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PRIMAAX^® EX

Severe-duty vocational rear 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.

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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

Specifications

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.

Literature

File Name	Rev.	Date	Size


Sales Brochures

45745-178 PRIMAAX EX Brochure	T	4/9/2025	0.57 MB
45745-178FR PRIMAAX EX Brochure	R	11/13/2024	1.31 MB
45745-228 PRIMAAX EX - Freightliner Sell Sheet	F	5/5/2020	0.32 MB
45745-244 PRIMAAX EX Sell Sheet for Volvo	B	7/1/2011	0.52 MB
45745-250 PRIMAAX EX Sell Sheet for Kenworth	I	1/30/2024	0.54 MB
45745-317 PRIMAAX Tridem Sell Sheet	B	5/12/2014	0.52 MB
45745-374 PRIMAAX EX Defense Brochure	F	5/24/2023	0.51 MB
45745-104 Vocational Suspension Application Summary	Q	4/10/2025	0.53 MB
45745-219 PRIMAAX / COMPOSILITE SC for Front Discharge Mixers	F	4/25/2023	0.99 MB
45745-352 Defense Suspension Product Line	H	1/21/2025	0.78 MB
45745-377 PRIMAAX EX for International	D	9/24/2024	0.51 MB
45745-403 Army Heavy Dump Truck Suspension	B	8/21/2019	0.56 MB
45745-559 PRIMAAX EX for Sewer Pumper / Wastewater / HCG Trucks	C	1/22/2025	0.16 MB
INTL160 - EV Severe-Duty Solutions	B	3/28/2024	0.28 MB
45745-541 - PRIMAAX EX for Peterbilt flyer	B	6/2/2023	0.57 MB
45745-596 - PRIMAAX EX for Mack	A	6/21/2024	0.51 MB
Parts Lists

45745-148 Torque Rod Selection Guide	G	1/31/2025	2.13 MB
SP-164 PRIMAAX EX and PRIMAAX Parts List (Replaces SP-225)	O	6/17/2024	5.99 MB
SP-226 PRIMAAX EX Parts List for Volvo Vehicles	G	1/3/2024	0.94 MB
SP-230 PRIMAAX EX Parts List for Freightliner and Western Star	D	5/21/2024	1.48 MB
SP-231 PRIMAAX EX / PRIMAAX Parts List for Mack	G	1/3/2024	0.94 MB
SP-233 PRIMAAX EX / PRIMAAX Parts List for International Truck	E	5/30/2024	2.99 MB
SP-234 PRIMAAX EX Parts List for Caterpillar	D	8/8/2023	1.43 MB
SP-329 PRIMAAX EX Rear Suspension Parts List for Mack Heavy Dump Truck (HDT) Vehicles	B	8/23/2024	1.72 MB
Tech Bulletins

SEU-0229 PRIMAAX / FIREMAAX Support Beam Discontinuance	C	2/1/2014	0.18 MB
SEU-0233 PRIMAAX EX / FIREMAAX EX U-beam Assembly Enhancement	C	3/14/2022	0.17 MB
12463-044 PRIMAAX EX Small Clamp Group vs Large Clamp Group Tech Tip	A	10/11/2024	1.22 MB
12463-044SP PRIMAAX EX Paquete de Sujeción Pequeño vs. Paquete de Sujeción Grande	A	10/22/2024	4.93 MB
Service Guides/Manuals

17730-238 PRIMAAX EX Technical Procedure	H	5/16/2024	6.41 MB
17730-254 PRIMAAX EX Technical Procedure for Volvo	E	12/20/2023	4.12 MB
17730-263 PRIMAAX EX Technical Procedure for Kenworth Vehicles	G	12/23/2021	6.55 MB
17730-266 PRIMAAX EX /FIREMAAX EX Preventive Maintenance	D	3/15/2021	0.63 MB
17730-279 PRIMAAX EX Technical Procedure for Mack Vehicles	C	12/21/2023	4.12 MB
17730-283 PRIMAAX EX Technical Procedure for International Truck Technical Procedure	A	6/1/2012	4.24 MB
17730-284 PRIMAAX EX for Caterpillar Tech Procedure	A	6/1/2012	3.68 MB
17730-329 PRIMAAX EX Tridem Rear Suspension Tech Procedure for Mack Heavy Dump Truck (HDT) Vehicles	B	2/3/2025	5.77 MB
59310-035 PRIMAAX Ass'y Inst. Severe Service Air Spring	A	9/1/2007	0.15 MB
59310-036 PRIMAAX Ass'y Inst. Severe Service Top Pad Bolt	A	10/1/2007	0.1 MB
59310-060 PRIMAAX EX Aftermarket Shock Absorber for Mexico, Central and South America Assembly Inst.	A	10/1/2013	0.12 MB
59310-037 PRIMAAX EX · FIREMAAX EX Severe-duty Bushing and QUIK-ALIGN Kits	B	11/1/2020	0.3 MB
59310-061 QUIK-ALIGN Pivot Bushing Tool 66086-203L for PRIMAAX EX · FIREMAAX EX	C	2/22/2023	0.64 MB
12463-039 PRIMAAX EX QUIK-ALIGN Tech Tips	B	2/22/2023	1.43 MB
12463-037 QUIK-ALIGN Pivot Bushing Tech Tips	A	7/5/2014	0.59 MB

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PRIMAAX^® EX

Severe-duty vocational rear air suspension system

Features and Benefits

Specifications

Literature

Sales Brochures

Parts Lists

Tech Bulletins

Service Guides/Manuals

Service Academy

Truck Extended Warranty

Weight Savings Calculator

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