proper toe angle. Refer to «WHEEL ALIGNMENT SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/wheel-alignment/#wheel-alignment-specifications-adjustment-procedures) .
4. Confirm the number of threads showing on each tie rod end is nearly equal. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
5. Confirm that the tie rod ends (3) are square before you tighten the lock nuts (2). Tighten Tighten the hex nuts at the tie rod ends to 68 N.m (50 lb ft). IMPORTANT: Ensure the seals do not twist.
6. Install the seal clamps.

Scheme 4

1. Raise the vehicle and provide suitable support. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information.
2. Remove the tire and wheel assemblies. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION in Tires and Wheels.
3. Remove the strut from the vehicle. Refer to Strut Assembly Replacement in Rear.
4. Place the strut in a vise and file the upper strut-to-knuckle hole lateral (oblong). Compare the appearance of the holes before filing (2) with after filing (3).

Note. Refer to FASTENER NOTICE in Cautions and Notices.

Scheme 5

1. Install the strut to the vehicle. Refer to Strut Assembly Replacement in Rear. Tighten Tighten the strut-to-knuckle bolts as far as to allow movement of the knuckle.
2. Install the tire and wheel assemblies. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION in Tires and Wheels.
3. Adjust the camber (1). Tighten Tighten the strut-to-knuckle bolts to 122 N.m (90 lb ft).
4. Lower the vehicle.

Scheme 6

Scheme 7

Scheme 8

1. Loosen the hex nuts at the rear wheel spindle rod (rear).
2. Turn the adjusting nut to change the toe angle.
3. Adjust the toe to the proper setting. Refer to «WHEEL ALIGNMENT SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/wheel-alignment/#wheel-alignment-specifications-adjustment-procedures) . NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
4. Tighten the hex nuts on the rear wheel spindle rod (rear). Tighten Tighten the rear wheel spindle rod ends hex nuts to 50 N.m (37 lb ft).

Caster Description

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 9

Camber Description

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 10

Toe Description

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.

Scheme 11

Setback Description

Setback applies to both the front and the rear wheels. Setback is the amount that one wheel may be aligned behind the other wheel. Setback may be the result of a road hazard or a collision. The first clue is a caster difference from side-to-side of more than 1 degree.

Thrust Angles Description

The front wheels aim or steer the vehicle. The rear wheels control tracking. This tracking action relates to the thrust angle (3). The thrust angle is the path that the rear wheels take. Ideally, the thrust angle is geometrically aligned with the body centerline (2).

In the illustration, toe-in is shown on the left rear wheel, moving the thrust line (1) off center. The resulting deviation from the centerline is the thrust angle.

Scheme 12

Lead/Pull Description

Lead/pull is the deviation of the vehicle from a straight path, on a level road, without hand pressure on the steering wheel.

Lead/pull is usually caused by the following factors

1. Tire construction
2. Uneven brake adjustment
3. Wheel alignment

The way in which a tire is built may produce lead/pull. The rear tires will not cause lead.

Torque Steer Description

A vehicle pulls or leads in one direction during hard acceleration. A vehicle pulls or leads in the other direction during deceleration.

The following factors may cause torque steer to be more apparent on a particular vehicle

1. A slightly smaller diameter tire on the right front increases a right torque lead. Inspect the front tires for differences in the brand, the construction, or the size. If the tires appear to be similar, change the front tires from side-to-side and retest the vehicle. Tire and wheel assemblies have the most significant effect on torque steer correction.
2. A large difference in the right and left front tire pressure
3. Left-to-right differences in the front view axle angle may cause significant steering pull in a vehicle. The pull will be to the side with the most downward sloping axle from the differential to the wheels. Axles typically slope downward from the differential. The slope of the transaxle pan to level ground may be used as an indication of bias axle angles. The side with the higher transaxle pan (shown on the left side of the illustration) has the most downward sloping axle angle.

Memory Steer Description

Memory steer is when the vehicle wants to lead or pull in the direction the driver previously turned the vehicle. Additionally, after turning in the opposite direction, the vehicle will want to lead or pull in that direction.

Wander Description

Wander is the undesired drifting or deviation of a vehicle to either side from a straight path with hand pressure on the steering wheel. Wander is a symptom of the vehicle's sensitivity to external disturbances, such as road crown and crosswind, and accentuated by poor on-center steering feel.

Scrub Radius Description

Ideally, the scrub radius is as small as possible. Normally, the SAI angle and the centerline of the tire and the wheel intersect below the road surface, causing a positive scrub radius. With struts, the SAI angle is much larger than the long arm/short arm type of suspension. This allows the SAI angle to intersect the camber angle above the road surface, forming a negative scrub radius. The smaller the scrub radius, the better the directional stability. Installing aftermarket wheels that have additional offset will dramatically increase the scrub radius. The newly installed wheels may cause the centerline of the tires to move further away from the spindle. This will increase the scrub radius.

A large amount of scrub radius can cause severe shimmy after hitting a bump. Four-wheel drive vehicles with large tires use a steering damper to compensate for an increased scrub radius. Scrub radius is not directly measurable by the conventional methods. Scrub radius is projected geometrically by engineers during the design phase of the suspension.

See also:
• FASTENER NOTICE
• LIFTING AND JACKING THE VEHICLE
• WHEEL ALIGNMENT SPECIFICATIONS