GM Service Manual Online
For 1990-2009 cars only

Trim Height Measurement

Trim height is a predetermined measurement relating to vehicle ride height. Incorrect trim heights can cause the vehicle to bottom 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:

    • Set the tire pressure to the specifications shown on the certification label. Refer to 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.
    • Make sure the passenger and rear compartments are empty except tor the spare tire.
    • Make sure the vehicle is on a flat and level surface such as an alignment rack.
    • Check that all the vehicle doors are securely closed.
    • Check that the vehicle hood and rear deck lids are securely closed.
    • Check for after market accessories or modifications that could affect trim height measurement.

Z Height Measurement

Use the following procedure to check the Z dimension:

  1. Lift the rear bumper of the vehicle up about 38 mm (1.5 in).
  2. Gently remove your hands and let the vehicle settle.
  3. Repeat this operation 2 more times for a total of 3.

  4. Object Number: 2019031  Size: SH
  5. Z height is measured vertically from the rear axle centre point to the bottom lip of the wheel opening.
  6. Push the rear bumper of the vehicle down about 38 mm (1.5 in).
  7. Gently remove your hands and let the vehicle settle down.
  8. Repeat this operation 2 more times for a total of 3.
  9. Measure the Z height as in step 4.
  10. The true Z height measurement is the average of the measurements taken in step 4 and 8. Refer to Trim Height Specifications for correct value.