Alignment: Testing and Inspection

Trim Height Inspection

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 suspension components, and symptoms similar to wheel alignment problems. Inspect the trim heights when diagnosing suspension concerns and before inspecting the wheel alignment.

Perform the following prior to measuring trim heights:

* Make sure the vehicle is on a level surface, such as an alignment rack.
* Set the tire pressures to specifications. Refer to Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label (Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label).
* Check the fuel level. Add additional weight if necessary to simulate a full tank.
* Inspect for aftermarket equipment that may add weight to the vehicle.
* To ensure proper weight distribution, make sure the rear storage compartment is empty.
* Close the doors and hood.

Z Height Measurement

The Z height measurement determines the proper ride height for the front end of the vehicle. Vehicles equipped with torsion bars use an adjusting arm to adjust the Z height. Vehicles without torsion bars have no adjustment and may require replacement of suspension components.

Important: All dimensions are measured vertical to the ground. Cross vehicle Z heights should be within 24 mm (0.9 in).


1. Place hands on the front bumper and jounce the front of the vehicle. Make sure that there is at least 38 mm (1.5 in) of movement while jouncing.
2. Allow the vehicle to settle into position.




3. Measure from the centerline (1) of the lower control arm bushing bolt (4) down to the machined edge of the steering knuckle (2) in order to obtain Z height measurement (3).
4. Repeat the jouncing operation and measurement 2 more times for a total of 3 times.
5. Use the highest and lowest measurements to calculate the average height.
6. The true Z height dimension number is the average of the high and the low measurements. Refer to Trim Height Specifications (Trim Height Specifications).
7. If these measurements are out of specifications, inspect for the following conditions:

* Sagging front suspension-Refer to Shock Absorber and Spring Assembly Replacement (Shock Absorber and Spring Assembly Replacement).
* Collision damage

D Height Measurement

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

Important: All dimensions are measured vertical to the ground. Cross vehicle D heights should be within 12 mm (0.5 in) for vehicles equipped with coil springs. Vehicles equipped with air suspension should be within 8 mm (0.3 in).


1. Place hands on the rear bumper and jounce the rear of the vehicle. Make sure that there is at least 38 mm (1.5 in) of movement while jouncing.
2. Allow the vehicle to settle into position.





Important: A D-height block can be used to determine the D-height position. Create a D-height measurement gage, using metal stock. Cut a block to 20 mm (0.79 in) X 30 mm (1.81 in) X the correct D trim height specification. For the correct D height specification, refer to Trim Height Specifications (Trim Height Specifications).


3. Measure the D height by measuring vertical distance (2) between the top surface of the axle and to the side of the hole, center on the jounce bumper reinforcement bracket.
4. Repeat the jouncing operation and measurement 2 more times for a total of 3 times.
5. Use the highest and lowest measurements to calculate the average height.
6. The true D height dimension is the average of the highest and lowest measurements. Refer to Trim Height Specifications (Trim Height Specifications).
7. If these measurements are out of specifications, inspect for the following conditions:

* Sagging rear suspension-Refer to Coil Spring Replacement (Rear Suspension) , Air Suspension Description and Operation (Description and Operation) or Trim Height Uneven or Low (Trim Height Uneven or Low).
* Collision damage