GM Service Manual Online
For 1990-2009 cars only

Incorrect trim heights can cause bottoming out over bumps. Incorrect trim heights can cause possible damage to the suspension components and symptoms similar to those produced when there is a problem with the wheel alignment. Check the trim heights when diagnosing suspension complaints and before checking the wheel alignment.

Perform the following steps before measuring the trim height:

  1. Ensure that the fuel tank is full.
  2. Ensure that the correct size tires are on the vehicle.
  3. Set the tire pressures to the pressure shown on the tire placard. The tire placard is located on the driver's door.
  4. Make sure the vehicle is on a level surface, such as an alignment rack.
  5. Close the doors.
  6. Close the hood.
  7. Close the trunk lid.

Important: All trim height measurements are taken vertical to the ground. Trim height measurements within 6 mm (0.24 in) are considered correct.

Measuring J and K Dimensions


Object Number: 186760  Size: MH
  1. Use your hands in order to lift the front bumper of the vehicle up approximately 38 mm (1.5 in). Gently remove your hands in order to allow the vehicle to lower.
  2. Use your hands in order to push the front bumper of the vehicle down approximately 38 mm (1.5 in). Remove your hands in order to allow the vehicle to rise.
  3. Measure the J dimension for the left and right side of the vehicle 605 mm (23.8 in) from the centerline of the FRONT wheel.
  4. Replace the front springs to correct the front trim height as necessary.
  5. Use your hands in order to lift the rear bumper of the vehicle up approximately 38 mm (1.5 in). Gently remove your hands in order to allow the vehicle to lower.
  6. Use your hands in order to push the front bumper of the vehicle down approximately 38 mm (1.5 in). Remove your hands in order to allow the vehicle to rise.
  7. Measure the K dimension for the left and right side of the vehicle 525 mm (20.7 in) from the centerline of the REAR wheel.
  8. Replace the rear springs to correct the rear trim height as necessary.

Measuring Z and D Dimensions


    Object Number: 186754  Size: SH
  1. Use your hands in order to lift the front bumper of the vehicle up approximately 38 mm (1.5 in). Gently remove your hands in order to allow the vehicle to lower.
  2. Use your hands in order to push the front bumper of the vehicle down approximately 38 mm (1.5 in). Remove your hands in order to allow the vehicle to rise.
  3. Measure the Z dimension for the left and right side of the vehicle. The Z dimension is the vertical distance measured between the center of the rear bushing bolt (1) and the lowest inboard point on the ball joint (2).
  4. Replace the front springs to correct the front trim height as necessary.

  5. Object Number: 236112  Size: SH
  6. Use your hands in order to lift the rear bumper of the vehicle up approximately 38 mm (1.5 in). Gently remove your hands in order to allow the vehicle to lower.
  7. Use your hands in order to push the front bumper of the vehicle down approximately 38 mm (1.5 in). Remove your hands in order to allow the vehicle to rise.
  8. Measure the D dimension for the left and right side of the vehicle. The D height is measured from a point 30 mm outboard of the rear brake hose bracket bolt centerline to the bolt centerline of the trailing arm to the knuckle attachment.
  9. Replace the rear springs to correct the rear trim height as necessary.