List of Peterbilt Flex Air Suspension Issues (+5 Main Types)

In this brief article we are going to discuss the different  Peterbilt Flex Air Suspension problems, what the causes are, and Troubleshooting Tips.

What are the most common  Peterbilt Flex Air Suspension issues? 

The most common  Peterbilt Flex Air Suspension issues are:

  • Rough Ride at rear
  • Tyre Scrubbing

Peterbilt Flex Air Suspensions

The ‘Kenworth AirGlide 380’ air suspension system by Kenworth is Branded as the ‘Peterbilt Flex Air’ Suspension, when used on the Peterbilt truck. It is identifiable by its unique ‘C-Shaped Spring Link’.

Different Types of Peterbilt Truck Air Suspension

  • Air Trac
  • Air Leaf with Tracking Rods
  • Low and Low-Low Air Leaf Tandem (built April 2004 or later) and Flex Air
  • Low and Low-Low Air Leaf Tandem (built prior to April 2004)
  • Low Air Leaf Single

Rough Ride at the rear in Flex Air

  • Rear suspension ride feels rough
  • Rear gets unsettled going over bumps
  • The rear instability could be due to either
    • Air Suspension Pressure loss or leakage
    • Shock Absorber issues
    • Suspension Joints
    • Axle U-Bolt Tightening
  • Check if the rear suspension ride height is satisfactory. Verify if the rear air bags can be raised or lowered. This is to see if the compressor has issues with generating pressure
  • Check, with a pressure gauge whether the air compressor produces the required pressure
  • Also see if the load sensing valve is functioning properly
  • Inspect the shock absorbers for any oil stains near the Rod seal
  • The axle U-Bolts tend to loosen if not checked regularly. Use a digital Torque wrench to verify the residual torques.

Tyre Scrubbing

  • Uneven Tyre wear on the wheels
  • The reason this happens is due to the tires missing their alignment 
  • The best way to deal with  it is to get the alignment done at a place that does alignment for Trucks. Car and Van alignment shops might not be able to do a good job.
  • If an alignment did not solve the issue, then it might be the case that the axles are bent. 
  • In order to check axle bened, you can use a straight edge plank or a sheet-metal channel of roughly 1-2 mtr and place it over the edges of both the tyres on the sidewall.
  • Ideally, there must be no gap between the tires and the plank. If there is a gap, then it means that there is an issue with either of the axles
  • Also check the center distance between the axles on both sides. Use the in-built adjustment to align the axles back to the manufacturer recommendations.


In this brief article we have discussed the different Peterbilt Flex Air Suspension problems, what the causes are, and Troubleshooting Tips.