Chevrolet Trax: Trim height inspection

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 .

NOTE: One U.S. gallon of gasoline weighs approximately 6.5 lbs. One liter of gasoline weighs approximately 0.7 kg.

• Check the fuel level. Add additional weight if necessary to simulate a full tank.
• Make sure the passenger and rear compartments are empty, except for 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 installed after market accessories or modifications that could affect trim height measurement:

• Larger or smaller than production wheels and tires.
• Lifting or Lowering Kits
• Wheel Opening Flares or Ground Effects

Measuring the P and R Dimension

Fig. 1: Measuring P And R Dimension

Measurement Definitions

P Height: The vertical distance from the center of the front wheel to the top of the wheel opening.

R Height: The vertical distance from the center of the rear wheel to the top of the wheel opening.

Use the following procedures to measure the P and R dimensions:

NOTE:

• Measure from the center of the wheel well opening to the ground.
• The left and right P and R height differences should be no more than 15 mm (0.60 in).

1. Push the front bumper down a minimum of 38 mm (1.59 in) and release. Perform this step three times.
2. Measure and record the trim height per the "Measurement Definitions" above.
3. Lift the bumper up a minimum of 38 mm (1.59 in) and release. Perform this step three times.
4. Measure and record the trim height per the "Measurement Definitions" above.
5. The true P height measurement is the average of the measurements taken in step 2 and 4. Refer to Trim Height Specifications (USA), Trim Height Specifications (Canada)
6. Repeat the above steps at the rear of the vehicle for the R heights.

Measuring the Z Dimension

Fig. 2: Measuring Z Dimension

Measurement Definition

The Z Height: The vertical distance from the center of the ball joint cup (1) to the bottom of cradle, center of lower control arm rear bushing mount (2).

The Z Height dimension measurement determines the proper ride height for the front end of the vehicle. There is no adjustment procedure. Repair may require replacement of suspension parts.

Use the following procedures to check the Z height dimension:

1. Using your hands, lift the front bumper approximately 38 mm (1.59 in).
2. Gently remove your hands and allow the vehicle to settle.
3. Repeat the jouncing operation a total of 3 times.
4. Measure the vertical distance from the center of ball joint cup to the bottom of cradle, center of lower control arm rear bushing mount.
5. Using your hands, jounce the front of the vehicle downward approximately 38 mm (1.59 in).
6. Gently remove your hands and allow the vehicle to settle.
7. Repeat the jouncing operation a total of 3 times.
8. Measure the Z height dimension.
9. The true Z height dimension number is the average of the high and the low measurements. Refer to Trim Height Specifications (USA), Trim Height Specifications (Canada).

Measuring the D Dimension

Fig. 3: Measuring D Dimension

Measurement Definition

The D Height: The vertical distance from the bolt head center of rear shock absorber lower attachment (1) to the bottom surface of underbody side rail (2), vertically above the shock bolt head.

The D Height dimension measurement determines the proper rear end ride height. There is no adjustment procedure. Repair may require replacement of suspension parts.

Use the following procedure to check the D height dimension:

1. With the vehicle on a flat surface, lift upward on the rear bumper 38 mm (1.59 in).
2. Gently remove your hands and allow the vehicle to settle.
3. Repeat the jouncing operation 2 more times.
4. Measure the vertical distance from the bolt head center of rear shock absorber lower attachment to the bottom surface of underbody side rail, vertically above the shock bolt head.
5. Repeat this task for the other side of the vehicle.
6. Using your hands, jounce the front of the vehicle downward approximately 38 mm (1.59 in).
7. Gently remove your hands and allow the vehicle to settle.
8. Repeat the jouncing operation 2 more times.
9. Measure the D height dimension.
10. The true D height dimension number is the average of the high and the low measurements. Refer to Trim Height Specifications (USA), Trim Height Specifications (Canada).
11. If these measurements are out of specifications, inspect for the following conditions:

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