Hendrickson HN Vocational Suspension

Quick Facts

  • Manufacturer: Hendrickson
  • Product Type: Heavy-duty rear mechanical suspension
  • Suspension Family: HN Series
  • Spring System: Hendrickson VariRate rubber spring system
  • Axle Arrangement: Tandem rear axles
  • Primary Models: HN 40K, HN 46K, and HN 52K
  • Rated Capacities: 40,000, 46,000, and 52,000 pounds
  • Primary Applications: Dump trucks, mixers, refuse trucks, heavy vocational vehicles, and specialty equipment
  • Operating Environment: On-highway and off-highway vocational service
  • Maximum Diagonal Articulation: Approximately 17 inches in listed configurations
  • Lift-Axle Compatibility: Well suited to approved vehicles using multiple auxiliary lift axles
  • Page Slug: hendrickson-hn-vocational-suspension

Overview

The Hendrickson HN is a heavy-duty tandem rear suspension designed for demanding vocational trucks. It uses Hendrickson’s VariRate rubber spring system to balance loaded stability, articulation, ride quality, and relatively low suspension weight.

Unlike an air suspension, the HN does not depend on air springs, height-control valves, or suspension air lines. Rubber bolster springs support the chassis above the equalizing beams, while auxiliary springs engage as loading increases to provide additional stability.

The system is available in 40,000-, 46,000-, and 52,000-pound configurations. It is commonly associated with dump trucks, concrete mixers, refuse vehicles, and other vocational trucks operating across paved roads, construction sites, landfills, and uneven terrain.

Key Characteristics

  • Heavy-duty tandem rear mechanical suspension
  • Hendrickson VariRate rubber spring technology
  • Available in 40,000-, 46,000-, and 52,000-pound capacities
  • Designed for both on-highway and off-highway operation
  • Rubber bolster springs provide load support and articulation
  • Auxiliary springs engage under increasing load
  • Equalizing beams distribute weight between the tandem axles
  • No suspension air springs or height-control valves
  • Bar-pin beam-end connections support axle alignment and serviceability
  • Integrated shock absorbers help control axle hop
  • Approximately 17 inches of diagonal articulation in listed configurations
  • Compatible with approved auxiliary lift-axle arrangements

Major Components

  • Equalizing beams
  • Rubber bolster springs
  • Auxiliary load springs
  • Suspension saddle assemblies
  • Frame brackets
  • Axle brackets
  • Bar-pin beam-end bushings
  • Longitudinal torque rods
  • Transverse torque rods where required
  • Shock absorbers
  • Rebound straps
  • V-shaped bolster-spring brackets
  • Auxiliary-spring brackets
  • Alignment shims
  • Mounting bolts, washers, and locknuts
  • Drive axles, brakes, and wheel ends supplied as part of the complete chassis configuration

How the Suspension System Works

The HN uses equalizing beams to connect and control the two rear axles. The beams pivot as the axles move over uneven terrain, helping distribute weight between the forward and rear drive axles.

Diagonally positioned rubber bolster springs support the chassis above the beams. These rubber elements compress and change shape as the vehicle is loaded or the axles articulate. Their variable spring characteristics allow the system to respond differently when the truck is empty, partially loaded, or carrying a full payload.

Auxiliary springs engage as loading increases. This provides additional resistance and roll stability when the truck is heavily loaded, dumping, cornering, or maneuvering on uneven ground.

Shock absorbers control rapid axle and suspension movement. Torque rods control braking, acceleration, lateral, and rotational forces while keeping the axles correctly positioned beneath the frame.

Suspension Position and Function

The HN is installed beneath the rear of a heavy vocational truck. It connects the tandem rear axles to the chassis and supports the rear portion of the vehicle, body, equipment, and payload.

The suspension performs several functions:

  • Supports the rear chassis and payload
  • Distributes weight across both tandem axles
  • Allows the axles to articulate over uneven terrain
  • Helps maintain tire contact and traction
  • Controls axle movement during braking and acceleration
  • Provides roll stability during cornering and dumping
  • Absorbs road shock through the rubber spring system
  • Helps reduce axle hop through integrated shock absorbers
  • Maintains axle position and alignment beneath the frame

Common Specifications

  • HN 40K Capacity: 40,000 pounds
  • HN 40K Installed Weight: Approximately 935 pounds
  • HN 40K Site-Travel Rating: 55,000 pounds
  • HN 40K Approved GVW: Up to 73,000 pounds
  • HN 40K Approved GCW: Up to 160,000 pounds
  • HN 46K Capacity: 46,000 pounds
  • HN 46K Installed Weight: Approximately 948 pounds
  • HN 46K Site-Travel Rating: 60,000 pounds
  • HN 46K Approved GVW: Up to 80,000 pounds
  • HN 46K Approved GCW: Up to 190,000 pounds
  • HN 52K Capacity: 52,000 pounds
  • HN 52K Installed Weight: Approximately 955 pounds
  • HN 52K Site-Travel Rating: 65,000 pounds
  • HN 52K Approved GVW: Up to 80,000 pounds
  • HN 52K Approved GCW: Up to 245,000 pounds
  • Reference Axle Spacing for Published Weight: 54 inches
  • Diagonal Articulation: Approximately 17 inches in listed configurations

Published installed weights include the suspension, torque rods, axle brackets, shock absorbers, and frame brackets for a 54-inch axle-spacing configuration. Actual vehicle specifications may differ.

Capacity, Ride Height, and Axle Travel

HN capacity is determined by the selected suspension model and the ratings of the complete vehicle. The HN 40K supports common 40,000-pound tandem applications, while HN 46K and HN 52K models provide higher nominal ratings for heavier vocational configurations.

The rubber springs compress as payload increases, so chassis height changes with loading. The system does not automatically maintain a constant ride height like an air suspension.

Approximately 17 inches of diagonal articulation is available in listed configurations. This allows one axle end to rise while the opposite axle end moves downward, helping the tires remain in contact with uneven ground.

Suspension capacity and site-travel ratings do not override the ratings of the axles, tires, wheels, brakes, frame, or complete vehicle.

Ride Quality and Load Distribution

The VariRate spring system changes its effective spring response according to loading. The rubber bolster springs help provide compliance when the truck is lightly loaded, while the auxiliary springs add support and stability as weight increases.

Equalizing beams distribute weight between the forward and rear axles. This can help maintain traction when one axle encounters a bump, rut, or depression.

The HN generally provides a firmer ride than a vocational air suspension, particularly when the truck is empty. Its priorities are stability, articulation, durability, and predictable load support under demanding operating conditions.

Suspension Controls and Adjustment Options

The HN does not require driver-operated suspension controls, height-control valves, or suspension air pressure. Load support and spring response are controlled mechanically by the rubber bolster springs, auxiliary springs, equalizing beams, and shock absorbers.

Service-related adjustments can include:

  • Rear axle alignment through the bar-pin beam-end connections and approved alignment shims
  • Auxiliary spring shimming in applicable configurations
  • Transverse torque-rod adjustment where an adjustable rod is installed
  • Driveline-angle correction through approved chassis procedures
  • Brake and wheel-end adjustments according to axle-manufacturer requirements
  • Suspension components should only be adjusted using Hendrickson and vehicle-manufacturer procedures.

Alignment and Suspension Geometry

Correct tandem alignment helps the truck track properly and limits tire scrub. The bar-pin beam-end design permits axle alignment through approved shimming procedures.

Alignment should be checked when the vehicle exhibits irregular tire wear, dog tracking, steering correction, reduced fuel efficiency, or evidence that an axle has moved.

Important inspection points include:

  • Bar-pin beam-end bushings
  • Axle brackets
  • Alignment shims
  • Equalizing beams
  • Longitudinal and transverse torque rods
  • Frame brackets
  • Suspension saddles
  • Axle spacing
  • Thrust angle
  • Driveline angles

Rear axle alignment can also affect front tire wear and overall vehicle handling.

Axle, Brake, and Wheel-End Options

HN suspensions are used with compatible heavy-duty tandem drive axles. Drive-axle manufacturer, axle model, gear ratio, differential configuration, brake type, and wheel-end package are selected as part of the complete vehicle specification.

Depending on the chassis, HN installations may use drum brakes or air disc brakes. Hub, bearing, seal, tire, and wheel options vary by axle and vehicle manufacturer.

The usable vehicle capacity is limited by the lowest-rated component. A 52,000-pound HN suspension does not create a 52,000-pound legal axle-group rating when the axles, tires, wheels, brakes, frame, or regulations establish a lower limit.

Common Applications

  • Dump trucks
  • Concrete mixer trucks
  • Refuse trucks
  • Roll-off and hook-lift trucks
  • Construction vehicles
  • Mining-support trucks
  • Municipal service vehicles
  • Heavy equipment service trucks
  • Oilfield vehicles
  • Water trucks
  • Snowplows and severe-weather vehicles
  • Vocational trucks using multiple lift axles
  • Fire and rescue vehicles with an application-specific HN FR configuration

Vehicle, Axle, and Frame Compatibility

HN compatibility depends on the vehicle manufacturer, frame dimensions, axle spacing, drive-axle models, axle brackets, driveline geometry, brake system, tire size, gross vehicle weight rating, and intended operation.

The suspension is designed for tandem rear axles. Common published specifications use a 54-inch axle-spacing configuration, but other application-specific arrangements may exist.

HN can be useful on vehicles equipped with liftable pusher or tag axles because its relatively low installed weight helps preserve payload capacity. The entire auxiliary-axle installation must still be approved by the vehicle and suspension manufacturers.

An HN suspension should not be installed or substituted based only on its nominal capacity. Frame strength, crossmember placement, axle ratings, brake capacity, and driveline geometry must be evaluated.

Advantages

  • 40,000-, 46,000-, and 52,000-pound capacity options
  • Designed for demanding vocational operation
  • Good loaded stability
  • Approximately 17 inches of diagonal articulation
  • Rubber springs absorb road shock without suspension air lines
  • No height-control valve or air-suspension plumbing
  • Equalizing beams help distribute weight between the tandem axles
  • Auxiliary springs provide additional loaded support
  • Bar-pin connections simplify axle-alignment correction
  • Integrated shock absorbers help control axle hop
  • Suitable for approved vehicles using multiple lift axles
  • Relatively low installed weight for its capacity and application
  • Reduced metal-to-metal contact within the spring system

Limitations or Considerations

  • Firmer empty ride than many rear air suspensions
  • Ride height changes as vehicle load changes
  • Rubber bolster and auxiliary springs age and require inspection
  • Does not provide automatic chassis leveling
  • Suspension tuning depends on correct rubber spring and auxiliary spring selection
  • Improper auxiliary-spring shimming can affect ride and stability
  • Bar-pin bushings and axle brackets can wear or loosen
  • Suspension capacity does not determine the vehicle’s legal payload
  • Site-travel ratings apply only under restricted operating conditions
  • Replacement parts vary by model and production date
  • Not every configuration is appropriate for every lift-axle arrangement
  • Mechanical damage or unauthorized welding can make structural components unsafe

Driver and Operator Experience

Drivers can expect a stable and predictable suspension when the truck is heavily loaded. This is especially valuable when carrying a high-center-of-gravity body, cornering, working on uneven terrain, or operating a dump body.

The unloaded ride is generally firmer than that of an air suspension. Rubber bolster springs and shock absorbers help control harshness, but the HN remains a heavy vocational mechanical suspension.

Operators should report excessive bouncing, axle hop, leaning, clunking, poor tracking, or sudden changes in chassis height. These symptoms may indicate damaged rubber springs, worn bushings, loose brackets, failed shocks, or improper axle alignment.

Maintenance and Ownership Notes

  • Inspect rubber bolster springs for cuts, cracks, separation, bulging, or excessive deformation.
  • Check auxiliary springs for wear, damage, proper clearance, and correct shimming.
  • Inspect rebound straps for tearing, fraying, or separation.
  • Examine equalizing beams for cracks, damage, or unauthorized repairs.
  • Inspect bar-pin beam-end bushings for looseness or movement.
  • Measure axle-bracket width when a beam-end connection shows movement.
  • Check saddle assemblies and frame brackets for cracks or loose fasteners.
  • Inspect longitudinal and transverse torque rods and their bushings.
  • Check shock absorbers for leakage, damage, and worn mounting bushings.
  • Inspect axle alignment and tire-wear patterns.
  • Follow Hendrickson torque specifications for all structural fasteners.
  • Replace matched rubber bolster springs or related components as directed by the applicable service procedure.
  • Never weld, torch, or attach material to the equalizing beams.

Common Suspension Problems

  • Cracked or deteriorated rubber bolster springs
  • Damaged or compressed auxiliary springs
  • Incorrect auxiliary-spring clearance
  • Torn or frayed rebound straps
  • Worn bar-pin beam-end bushings
  • Movement between the equalizing beam and axle bracket
  • Bent, spread, or damaged axle brackets
  • Loose saddle or frame-bracket fasteners
  • Worn torque-rod bushings
  • Damaged longitudinal or transverse torque rods
  • Leaking or ineffective shock absorbers
  • Axle hop during acceleration or braking
  • Irregular drive-tire wear
  • Tandem axle misalignment
  • Vehicle dog tracking
  • Uneven chassis height
  • Excessive empty-ride harshness
  • Suspension noise caused by loose or worn components
  • Cracked or damaged equalizing beams

Identification Information

Begin with the vehicle identification number, manufacturer build sheet, suspension model, axle spacing, and vehicle production date. HN components have changed across different generations and production periods.

Important identification information includes:

  • Vehicle identification number
  • Truck manufacturer and model
  • Model year and production date
  • HN 40K, HN 46K, or HN 52K designation
  • Earlier HN 402, HN 462, or HN 522 designation
  • Axle spacing
  • Saddle height
  • Drive-axle model
  • Axle-bracket configuration
  • Bolster-spring part number
  • Auxiliary-spring part number
  • Equalizing-beam part number
  • Torque-rod configuration
  • Existing component numbers

Earlier HN 400 and HN 460 systems and later HN 402, HN 462, and HN 522 systems may use different components. Production date must be considered when ordering replacement parts.

Buying Considerations

  • Confirm whether the vehicle has HN 40K, HN 46K, or HN 52K.
  • Identify the production generation and exact model designation.
  • Verify axle spacing and saddle height.
  • Compare suspension capacity with axle, tire, wheel, brake, and frame ratings.
  • Determine the expected percentage of on-highway and off-highway operation.
  • Review the vehicle’s lift-axle configuration.
  • Inspect all rubber bolster and auxiliary springs.
  • Check the rebound straps.
  • Inspect equalizing beams for damage or unauthorized welding.
  • Check bar-pin bushings and axle brackets for movement.
  • Inspect torque rods, shocks, saddles, and frame brackets.
  • Examine drive tires for evidence of axle misalignment.
  • Road-test the vehicle for axle hop, clunking, harshness, and poor tracking.
  • Confirm parts availability using the VIN, production date, and component numbers.

Variants and Configurations

  • HN 40K: Tandem mechanical suspension with a nominal 40,000-pound rating.
  • HN 46K: Tandem mechanical suspension with a nominal 46,000-pound rating.
  • HN 52K: Tandem mechanical suspension with a nominal 52,000-pound rating.
  • HN 402: Earlier numerical designation associated with the 40,000-pound HN configuration.
  • HN 462: Earlier numerical designation associated with the 46,000-pound HN configuration.
  • HN 522: Earlier numerical designation associated with the 52,000-pound HN configuration.
  • HN FR Series: Specialized fire-and-rescue suspension family with application-specific ratings and components.
  • Lift-Axle Vehicle Configuration: Approved HN installations used with pusher or tag axles on multi-axle vocational trucks.
  • Application-Specific Spring Configuration: Different bolster springs, auxiliary springs, shims, saddle heights, and torque rods selected for the vehicle’s weight and stability requirements.

Comparison to Similar Equipment

Compared with the Hendrickson HAULMAAX EX, the HN uses an earlier VariRate rubber spring and equalizing-beam architecture. HAULMAAX EX represents a newer heavy-duty rubber-suspension design with updated weight, articulation, and maintenance features.

Compared with the Hendrickson PRIMAAX EX, the HN is a mechanical rubber suspension rather than an air suspension. HN avoids suspension air components and provides strong loaded stability, while PRIMAAX EX generally provides better empty and loaded ride isolation.

The Hendrickson HAS Air Suspension is better suited to fleets prioritizing highway ride quality with limited off-highway operation. HN is intended for more demanding vocational work where mechanical simplicity and stability are important.

Compared with the Hendrickson RT/RTE Mechanical Suspension, HN uses rubber bolster and auxiliary springs instead of conventional steel leaf-spring packs.

Best Fit For

  • Dump, mixer, and refuse fleets
  • Vocational trucks operating on paved roads and work sites
  • Vehicles requiring high loaded roll stability
  • Operations needing up to 52,000 pounds of suspension capacity
  • Trucks requiring substantial tandem articulation
  • Vehicles using approved auxiliary lift axles
  • Fleets preferring mechanical suspension over rear air suspension
  • Applications where durability and predictable load support matter more than premium unloaded ride quality

Related Vehicle and Trailer Types

  • Complete Guide to Semi Truck Types
  • Dump trucks
  • Concrete mixer trucks
  • Refuse trucks
  • Roll-off trucks
  • Heavy vocational trucks
  • Municipal service vehicles
  • Oilfield trucks
  • Construction-support vehicles
  • Fire and rescue vehicles
  • Heavy equipment service trucks

Related Truck and Trailer Models

Related Suspension Types

Related Equipment Systems

Related Guides

Regulatory and Compliance Notes

An HN-equipped vehicle must remain within all applicable gross vehicle, axle-group, bridge-formula, tire, wheel, brake, frame, and roadway limits. The suspension’s nominal capacity or site-travel rating does not authorize operation above legal weight limits.

Hendrickson’s site-travel ratings apply to restricted operation. They are limited to no more than 5 percent of vehicle operation at speeds not exceeding 5 mph. Liftable pusher or tag axles should only be raised or unloaded to improve off-road maneuverability or when the vehicle is unloaded.

Neither the suspension nor axle site-travel rating may be exceeded. The vehicle manufacturer determines the complete vehicle capacity.

Real World Operating Notes

The HN performs best on trucks that carry substantial payload and require stability on uneven sites. Its auxiliary springs become increasingly important as the truck is loaded, particularly during dumping, turning, or maneuvering with a high center of gravity.

Rubber spring condition can materially change the way the truck rides and sits. Springs that are deteriorated, incorrectly matched, or improperly shimmed can produce lean, harshness, instability, or unequal load distribution.

Tandem alignment should be checked whenever unusual tire wear develops. Replacing tires without correcting worn bar-pin bushings, shifted axle brackets, or incorrect alignment will not solve the underlying problem.

Frequently Asked Questions

Is the Hendrickson HN an air suspension?

No. HN is a mechanical tandem suspension using rubber bolster and auxiliary springs.

What is the VariRate spring system?

VariRate is Hendrickson’s rubber spring system designed to provide different ride and stability characteristics as vehicle loading changes.

What capacities are available?

Current listed HN models have nominal capacities of 40,000, 46,000, and 52,000 pounds.

What is the difference between HN 40K and HN 402?

HN 40K is the current capacity-based naming format. HN 402 is an earlier model designation associated with the 40,000-pound configuration.

How much articulation does the HN provide?

Listed HN configurations provide approximately 17 inches of diagonal articulation.

Does the HN require shock absorbers?

HN configurations use integrated shock absorbers to control suspension movement and help reduce axle hop.

Can HN be used with lift axles?

Yes. The suspension is suited to approved vehicles using auxiliary lift axles, but axle loading and site-travel restrictions must be followed.

Does HN maintain a constant ride height?

No. As a mechanical rubber suspension, its chassis height changes as the springs compress under load.

What commonly causes an HN-equipped truck to lean?

Possible causes include damaged or mismatched bolster springs, worn auxiliary springs, incorrect spring shimming, loose brackets, or uneven vehicle loading.

Are HN bolster springs replaced individually?

Replacement requirements depend on the component and service procedure. Rubber bolster springs are commonly serviced as matched components to preserve even suspension performance.

Can an HN equalizing beam be welded?

Hendrickson warns against welding, heating, torching, or attaching material to the equalizing beam. Damaged components should be evaluated and replaced according to the manufacturer’s procedures.

Is HN suitable for highway operation?

Yes. HN is designed for vocational vehicles operating both on highways and at off-highway work sites.

Availability and Where to Find

The Hendrickson HN can be found on existing dump trucks, mixers, refuse trucks, lift-axle vocational vehicles, fire apparatus, and other heavy-duty equipment. New vehicle availability depends on the truck manufacturer, model, capacity, and current factory options.

Replacement bolster springs, auxiliary springs, bushings, rebound straps, equalizing beams, torque rods, shocks, brackets, and mounting hardware are available through Hendrickson distributors, commercial truck dealers, suspension specialists, and heavy-duty parts suppliers.

Product information and specifications can be checked through Hendrickson’s official HN VariRate Spring Suspension page, HN technical procedure, and HN parts-list resource.

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