ASE · Suspension and Steering (A4) · 7 min read
Wheel Alignment Diagnosis and Adjustment
- Identify pre-alignment inspection requirements, ride-height effects, and mechanical conditions that must be corrected prior to performing alignment adjustments.
- Diagnose handling concerns, steering symptoms, and abnormal tire wear patterns using primary and secondary alignment angles.
- Apply correct adjustment procedures, frame-referencing methods, and electronic steering and driver-assist system calibrations according to manufacturer service information.
Pre-Alignment Inspection and Suspension Ride Height
A proper wheel alignment begins before the vehicle is ever placed on an alignment rack. Technicians must first perform a thorough physical inspection of the suspension, steering, and tires. Checking and correcting curb ride height according to manufacturer specifications is required before measuring or adjusting wheel alignment angles. Sagging springs can change ride height and, depending on suspension design, change one or more alignment angles; measure ride height under the manufacturer's specified conditions before final adjustment. A heavily loaded or sagging rear suspension changes vehicle pitch and can affect measured front alignment angles or handling; check ride height under the manufacturer's specified loading conditions before diagnosing the cause. If ride height is outside specification, diagnose and correct its cause, which may include loading, springs, or damaged components, before adjusting alignment angles.
Tire condition and inflation pressures are equally vital during the initial evaluation. Unequal tire pressures or mismatched tire rolling diameters can cause a vehicle pull even when alignment angles match specification. In addition, worn suspension ball joints, loose tie-rod ends, and excessive wheel bearing play must be repaired before performing an alignment. Measure suspected steering, suspension, and wheel-bearing play against manufacturer limits, and correct excessive play before making final alignment adjustments.
Finally, inspect the vehicle structural mounting points and chassis condition. Damaged or collapsed component mounting points must be repaired to manufacturer body dimensions before wheel alignment angles can be corrected. Manufacturer service information is the final authority for all pre-alignment inspection procedures, ride-height measuring locations, and vehicle tolerances.
Common mistakes
- Adjusting one tie rod without verifying individual toe, total toe, and steering-wheel centering can leave the steering wheel crooked; follow the manufacturer's procedure and adjust whichever tie rod or rods are needed.
- Attempting to correct a pull or abnormal tire wear by performing an alignment on a vehicle with uncorrected, sagging curb ride height or mismatched tire rolling diameters.
- Replacing a crossmember or subframe solely because included angle is incorrect, without verifying the readings and identifying the damaged or mispositioned component.
- Omitting an SAS reset or EPS relearn when manufacturer service information requires one after alignment or steering work can contribute to ESC or steering-assist complaints.
Key points
- Curb ride height must be measured and restored to manufacturer specification before alignment, as sagging springs alter camber, caster, and toe.
- Cross-camber tends to pull toward the side with more positive camber, and cross-caster tends to pull toward the side with less positive caster; excessive camber can cause shoulder wear, while caster does not directly cause tread wear.
- Incorrect toe commonly causes rapid scrub and feathering; follow the manufacturer's steering-wheel-centering procedure and adjust one or both tie rods as needed to bring individual and total toe into specification.
- Included angle is the sum of SAI and camber; after verifying the readings, an incorrect included angle calls for inspection of the knuckle, strut, applicable adjustments, and related parts, while opposite SAI and camber changes with a correct included angle call for inspection of suspension and mounting-point positions.
- A four-wheel alignment measures rear thrust angle and uses the appropriate rear reference when setting front alignment; correcting excessive rear thrust angle or dog-tracking requires diagnosing and correcting the rear alignment or damaged components, not merely adjusting front toe.
- Specific handling faults indicate mechanical binding or geometry mismatches: wander (insufficient caster/loose linkage), memory steer (binding joints/bearings), bump steer (mismatched linkage geometry), and torque steer (cradle misalignment/half-shaft angles).
- Modern alignments require checking manufacturer service information for mandatory electronic resets, including Steering Angle Sensor (SAS) calibration, EPS compensation relearns, and ADAS calibrations.
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