The following steps are recommended by SAF-HOLLAND for properly measuring the ride height on trucks/tractors equipped with drive axle air suspensions. We recommend that you follow your specific height control valve manufacturer’s instructions for ride height adjustment procedures, and follow the suspension and vehicle manufacturers’ maintenance manual instructions for safety and proper practice.
To check the current ride height of your suspension, use the following steps:
1. Determine the vehicle manufacturer’s correct suspension ride height for your vehicle. Determine which axle the height control valve is attached to on multi-axle vehicles.
2. Drive the vehicle forward in a straight line for at least two (2) vehicle lengths to release any bushing wind up.
3. With the vehicle unloaded and/or trailer disconnected on a level surface, chock the front tires to prevent the vehicle from rolling forward or backward.
4. Pressurize the air system with a constant supply of air in excess of 70 psig (4.8 bars), and check that all air springs properly inflate and raise the suspension to the proper ride height.
5. On the axle where the height control valve is attached, measure the distance from the bottom of the frame rail to the ground.
6. Measure the distance from the center of the wheel to the ground.
7. Subtract the measurement found in Step 6 from the measurement found in Step 5 to determine the current ride height of your suspension.
- Example: The bottom of the frame rail to the ground measures 30" (762 mm) and the center of the wheel to the ground measures 20" (508 mm). Subtract the second measurement (20") from the first measurement (30") and this equals 10" (254 mm) for current Ride Height (30" – 20" = 10")
- Check the value against the specification in Step 1.
IMPORTANT: If the measured ride height is not within ± .25" (6 mm), it must be adjusted using the height control valve. Refer to the height control valve manufacturer’s instructions for adjustment procedures of that equipment and use the suspension and vehicle manufacturers’ maintenance manual instructions for the proper procedure for making adjustments. These sources of information typically contain diagnostic measures to follow to troubleshoot cause and effect of problems.
Information provided by: SAF-HOLLAND
