Severe-Duty Vocational Rear Air Suspension System

PRIMAAX EX Air Suspension System

With its rugged, weight efficient design, PRIMAAX® EX is a severe-duty vocational rear air suspension that delivers advanced suspension technology for the rigorous demands of vocational, severe-service, and heavy-haul applications. The system features a robust structural design with optimized suspension geometry for exceptional stability, handling and ride. Suspension-induced driveline vibration is significantly reduced with PRIMAAX EX compared to competitive trailing-arm air suspensions, resulting in higher driver comfort and less premature wear on expensive truck and body equipment.

PRIMAAX EX Air Suspension System

Features and Benefits

  • Advanced structural beams utilize premium materials for high durability and reliability
  • Robust frame hangers enhance system durability to meet a variety of grueling vocational and severe-duty applications
  • Optimized suspension geometry contributes up to twice the roll stability of competitive air suspensions, helps improve handling and roll stiffness for expanded applications and significantly controls suspension-induced driveline vibration
  • Structural beams include integrated end caps that form a solid connection with the square cross brace to form a rigid torsion system for improved stability and control
  • Superior off-road mobility with up to 12.5 inches of diagonal wheel travel and 8 inches of vertical axle travel
  • Large-volume air springs lift and support the load with less air pressure, while providing superb ride quality
  • Premium, heavy-duty bushings require no lubrication for reduced maintenance
  • QUIK-ALIGN® system helps simplify axle alignment for reduced maintenance time and extended tire life


Model PRIMAAX EX          
Capacity (lbs) 23,000 26,000 46,000 52,000 69,000 78,000
Installed Weight1 (lbs) 542 651 1,078 1,292 1,629 1,931
Axle Configuration Single Single Tandem Tandem Tridem Tridem
GCW Approval2 (lbs) Contact vehicle OEM2 Contact vehicle OEM2 Contact vehicle OEM2 Contact vehicle OEM2 Contact vehicle OEM2 Contact vehicle OEM2
Site Travel Rating3 (lbs) 30,000 33,000 60,000 66,000 90,000 99,000
Axle Travel4 (in) 8 8 8 8 8 8
Ground Clearance (in) 10.75 10.5 10.75 10.5 10.75 10.5
Lift Axles Approved Approved Approved Approved Approved Approved
Ride Heights5 (in) 8.5 to 10.5
12.5 to 15.5
8.5 to 10.5
12.5 to 15.5
8.5 to 10.5
12.5 to 15.5
8.5 to 10.5
12.5 to 15.5
8.5 to 10.5
12.5 to 15.5
8.5 to 10.5
12.5 to 15.5
Engine Torque Restrictions None None None None None None
Axle Spacing (in) N/A N/A 52 to 72.5 54 to 72.5 52 to 60 54 to 60
  • PRIMAAX® EX is approved for vocational and heavy-haul vehicle applications including, but not limited to: truck, tractor, dump, front and rear discharge mixer, logging, crane mounted, platform, fire / rescue, specialty and vehicles equipped with outriggers. All applications must comply with applicable Hendrickson specifications and must also be approved by the respective vehicle manufacturer with the vehicle in its original, as-built configuration. Contact Hendrickson and the respective vehicle manufacturer for approval of additional applications.
  • For additional details regarding specifications, applications, capacities, and operating, service and maintenance instructions, refer to applicable Hendrickson technical literature or contact Hendrickson at 630-910-2800.

1. Installed weight includes complete suspension, torque rods, axle and frame brackets and all hardware. Published weight is for standard PRIMAAX EX suspension using 10.0-inch ride height. Other configurations may change weight.

2. Suspension must be paired with appropriate axle rating.

3. Site Travel Rating — Operators using vehicles equipped with liftable push or tag axles must not exceed published ratings. Ratings are limited to no more than five percent of vehicle operation at a speed not to exceed five mph. Liftable pusher or tag axles should be raised (or unloaded) to improve vehicle maneuverability in off-road use or when vehicle is empty. Site travel ratings are consistent with specifications and must not be exceeded.

4. Axle travel may be limited by vehicle manufacturer; axle stop settings and shock stroke may restrict suspension's articulation. Varying ride heights and configurations may restrict travel.

5. For different ride height options, please contact Hendrickson, your truck manufacturer or dealer for further information.

6. Refer to axle manufacturer's recommendation.


File Name Rev. Date Size
Hendrickson Academy

Service Academy

A Hendrickson service education portal to gain a greater knowledge on how to service Hendrickson products.  Register to start learning today.

Earn Certificate
Extended Warranty Page

Truck Extended Warranty

Available to purchase up to one year after the vehicle is placed in service. Stay at ease knowing any applicable repairs will not create unexpected out-of-pocket costs.

Upgrade Warranty

Weight Savings Calculator

Calculate your weights saving by using our easy to use tool.

Calculate savings

Need Help? Call 1-855-RIDE-RED or Contact Us