Hendrickson HAULMAAX EX

Quick Facts

Manufacturer: Hendrickson
Product Name: HAULMAAX EX
Suspension Type: Heavy-duty rear rubber suspension
Primary Configuration: Tandem rear-drive axle suspension
Available Suspension Ratings: 40,000, 46,000, and 52,000 pounds
Loaded Ride Heights: Approximately 8 to 18.5 inches, depending on configuration
Diagonal Articulation: Up to 17 inches
Available Axle Spacings: Approximately 52 to 72.5 inches, depending on model
Spring Design: Rubber bolster springs with progressive load springs
Common Applications: Dump, concrete mixer, refuse, logging, crane or boom, platform, and fire or rescue vehicles
Lift-Axle Compatibility: Approved when properly specified and operated within published limits
Shock Absorbers: Required for tractor and logging applications and optional for certain other applications
Current Models: HAULMAAX EX 400, HAULMAAX EX 460, and HAULMAAX EX 520

Overview

The Hendrickson HAULMAAX EX is a heavy-duty rear rubber suspension designed for vocational trucks operating under demanding on-road and job-site conditions. It combines equalizing beams, rubber bolster springs, progressive load springs, torque rods, and bar-pin axle connections to provide load support, stability, articulation, and axle control without using air springs or conventional steel spring packs.

HAULMAAX EX is intended to balance unloaded ride quality with loaded stability. Its progressive spring system becomes firmer as vehicle weight increases, while the equalizing beams help distribute loads between the tandem drive axles.

Hendrickson offers the suspension in 40,000-, 46,000-, and 52,000-pound ratings. The system is commonly specified for dump trucks, concrete mixers, refuse trucks, logging equipment, crane and boom vehicles, platform trucks, and fire or rescue apparatus.

Key Characteristics

Heavy-duty rubber suspension designed for vocational rear-drive axles
Available in 40,000-, 46,000-, and 52,000-pound suspension ratings
Rubber bolster springs support most of the vehicle load
Progressive load springs increase suspension stiffness as weight increases
Equalizing beams distribute weight between the tandem axles
Up to 17 inches of diagonal articulation
Eliminates the fixed center bushings found in many traditional walking-beam suspensions
Bar-pin end connections provide axle attachment and alignment capability
Longitudinal torque rods resist axle windup during acceleration and braking
Transverse torque rods control lateral axle movement
Optional shock absorbers improve damping and driver comfort
Shock absorbers are required for tractor and logging applications
Available in several ride heights and axle spacings
Compatible with approved lift-axle configurations
Designed to reduce suspension weight compared with many traditional severe-duty mechanical suspensions

Major Components

Equalizing Beams

The formed and robotically welded equalizing beams connect the tandem drive axles and help distribute vehicle weight between them. Their narrow profile supports component clearance and helps reduce suspension weight.

Rubber Bolster Springs

Angled rubber bolster springs carry most of the vehicle and payload weight. Their placement helps the suspension resist braking, acceleration, and cornering forces while allowing controlled movement.

Progressive Load Springs

The progressive load springs increase stiffness as the load increases. This helps provide a more compliant response when the vehicle is empty while improving stability when fully loaded.

Frame Saddles and Brackets

Frame saddles and mounting brackets connect the suspension to the truck frame. Their configuration must match the chassis width, ride height, beam length, axle spacing, and vehicle application.

Bar-Pin End Bushings

Bar-pin end bushings connect the equalizing beams to the axle brackets. These connections help control axle position and provide the adjustment points used for drive-axle alignment.

Longitudinal Torque Rods

Longitudinal torque rods help control axle rotation and maintain pinion-angle relationships during acceleration and braking.

Transverse Torque Rods

Transverse torque rods control side-to-side axle movement and help maintain lateral alignment beneath the chassis.

Rebound Straps

Rebound straps limit suspension extension and help protect the rubber bolster springs. Dual rebound straps are standard on the 52,000-pound version and are required on vehicles equipped with outriggers.

Shock Absorbers

Shock absorbers control suspension movement and improve damping. They are required in tractor and logging applications and may be added to other approved configurations.

How the Suspension System Works

HAULMAAX EX uses rubber springs and equalizing beams instead of air bags or conventional steel leaf-spring packs.

The rubber bolster springs carry most of the vehicle’s weight. As the load increases, the progressive load springs engage more firmly and increase suspension stiffness. This provides a balance between unloaded ride quality and loaded roll stability.

The equalizing beams transfer and distribute weight between the tandem drive axles. When one axle moves upward over an obstacle, the beam system allows the opposite axle to respond, helping the tires remain in contact with uneven ground.

Longitudinal torque rods limit axle windup caused by engine torque and braking forces. Transverse torque rods restrict lateral axle movement during cornering and operation on uneven surfaces.

Because the system does not depend on compressed air, it does not require air springs, suspension height-control valves, or air-line plumbing to support the vehicle.

Suspension Position and Function

HAULMAAX EX is installed beneath the rear frame of a vocational truck or tractor and supports a tandem-drive axle group.

Its primary functions include:

Supporting the rear portion of the chassis and payload
Distributing weight between the tandem drive axles
Allowing the axles to articulate over uneven surfaces
Controlling axle movement during acceleration and braking
Maintaining lateral axle position beneath the frame
Helping keep the drive tires in contact with the ground
Providing loaded stability for high-center-of-gravity vocational bodies
Reducing road shock transferred into the frame, body, equipment, and cab

Common Specifications

HAULMAAX EX 400

Suspension rating: 40,000 pounds
Installed suspension weight: Approximately 836 pounds
Approved gross vehicle weight: Up to approximately 83,000 pounds
Approved gross combination weight: Up to approximately 200,000 pounds
Job-site travel rating: Up to 60,000 pounds
Loaded ride-height range: Approximately 8 to 13.25 inches
Available axle spacings: Approximately 52, 54, and 60 inches

HAULMAAX EX 460

Suspension rating: 46,000 pounds
Installed suspension weight: Approximately 845 pounds
Approved gross vehicle weight: Up to approximately 88,000 pounds
Approved gross combination weight: Up to approximately 200,000 pounds
Job-site travel rating: Up to 70,000 pounds
Loaded ride-height range: Approximately 8 to 18.5 inches
Available axle spacings: Approximately 52, 54, 60, and 72.5 inches

HAULMAAX EX 520

Suspension rating: 52,000 pounds
Installed suspension weight: Approximately 939 pounds
Approved gross vehicle weight: Up to approximately 93,000 pounds
Approved gross combination weight: Up to approximately 250,000 pounds
Job-site travel rating: Up to 75,000 pounds
Loaded ride-height range: Approximately 8 to 13.25 inches
Available axle spacings: Approximately 52, 54, and 60 inches

All three versions provide up to approximately 17 inches of diagonal articulation. Actual vehicle capability may be limited by axle stops, frame design, tires, body equipment, driveline angles, or other manufacturer specifications.

Capacity, Ride Height, and Axle Travel

The HAULMAAX EX suspension rating must be matched to the selected drive axles, tires, wheels, brakes, frame, and vehicle gross-weight ratings. Installing a higher-rated suspension does not increase the legal or structural capacity of the complete vehicle.

Loaded ride height is measured from the drive-axle centerline to the bottom of the truck frame. The correct ride height depends on the suspension model, axle spacing, frame configuration, driveline geometry, tire size, and truck manufacturer’s installation specifications.

HAULMAAX EX provides up to 17 inches of diagonal articulation. This allows one side of an axle to move relative to the opposite side and helps maintain traction on uneven job sites.

Vehicle-installed axle stops or body and equipment clearances may restrict the available articulation

Ride Quality and Load Distribution

HAULMAAX EX uses a progressive spring arrangement to balance two different operating conditions.

When the truck is lightly loaded, the rubber spring system provides a more compliant response than many traditional severe-duty mechanical suspensions.

As payload weight increases, the progressive load springs become more involved and increase suspension stiffness. This helps control roll, body movement, and load shifting during cornering, braking, and job-site operation.

The equalizing beams distribute weight between the two drive axles as the truck moves across uneven terrain. This helps maintain tire contact and reduces extreme loading differences between the tandem axles.

Ride quality can also be influenced by tire pressure, cab suspension, wheelbase, body construction, frame stiffness, road conditions, payload placement, and whether shock absorbers are installed.

Suspension Controls and Adjustment Options

HAULMAAX EX is a passive mechanical rubber suspension. It does not use a height-control valve, electronic suspension controller, or driver-operated air-dump control.

Available adjustment and configuration provisions may include:

Bar-pin alignment shims
Transverse torque-rod shims
Progressive load spring weight-bias shims
Different loaded ride heights
Different axle spacings
Optional shock absorbers
Optional or required dual rebound straps
Application-specific torque-rod arrangements
Available beam lengths

Any alignment, weight-bias, or component adjustment should follow Hendrickson and vehicle-manufacturer procedures.

Alignment and Suspension Geometry

Correct axle alignment is essential for predictable handling, tire life, driveline operation, and suspension durability.

The original position of the frame hangers and axle brackets establishes the basic alignment of the drive axles. Bar-pin shims at the equalizing-beam end connections are used to make drive-axle alignment corrections.

Transverse torque-rod shims may be used to correct lateral axle alignment. Longitudinal torque-rod positioning and shimming can affect axle pinion angle.

Important alignment considerations include:

Drive-axle thrust angle
Axle-to-axle alignment
Lateral axle position
Pinion angle
Bar-pin shim position
Transverse torque-rod position
Frame-hanger location
Axle-bracket location
Ride height
Tire and suspension clearance

Alignment should be checked after axle or suspension repairs, bushing replacement, collision damage, abnormal tire wear, or complaints about vehicle tracking.

Axle, Brake, and Wheel-End Options

HAULMAAX EX is a suspension system and does not include a single universal axle, brake, or wheel-end package. The truck manufacturer specifies compatible components based on vehicle capacity and application.

The suspension may be paired with approved tandem drive axles using:

Drum brakes
Air disc brakes
Conventional wheel ends
Preset or unitized wheel ends
Dual rear wheels
Application-specific axle housings and ratios
Driver-controlled differential locks
Inter-axle differential locks
Traction-control systems

The selected axles must have ratings appropriate for the suspension capacity and vehicle application. Brake, wheel-end, tire, frame, and driveline clearances must be confirmed for the chosen ride height and axle spacing.

Common Applications

Dump trucks
Concrete mixer trucks
Refuse trucks
Logging trucks
Crane and boom trucks
Platform trucks
Fire and rescue vehicles
Heavy vocational tractors
Construction vehicles
Utility and infrastructure equipment
Job-site support vehicles
Specialized severe-duty vehicles

Additional applications require approval from Hendrickson and the vehicle manufacturer.

Vehicle, Axle, and Frame Compatibility

HAULMAAX EX is intended for approved heavy vocational chassis equipped with tandem rear-drive axles.

Compatibility depends on:

Truck manufacturer and chassis model
Vehicle gross and combination weight ratings
Drive-axle ratings
Frame width and rail dimensions
Axle spacing
Loaded suspension ride height
Driveshaft and pinion angles
Tire and wheel dimensions
Brake configuration
Body and auxiliary-equipment clearance
Lift-axle placement and loading
Outrigger installation
Required torque-rod configuration

Truck manufacturers may offer HAULMAAX EX as a factory suspension option on selected vocational chassis. Availability varies by model, axle rating, wheelbase, body installation, and production year.

Advantages

Heavy-duty construction for demanding vocational service
Available in suspension ratings up to 52,000 pounds
Up to 17 inches of diagonal articulation
Progressive spring response balances unloaded ride and loaded stability
Equalizing beams distribute weight between tandem axles
Rubber springs do not require an air supply to support the truck
No suspension air bags or height-control valves
Eliminates traditional fixed center bushings
Lower suspension weight than many conventional severe-duty designs
Strong roll stability for dump, mixer, refuse, and similar applications
Bar-pin connections permit drive-axle alignment
Approved for properly configured lift-axle vehicles
Several ride-height and axle-spacing configurations
Optional shock absorbers for improved damping

Limitations or Considerations

Does not provide the same ride characteristics as a full air suspension
Rubber bolster and progressive load springs require regular inspection
Bar-pin bushings and axle connections are critical wear points
Correct alignment depends on proper shim installation
Vehicle articulation may be limited by axle stops or equipment clearance
Suspension rating does not override axle, tire, wheel, brake, or legal weight limits
Shock absorbers are required for tractor and logging applications
Outrigger-equipped vehicles require dual rebound straps
Available ride heights and axle spacings vary by suspension rating
Liftable auxiliary axles can overload the suspension if operated incorrectly
Repairs may require special tools and heavy-component handling equipment
Generation-specific components may not always be interchangeable

Driver and Operator Experience

Drivers can expect HAULMAAX EX to feel firmer than many rear air suspensions, particularly when the vehicle is empty. The progressive rubber spring design is intended to reduce the harshness associated with some traditional mechanical suspensions while maintaining stability under load.

On uneven job sites, the equalizing beams and available articulation help the tandem axles follow changing terrain. This can improve tire contact and reduce wheel lift when crossing ruts, ramps, and uneven surfaces.

Operators should watch for:

Changes in vehicle lean
Increased rear-suspension noise
Harshness that was not previously present
Steering pull or dog-tracking
Uneven drive-tire wear
Excessive axle movement
Damaged rebound straps
Visible rubber-spring deterioration
Leaking shock absorbers
Changes in driveline vibration

These symptoms may indicate wear, misalignment, damaged components, improper loading, or another chassis problem.

Maintenance and Ownership Notes

HAULMAAX EX eliminates several maintenance points associated with air suspensions and traditional center-bushed walking-beam systems, but it still requires regular inspection.

Maintenance areas include:

Equalizing-beam end connections
Bar-pin bushings
Bar-pin alignment shims
Axle brackets
Longitudinal torque rods
Transverse torque rods
Rubber bolster springs
Progressive load springs
Rebound straps
Shock absorbers when equipped
Frame saddles and brackets
Mounting fasteners
Axle alignment
Tire-clearance areas

Technicians should inspect the progressive load springs every three months for tearing and deterioration. Hendrickson specifies replacement when a tear exceeds the published service limit.

A light film on a shock-absorber body may be normal misting. Visible fluid running from the seal can indicate an actual leak.

Critical fasteners should be inspected and tightened according to the applicable Hendrickson and truck-manufacturer specifications. Used fasteners identified as non-reusable in the service procedure should be discarded and replaced.

Common Suspension Problems

Worn bar-pin end bushings
Loose or incorrectly installed bar-pin shims
Drive-axle misalignment
Lateral axle misalignment
Damaged or deteriorated rubber bolster springs
Torn or compressed progressive load springs
Broken or damaged rebound straps
Leaking or worn shock absorbers
Loose suspension fasteners
Worn torque-rod bushings
Bent or damaged torque rods
Damaged axle brackets
Cracked or damaged frame brackets
Incorrect pinion angle
Uneven vehicle lean
Abnormal drive-tire wear
Excessive suspension noise
Driveline vibration
Reduced ride quality
Insufficient tire or component clearance

Identification Information

HAULMAAX EX can be identified by its tandem equalizing beams, angled rubber bolster springs, progressive load springs, frame saddles, bar-pin axle connections, and absence of conventional rear air bags or steel spring packs.

Before ordering parts, record:

Truck manufacturer
Truck model and production year
Vehicle identification number
Suspension model
Suspension capacity
Axle spacing
Loaded ride height
Drive-axle manufacturer and model
Frame width
Beam and saddle configuration
Bolster-spring design
Progressive load-spring part number
Torque-rod configuration
Rebound-strap configuration
Shock-absorber installation
Axle-bracket and bar-pin configuration

HAULMAAX EX Generation 1 and Generation 2 systems use updated component designs. Some components are not interchangeable, making accurate generation identification important before ordering replacement parts.

Buying Considerations

Required suspension capacity
Vehicle gross and combination weight ratings
Primary vocational application
Expected on-road and job-site operation
Payload requirements
Desired empty-ride quality
Loaded roll stability
Required articulation
Axle spacing
Loaded ride height
Frame dimensions
Drive-axle compatibility
Brake and wheel-end clearance
Lift-axle configuration
Outrigger installation
Shock-absorber requirements
Suspension generation
Replacement-parts availability
Dealer and technical support
Warranty coverage
Total installed and lifecycle cost

A complete chassis specification should be reviewed with the truck manufacturer, Hendrickson, the body builder, and the axle supplier before the suspension is ordered.

Variants and Configurations

HAULMAAX EX 400

The HAULMAAX EX 400 has a 40,000-pound suspension rating and is intended for vocational tandem applications that do not require the higher ratings of the 460 or 520 models.

HAULMAAX EX 460

The HAULMAAX EX 460 has a 46,000-pound suspension rating and offers the broadest published ride-height and axle-spacing ranges within the family.

HAULMAAX EX 520

The HAULMAAX EX 520 has a 52,000-pound suspension rating. It includes dual rebound straps and additional components appropriate for the higher-capacity configuration.

Generation 1

Earlier HAULMAAX EX systems use the original bolster-spring and saddle configuration. Replacement parts should be confirmed using the suspension identification and production information.

Generation 2

Updated HAULMAAX EX systems use revised bolster-spring and saddle components. Some Generation 1 and Generation 2 components are not interchangeable.

Shock-Equipped Configuration

Shock absorbers are required for tractor and logging applications and may be specified for additional ride control in other approved applications.

Dual-Rebound-Strap Configuration

Dual rebound straps are standard on the 52,000-pound model, required with outriggers, and available for certain 40,000- and 46,000-pound configurations.

Comparison to Similar Equipment

HAULMAAX EX vs Hendrickson PRIMAAX EX

HAULMAAX EX is a rubber mechanical suspension that does not require air springs to carry the vehicle. Hendrickson PRIMAAX EX is a severe-duty vocational air suspension designed to provide air-ride characteristics and controlled ride height.

HAULMAAX EX may be preferred for applications prioritizing loaded stability, articulation, simplicity, and resistance to air-system damage. PRIMAAX EX may be preferred when ride quality and air-suspension operation are greater priorities.

HAULMAAX EX vs Hendrickson HN

HAULMAAX EX uses equalizing beams with rubber bolster and progressive load springs. Hendrickson HN Vocational Suspension uses a different VariRate spring configuration intended for demanding vocational service.

HAULMAAX EX vs Hendrickson RT/RTE

HAULMAAX EX uses rubber springs and a lightweight equalizing-beam design. Hendrickson RT/RTE Mechanical Suspension is a traditional steel-spring walking-beam suspension known for rugged severe-duty service.

HAULMAAX EX vs Rear Air Suspension

HAULMAAX EX avoids air springs, height-control valves, and suspension air plumbing. A rear air suspension may provide a softer and more consistent ride but introduces additional pneumatic components and potential air-leak points.

Best Fit For

Dump trucks operating on roads and job sites
Concrete mixers requiring strong loaded stability
Refuse trucks with frequent loading and unloading cycles
Logging trucks requiring articulation and traction
Crane and boom trucks with approved suspension configurations
Platform and heavy vocational trucks
Fire and rescue apparatus
Fleets seeking a rubber suspension without air springs
Operations prioritizing payload and suspension weight
Applications requiring up to a 52,000-pound tandem suspension rating
Vehicles using approved pusher or tag axles
Operators needing several ride-height and axle-spacing choices

Related Vehicle and Trailer Types

Dump Trucks
Concrete Mixer Trucks
Refuse Trucks
Logging Trucks
Heavy vocational tractors
Crane and boom trucks
Platform trucks
Fire and rescue vehicles
Construction trucks

Related Truck and Trailer Models

Related Suspension Types

Vocational & Severe-Duty Suspensions
Mechanical & Leaf Spring Suspensions
Hendrickson PRIMAAX EX
Hendrickson PRIMAAX
Hendrickson HN Vocational Suspension
Hendrickson RT/RTE Mechanical Suspension
Hendrickson RS Series Suspension

Related Equipment Systems

Related Guides

Regulatory and Compliance Notes

The suspension’s published capacity does not determine the vehicle’s legal operating weight by itself. The truck must remain within all applicable gross vehicle, gross combination, axle, tire, wheel, brake, bridge-formula, and road-use limits.

Liftable pusher or tag axles can change the weight carried by the tandem suspension. Operators must not raise or unload an auxiliary axle when doing so would overload the HAULMAAX EX suspension, drive axles, tires, wheels, or frame.

Hendrickson’s published job-site travel ratings apply only under specified limited conditions. Job-site ratings are limited to no more than five percent of vehicle operation and speeds not exceeding five miles per hour. The appropriate axle ratings must also support the load.

Application approval should be confirmed with Hendrickson and the truck manufacturer, particularly when the vehicle includes outriggers, lift axles, specialized bodies, unusually high gross weights, or modified chassis components.

Real World Operating Notes

HAULMAAX EX is especially useful on vocational trucks that spend part of their operating time on uneven surfaces but still travel substantial distances on public roads.

The suspension’s articulation helps the drive axles follow uneven ground, but tire contact can still be affected by vehicle loading, axle stops, tire inflation, body stiffness, frame twist, and surface conditions.

A suspension problem may first appear as unusual tire wear, vehicle lean, changed handling, driveline vibration, or increased noise. These symptoms should not automatically be blamed on the rubber springs because axle alignment, torque rods, tires, wheel ends, frame components, or body installation may also be responsible.

When an auxiliary axle is lifted, more vehicle weight can transfer to the tandem drive suspension. Drivers and fleets must understand how auxiliary-axle operation changes individual axle and suspension loads.

Frequently Asked Questions

Is the Hendrickson HAULMAAX EX an air suspension?

No. HAULMAAX EX is a heavy-duty rubber mechanical suspension. It uses rubber bolster springs and progressive load springs rather than air springs to carry the vehicle.

What capacities are available?

HAULMAAX EX is available with published suspension ratings of 40,000, 46,000, and 52,000 pounds.

How much articulation does HAULMAAX EX provide?

Hendrickson publishes up to approximately 17 inches of diagonal articulation. Actual movement may be limited by the truck’s axle stops, frame, body, tires, or other components.

What trucks commonly use HAULMAAX EX?

It is commonly specified for dump trucks, concrete mixers, refuse trucks, logging trucks, cranes, platform trucks, and fire or rescue vehicles.

Does HAULMAAX EX require shock absorbers?

Shock absorbers are required for tractor and logging applications. They may be optional for other approved applications where additional damping or ride control is desired.

Can HAULMAAX EX be used with lift axles?

Yes, approved configurations can use liftable auxiliary axles. However, raising or unloading an auxiliary axle must not overload the rear suspension or other vehicle components.

Does the suspension require lubrication?

The rubber spring system and eliminated center bushings reduce lubrication requirements. Other chassis, axle, driveline, brake, and wheel-end components may still require lubrication according to their manufacturers’ schedules.

How is HAULMAAX EX aligned?

Drive-axle alignment is adjusted using shims at the bar-pin end connections. Transverse torque-rod shims may be used to adjust lateral axle position.

How is ride height measured?

Loaded ride height is measured from the centerline of the drive axle to the bottom of the truck frame.

Are all HAULMAAX EX parts interchangeable?

No. Generation 1 and Generation 2 systems include updated components, and certain parts are not interchangeable. The suspension generation should be confirmed before ordering parts.

What is the difference between HAULMAAX and HAULMAAX EX?

HAULMAAX EX is the updated family with revised suspension geometry, capacity options, materials, spring components, and application capabilities. Parts should be ordered using the exact suspension model and generation.

Availability and Where to Find

HAULMAAX EX is available as a factory-installed suspension option on selected heavy vocational truck chassis. Exact availability depends on the truck manufacturer, model, axle ratings, wheelbase, frame configuration, body installation, and application.

Replacement parts and service components are available through Hendrickson-authorized dealers, commercial truck dealers, suspension specialists, heavy-duty parts suppliers, and qualified truck repair facilities.

Before ordering a replacement component, provide the supplier with the truck identification, suspension rating, axle spacing, ride height, suspension generation, and original component numbers.

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