Wheel Alignment Measurement

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 vehicles 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 and adjustments in order to ensure correct alignment readings:
^ Inspect the tires for the proper inflation and irregular tire wear.
^ Inspect the runout of the wheels and the tires.
^ Inspect the wheel bearings for backlash and excessive play.
^ Inspect the ball joints and tie rod ends for looseness or wear.
^ Inspect the control arms and stabilizer shaft for looseness or wear.
^ Inspect the steering gear for looseness at the frame.
^ Inspect the struts/shock absorbers for wear, leaks, and any noticeable noises.
^ Inspect the vehicle trim height.
^ Inspect the steering wheel for excessive drag or poor return due to stiff or rusted linkage or suspension components.
^ 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.

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.




Front Caster and Camber Adjustment

1. Caster is relative to frame, the caster values must be compensated for the measured frame angle by using a digital protractor or equivalent on a flat portion of the frame in front of the rear tire.

Important: Caster measurements or values must be compensated for the measured frame angle.






2. Frame angle is positive when higher in the rear. Measure both sides of the frame and take an average from those measurements. Then add the average frame angle to the caster reading when making adjustments.





3. Frame angle is negative when lower in the rear. Measure both sides of the frame and take an average from the measurements. Then subtract the average frame angle from the caster reading when making adjustments.
4. The caster and camber adjustments are made by rotating the offset cam bolt and the cam in the slotted frame bracket in order to reposition the control arm.

Important: Before adjusting the caster and camber angles, jounce the front bumper three times to allow the vehicle to return to normal height.

Measure and adjust the caster and the camber with the vehicle at curb height. The front suspension Z dimension is indicated in Trim Heights. Refer to Trim Height Inspection Procedure in Suspension General Diagnosis.
For an accurate reading, do not push or pull on the tires during the alignment process.





5. Determine the caster angle (2). Be sure to compensate for frame angle where required.





6. Determine the positive camber (2) or negative camber (3) angle.
7. Remove the pinned adjusting cam insert. Do not reinstall the cam insert.
8. Loosen the upper control arm cam adjustment bolts.

Notice: Refer to Fastener Notice in Service Precautions.





9. Adjust the caster and the camber angle by turning the cam bolts until the specifications have been met. When the adjustments are complete, hold the cam bolt head in order to ensure the cam bolt position does not change while tightening the nut.
^ Tighten the cam nuts to 190 Nm (140 ft. lbs.).
10. Verify that the caster and the camber are still within specifications. Refer to Wheel Alignment Specifications. When the caster and camber are within specifications, adjust the toe. Refer to Front Toe Adjustment.



Front Toe Adjustment





1. Loosen the jam nut on the tie rod (2).
2. Rotate the inner tie rod (1) to the required toe specification setting. Refer to Wheel Alignment Specifications.

3. Tighten the jam nut on the tie rod.
^ Tighten the tie rod jam to 68 Nm (50 ft. lbs.).

Notice: Refer to Fastener Notice in Service Precautions.

4. Check the toe setting after tightening.
5. Re-adjust the toe setting if necessary.



Rear Toe Adjustment





1. Loosen the jam nut on the tie rod (1).
2. Rotate the inner tie rod to the required toe specification setting. Refer to Wheel Alignment Specifications.

3. Tighten the jam nut on the tie rod.
^ Tighten the tie rod jam to 65 Nm (48 ft. lbs.).

Notice: Refer to Fastener Notice in Service Precautions.

4. Check the toe setting after tightening.
5. Re-adjust the toe setting if necessary.