GM Century/Lumina/Grand Prix/Intrigue 1997-2000

Wheel Alignment



Wheel alignment refers to the angular relationship between the wheels, the suspension attaching points and the ground.

On the W-Body vehicles covered by this guide, GM specifies that Four Wheel Alignment be used, since the rear suspension is independent and adjustable, not a solid beam axle used on some other Front Wheel Drive vehicles. A complete four wheel alignment check is recommended whenever a service check is deemed necessary (uneven tire wear, the vehicle pulls to one side or a major suspension component has been replaced). This check includes the measurement of all four tires. The fuel economy and tire life increases when the vehicle is geometrically aligned. Additionally, the steering and the vehicle performance is maximized.

Because four wheel alignment is critical to the vehicle's performance and safety, it should be performed by a qualified technician with the proper equipment. The latest alignment equipment uses lasers for accurate sighting and a computer for precise calculations. Below is a description of the various angles used in wheel alignment on these vehicles.


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Fig. Caster is the tilting of the uppermost point of the steering axis, either forward or backward

Caster is the tilting of the uppermost point of the steering axis, either forward or backward from vertical, when viewed from the side of the vehicle. A backward tilt at the top is called positive caster (+) and a forward tilt is called negative caster (-). Caster influences the directional control of the steering, but caster does not affect tire wear. One wheel with more positive caster than the other wheel causes that wheel to pull toward the center of the vehicle. The vehicle will move or lead toward that side with the least amount of caster.


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Fig. Camber is the tilting of the wheels from vertical as viewed from the front

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 said to be positive (+). When the wheels tilt inward, the camber is said to be negative (-). The amount of tilt, measured in degrees, from the vertical is known as camber angle. Camber influences both directional control and tire wear. Excessive camber results in tire wear and causes the vehicle to pull or lead to the side with the most positive camber. On GM W-Body vehicles, camber adjustment is available at both the front and rear wheels.


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Fig. Toe-in is the turning in of the wheels; toe-out is the turning out of the wheels, from the vehicle centerline

Toe-in is the turning-in of the wheels, while toe-out is the turning-out of the wheels from the geometric centerline. The purpose of toe is to ensure parallel rolling of the wheels. Toe also serves to offset the small deflections of the wheel support system which occur whenever the vehicle is rolling forward. Even when the wheels are set to toe-in or toe-out, the wheels tend to roll parallel on the road when the vehicle is moving.

Frame Misalignment

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Fig. Subframe misalignment can result from collision damage or poorly performed heavy service work where the subframe is loosened or lowered

The frame is a rubber isolated subframe (so-called on these vehicles because it does not run the full length of the vehicle), in the front of the vehicle. The subframe supports the engine and transaxle. The frame provides the mounting point for the front suspension lower control arms. Any misalignment of the subframe (accident damage, improperly performed heavy engine work where the subframe is loosened, lowered and/or removed, etc.) causes a misalignment of the front wheels. Movement of the frame usually causes an increase in caster on one side of the vehicle and decrease in caster on the other side. This can cause the exhaust system to bind up, problems with control cables and unacceptable noise. Check the subframe for any obvious damage, especially on a used vehicle with an unknown history.


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Fig. Subframe setback could result from a road hazard or collision

Setback applies to both the front and the rear wheels. Setback is the amount that one wheel spindle may be aligned behind the other wheel spindle. Setback may be the result of a road hazard (heavily hit pothole, for example) or a collision. The first clue is a caster difference from side-to-side of more than one degree.

Thrust Angles

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Fig. Thrust angle is the path that the rear wheels take

The front wheels aim or steer the vehicle. The rear wheels control tracking. This tracking action relates to the thrust angle. The thrust angle is the path that the rear wheels take. Ideally the thrust angle is geometrically aligned with the body centerline. If, for example, the toe-in on the left rear wheel is out of specification, it moves the thrust line off center. The resulting deviation from the centerline is the thrust angle.


Lead is the deviation of the vehicle from a straight path on a level road, without hand pressure on the steering wheel. Lead is usually the result of tire construction, uneven parking brake adjustment or the wheel alignment. The way in which a tire is built may produce lead. Rear tires do not cause lead.

Torque Steer

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Fig. Torque steer is when the vehicle leads in one direction on acceleration and another direction during deceleration

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:

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.
A large difference in the right and left front tire pressure.
Left-to-right differences in the front view axle angle may cause significant steering pull in the vehicle. The pull will be to the side with the most downward sloping axle from the differential to the wheels. Axles (halfshafts) 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 has the most downward sloping axle angle.

Memory Steer

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, th