Ride quality is subject to many influences in heavy-duty applications. They include, but are not limited to, body equipment, rear suspension, cab suspension, terrain, chassis/frame specifications, tires/wheels, front suspension and wheelbase.

Most production vehicles are equipped with the standard production assembly, using a three spacer shim system (1). A small percentage of select vehicles will require a shim system other than the standard production assembly.

View the matrix below and check if your vehicle falls under one of the following applications and is within the unladen tandem axle weight ranges (with all equipment/truck bodies installed.

If so, these applications require optimum ride quality and also a very high level loaded stability. Install or remove shims in order to reach the recommended number of total shims per beam as stated below.

Important: Both sides of the HAULMAAX® suspension must have an equal number of shims in place.

Applications where stability is more important than ride quality, install additional shims onto each beam to reach the recommended shims (maximum of 5) per beam.

For removal and installation of the shim spacers after determining the proper amount required, refer to Rear Auxiliary Spring Shim Replacement.