Wheel Alignment System Cadillac STS I

Wheel Alignment Specifications

Wheel Alignment Specifications

Trim Height Specifications

Trim Height Specifications

Fastener Tightening Specifications

Fastener Tightening Specifications

Trim Height Measurements

Trim height is a predetermined measurement relating to vehicle ride height. Incorrect trim heights can cause bottoming out over bumps, damage to the suspension components and symptoms similar to wheel alignment problems. Check the trim heights when diagnosing suspension concerns and before checking the wheel alignment.

Perform the following before measuring the trim heights

1. Set the tire pressures to the pressure shown on the certification label. Refer to «Label - Vehicle Certification, Tire Place Card, Anti-Theft and Service Parts ID»(/cadillac/sts/i-2004-2007/remont/hoistjack/#general-information) in General Information.
2. Check the fuel level. Add additional weight if necessary to simulate a full tank.
3. Make sure the rear compartment is empty except for the spare tire.
4. Make sure the vehicle is on a level surface, such as an alignment rack.
5. Close the doors.
6. Close the hood.
7. All dimensions are measured vertical to the ground. Trim heights should be within 13 mm (0.5 in) to be considered correct.

Z Height Measurement

The Z height dimension measurement determines the proper ride height for the front end of the vehicle. There is no adjustment procedure. Repair may require replacement of suspension components.

1. Lift the front bumper of the vehicle up about 38 mm (1.5 in).
2. Gently remove your hands. Let the vehicle settle.
3. Repeat this operation for a total of 3 times.
4. Measure from the pivot bolt center line down to the lower corner of the lower ball joint in order to obtain the Z height measurement.
5. Push the front bumper of the vehicle down about 38 mm (1.5 in).
6. Gently remove your hands.
7. Allow the vehicle to settle into position.
8. Repeat the jouncing operation 2 more times for a total of 3 times.
9. Measure the Z dimension.
10. The true Z height dimension number is the average of the high and the low measurements. Refer to «Trim Height Specifications»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__trim-height-specifications) .

D Height Measurement

The D height dimension measurement determines the proper rear end ride height. There is no adjustment procedure. Repair may require replacement of suspension components.

1. With the vehicle on a flat surface, lift upward on the rear bumper 38 mm (1.5 in).
2. Gently remove your hands. Allow the vehicle to settle into position.
3. Repeat the jouncing operation 2 more times for a total of 3 times.
4. Measure the D height by measuring the distance between the bumper bracket and the top of the rear axle tube.
5. Push the rear bumper downward to 38 mm (1.5 in).
6. Gently remove your hands. Allow the vehicle to settle into position.
7. Repeat the jouncing operation 2 more times for a total of 3 times.
8. Measure the D height dimension.
9. The true D height dimension number is the average of the high and the low measurements. Refer to «Trim Height Specifications»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__trim-height-specifications) .
10. If these measurements are out of specifications, inspect for the following conditions: Improper weight distribution Collision damage Worn or damaged suspension components

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 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 Inflation Pressure Specifications»(/cadillac/sts/i-2004-2007/remont/lubrication-system/#maintenance-and-lubrication__tire-inflation-pressure-specifications) in Maintenance and Lubrication and «Tire Diagnosis - Irregular or Premature Wear»(/cadillac/sts/i-2004-2007/remont/wheel-tire-system/#tires-and-wheels) in Tires and Wheels.
2. Inspect the runout of the wheels and the tires. Refer to «Tire and Wheel Runout Specifications»(/cadillac/sts/i-2004-2007/remont/oem-general-information/#vibration-symptoms-diagnosis-and-correction__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»(/cadillac/sts/i-2004-2007/remont/suspension-front/#suspension-general-diagnosis__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.
6. Inspect the steering gear for looseness at the frame. Refer to «Fastener Tightening Specifications»(/cadillac/sts/i-2004-2007/remont/manual-power-steering/#power-steering-system__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»(/cadillac/sts/i-2004-2007/remont/suspension-front/#suspension-general-diagnosis__struts-or-shock-absorbers-on-vehicle-testing) in Suspension General Diagnosis.
8. Inspect the vehicle trim height. Refer to «Trim Height Inspection Procedure»(/cadillac/sts/i-2004-2007/remont/suspension-front/#suspension-general-diagnosis) 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.
4. Adjust alignment angles to vehicle specification, if necessary. Refer to «Wheel Alignment Specifications»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__wheel-alignment-specifications) .

Tools Required

J 45845 Caster and Camber Adjusting Tool. See Special Tools .

1. Install J 45845 to the lower control arm and the frame. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__special-tools) .
2. Loosen the lower control arm to frame bolt.
3. Adjust the camber angle by turning the turnbuckle on J 45845 until the specifications have been met. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__special-tools) . Tighten: Tighten the bolt to 135 N.m (96 lb ft).
4. Verify that the camber is still with specifications. Refer to «Wheel Alignment Specifications»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__wheel-alignment-specifications) .
5. Adjust the rear toe. Refer to «Rear Toe Adjustment»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__rear-toe-adjustment) .

Front Toe Adjustment

1. Loosen the jam nut (1) on the outer tie rod.
2. Rotate the inner tie rod to the required toe specification setting. Refer to «Wheel Alignment Specifications»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__wheel-alignment-specifications) .
3. Tighten the jam nut to the outer tie rod. Tighten: Tighten the nut to 40 N.m (30 lb ft).
4. Check the toe setting after tightening. Refer to «Wheel Alignment Specifications»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__wheel-alignment-specifications) .
5. Re-adjust the toe setting if necessary.

J 45845 Caster and Camber Adjusting Tool. See Special Tools .

The caster and camber adjustments are made by loosening the lower control arm adjustment bolts and repositioning the lower control arm.

1. For an accurate reading, do not push or pull on the tires during the alignment process.
2. Determine the caster angle (2, 3).
3. Determine the camber angle (2, 3).
4. Install the J 45845 to the lower control arm and the frame. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__special-tools) .
5. Loosen the lower control arm adjustment nuts. NOTE: Refer to «Fastener Notice»(/cadillac/sts/i-2004-2007/remont/oem-general-information/#cautions-and-notices__fastener-notice) in Cautions and Notices.
6. Adjust the caster and the camber angle by repositioning the lower control arm until the specifications have been met. When the adjustments are complete, hold the lower control arm in position so that the specifications do not change while tightening the lower control arm adjustment bolts. Tighten: Tighten the lower control arm adjustment bolts to 135 N.m (96 lb ft).
7. Verify that the caster and the camber are still within specifications. Refer to «Wheel Alignment Specifications»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__wheel-alignment-specifications) . When the caster and camber are within specifications, adjust the toe. Refer to «Front Toe Adjustment»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__front-toe-adjustment) .

Rear Toe Adjustment

1. Loosen the adjustment link jam nuts (1).
2. In order to adjust the toe, rotate the turnbuckle (2).
3. Hold the turnbuckle (2) when tightening the jam nuts (1). Tighten: Tighten the jam nuts to 40 N.m (30 lb ft).
4. Recheck the toe setting after tightening.
5. Readjust the toe setting if necessary. Refer to «Wheel Alignment Specifications»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__wheel-alignment-specifications) .

Scheme 1

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.

Scheme 2

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 3

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.

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.

Scheme 4

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.

Lead/Pull Description

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/pull is usually caused by the following factors

1. Tire construction
2. Wheel alignment
3. Unbalanced steering gear

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

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.

Special Tools

Special Tools Illustration Tool Number/ Description J 45845 Caster and Camber Adjusting Tool

See also:
• Label - Vehicle Certification, Tire Place Card, Anti-Theft and Service Parts ID
• Radial Tire Lead/Pull Correction
• Tire Inflation Pressure Specifications
• Tire Diagnosis - Irregular or Premature Wear
• Tire and Wheel Runout Specifications
• Wheel Bearings Diagnosis
• Fastener Tightening Specifications
• Struts or Shock Absorbers On-Vehicle Testing
• Trim Height Inspection Procedure
• Fastener Notice
• Trim Height Specifications
• Wheel Alignment Specifications
• Special Tools
• Rear Toe Adjustment
• Trim Height Inspection Procedure
• Front Toe Adjustment