• Dead Band
— +/- 2°

HCV with Integral Dump
Hendrickson’s HCV with integral dump features a high-flow
design for rapid exhaust to save drivers time and effort as
they load, unload and get back on the road.
The dump valve automatically discharges the air springs
with the setting of the trailer parking brake and begins
to air up with release of the brake. Integrating the dump
function in the HCV eliminates components and simplifies
plumbing maintenance and installation.

Exhaust Function
• Automatic

— Dumps when trailer parking brake engages
• Dump flow rate

— 875 L/Min (31 cfm)
• Dump port

— Normally closed
• Dumps full suspension 40 percent faster
than HCV with add-on dump valve
— Integral = 12 seconds

— Add-on = 20 seconds
For additional information:
Controls Parts Catalog — L1182
Download current literature at
www.hendrickson-intl.com

UNDERSTANDING AIR SUSPENSIONS

17

UNDERSTANDING

Loading Dock
During docked loading and unloading with tow motors
or forklifts, three trailer reactions can occur: trailer deck
height change, trailer drop and trailer walk. Trailers
equipped with air suspensions in a trailing arm arrangement (figure1) can experience all three phenomena.
In addition, all trailers will exhibit a drop of between
1 to 1.5 inches due to tire deflection.

Trailing arm
Figure 1

Trailer deck height change refers to the variation in
deck height of an air suspension equipped vehicle
relative to the dock after dumping the air from the
system. In general, air suspension trailers equipped
with a dump valve
will lower 2.5 to
3.5 inches with air
exhausted. The trailer
comes to rest on
internal air spring
bumpers. Resting on
the bumpers, the trailer becomes extremely stable with
only significant motion resulting from tire deflection.

SOLUTIONS

Trailer drop, downward trailer travel that results from a
forklift entering during cargo transfer, occurs due to the
inherently low spring rate
that gives the suspension
its soft ride. Trailer drop
does not include trailer
deck height changes for air
suspensions. Trailer drop
does not occur if the air
springs have been dumped
and the trailer is resting
on the air spring bumpers.
Trailers with mechanical
spring suspensions may
drop about 1.75 inches.
Trailer walk refers to horizontal trailer movement away
from the dock caused by a forklift entering and exiting
the trailer for cargo transfer. This horizontal movement
can be caused by the suspension trailing arm’s downward
travel due to trailer drop. Even a mechanical suspension
can exhibit walk when a heavily loaded forklift repeatedly
enters the trailer with speed and stops abruptly near the
front. Similarly, a loaded trailer sitting for an extended
period of time can lose air pressure in its air springs,
allowing the trailer deck to gradually drop. Again, this
can result in forward movement that could shift the
trailer away from the dock.

THE HENDRICKSON ADVANTAGE
Hendrickson offers several solutions to the trailer
industry’s loading dock concerns. Because specific
applications and requirements vary from fleet to fleet,
we provide a variety of solutions to match virtually
every loading dock operation.

18

To maintain dock height, which naturally minimizes
drop and walk, specify SURELOK®. Featuring sturdy
mechanical support legs that automatically rotate and
lock in place over suspension trailing arms when
the trailer brakes engage, SURELOK minimizes trailer
drop and walk. When using SURELOK, trailer drop is

AIR SUSPENSIONS
generally unnoticed. Support legs automatically return
to their neutral position when the parking brakes are
released.
Used in conjunction with an automatic dump valve,
SURELOK® holds the deck height change to about an
inch while virtually eliminating drop and walk in almost
all loading conditions.

SURELOK holds the trailer
at dock height during
loading and unloading,
limiting the vertical and
horizontal movements
that result in trailer
drop and trailer walk.

When trailer walk is a concern, but deck height is not,
dump valves may be the answer.
Controlled by the driver, manual dump valves lower
the trailer between 2.5 and 3.5 inches at the door sill.
Trailers may descend slowly or experience a slight
one-time drop from discharge of residual air in the
bags as a forklift initially enters the trailer. During
cargo transfer, a manual valve limits trailer drop to
tire deflection and minimizes walk.

DST exhausts more than twice as fast as conventional
automatic dump valves,
and in most cases, brings
the trailer to rest on the
internal air spring bumpers
before the trailer parking
brakes fully engage. The
trailer deck height thus
falls between 2.5 and 3.5
inches, and DST limits
trailer drop to tire deflection and minimizes walk without
requiring additional driver intervention.
For the fleet owner, this means more efficient trailer
loading and unloading.
For additional information:
Loading Dock Approach Procedure — B109
Trailer Loading Dock Terms and Solutions — L816
SURELOK Flyer — L622
DST Dock Stabilizing Technology Flyer — L781
Download current literature at www.hendrickson-intl.com

DST Technology —
Another Valve Option
®

Available on VANTRAAX® systems, DST® Dock Stabilizing
Technology™ addresses loading dock issues of trailer drop
and walk. DST combines refined suspension geometry,
optimized plumbing and our patented HCDDV Height
Control Differential Dump Valve.

UNDERSTANDING AIR SUSPENSIONS

19

VALUE ADDED

UNDERSTANDING

Features and Options
Where do fleets and owner operators
find a competitive advantage today?
Through reduced maintenance, lighter
weight and increased durability.

For today’s and tomorrow’s haulers, Hendrickson fuses
quality and innovation into all of its products. Great
emphasis is placed on research and development to refine
our suspension systems and develop cost-effective
options that add enduring value to equipment.

THE HENDRICKSON ADVANTAGE
Hendrickson’s INTRAAX® and VANTRAAX® systems exhibit a
variety of features and options to help haulers keep one step
ahead of the competition. The industry’s first standard trailer
Cam Tube System™, ZMD® ZERO MAINTENANCE DAMPING®

Technology, an optional factory-applied Soft Coat Finish,
our LDA™ Large-Diameter Axle and the UBL™ UNDER
BEAM LIFT ™ all exemplify Hendrickson’s theory of
continuous innovation.

Cam Tube System™

passing the seals becomes effectively diluted, minimizing the
potential of damage or wear.

Throughout the
trucking industry,
S-cam journal
service life and ease
of maintenance
remain among
the most criticized
features of
conventional trailer
S-cam brake designs.
With the addition
of extended-service brake and hub systems, the need arose
to extend maintenance intervals and durability of the cam
supports to match.
Industry studies reveal that S-cam bushing life is a function
of contaminant levels in the areas where the cam
journals contact the bushings. The basic design principle
behind our Cam Tube System™ is to keep contaminants
away from the camshaft. The Cam Tube System includes
a modular steel cartridge that encloses the S-cam shaft
on each wheel-end assembly. We encase the camshaft
support bushings and seals at each end of this cartridge.
The spring-loaded seals greatly limit the potential of
contaminant entry by providing two redundant barriers
to entry. Ozone seal resistant material prevent degradation
by sustaining the life of the rubber. This system holds seven
times more grease than conventional designs. Any debris
20

When compared to traditional trailer brake designs that
have separate seals surrounding each journal and bushing individually, Hendrickson’s Cam Tube System reduces
contaminant entry points by 50 percent.
(See Cam Tube System flyer — L1214 for additional
information.)

ZMD ZERO MAINTENANCE DAMPING
®

®

ZMD® is available as a premium on select VANTRAAX®
and INTRAAX® integrated air suspension systems and as
a standard component on ULTRAA-K® integrated air slider
suspension systems. ZMD technology eliminates shock absorbers
all together and integrates the damping function traditionally
performed by the shock within the air spring itself. ZMD
air springs exchange pressurized air through channels that
interconnect the bellows and piston of this patent-pending
air spring.
Unlike a shock absorber whose damping capacity is finite
and deteriorates with age, ZMD air springs are designed to
provide continuous damping rates over the life of the air
spring. Robust chain down stops provide maximum durability
which helps reduce labor costs and maintenance over the
life of the trailer.
(See ZMD flyer — L1209 for additional information.)

AIR SUSPENSIONS
LDA™ Large-Diameter Axle
Since the first handcart, haulers sought lighter weight
equipment — more often than not by substituting lighter
materials and sacrificing strength for a weight reduction.
Hendrickson developed the LDA™, a 5-3/4-inch axle that
reduces trailer suspension weight while actually improving
component and system strength. By increasing the diameter
of the traditional 5-inch axle by about three-quarters of an
inch, it allows for the use of a thinner axle wall.
The standard axle diameter in Europe, the road proven
LDA tube allows the use of a slightly thinner wall for a
more efficient application of materials. In other words —
there is significant weight savings and increased bending
and torsional stiffness with comparable overall strength
to a 5-inch axle tube.
LDA generates a weight savings of between 20 and 27
pounds for each axle, depending on axle capacity.
In addition to matching the structural durability of the
5-inch tube, the larger diameter increases bending and
torsional stiffness by more than 14 percent. The reduced
tube deflection keeps the axle straighter under loads to
help improve fuel efficiency and enhance tire life. Greater
torsional rigidity also boosts roll stability.
As the largest trailer axle manufacturer in the North American
market, Hendrickson’s state-of-the-art production capabilities
such as friction-welded spindles and induction hardening allow
us to manufacture superior axles known for their unmatched
straightness and consistent construction.
LDA features the same neutral-toe alignment and long
lasting heat-treated components as our 5-inch axles and
are available with HN and HP spindles, as well as an
array of wheel-end options.

UBL™ UNDER BEAM LIFT™
Hendrickson’s UBL™ UNDER BEAM LIFT™ lets fleets
and owner-operators put the advantages of INTRAAX®
to work in liftable applications. Liftable axles offer
operational flexibility, extend tire life, improve trailer
maneuverability, allow vehicles to carry more payload
and can even save on road tolls. The UBL is a sturdy,
lightweight and easy-to-install lift mechanism. When
combined with INTRAAX, UBL provides the lightest
integrated lift system available today, increasing your
productivity and profitability.
(See UNDER BEAM LIFT flyer — L727 for additional
information.)

Soft Coat Finish / Hot Dip Wax
Harsh road and weather conditions take their toll on
equipment. With many fleets extending trade-in cycles for
equipment, haulers look for ways to extend the life of their
trailers. Hendrickson’s factory-applied Soft Coat Finish and
Hot Dip Wax are coatings that enhance resistance to corrosion
and rust, keeping suspensions on the road longer.
When stone chips occur on conventionally painted
suspensions, water can migrate under the paint leading
to rust and corrosion. Remaining soft and pliable,
Hendrickson’s Soft Coat Finish and Hot Dip Wax option
cushion impacts from road debris to yield a surface less
susceptible to chipping.
Before final assembly, Soft Coat Finish is robotically applied
and Hot Dip Wax is dipped on clean, non-primed surfaces
covering all hard-to-reach areas. This process replaces the
finished coat process. Soft coat paint and hot dip wax withstands accelerated corrosion tests, passing 2,000 hours in a
salt-spray environment. This exceeds the capacity of most
finishes used in the industry today.
Soft Coat is an available option on INTRAAX and VANTRAAX®
integrated air suspension systems. Hot Dip Wax is only available
on ULTRAA-K® integrated air slider suspension systems.

UNDERSTANDING AIR SUSPENSIONS

21

UNDERSTANDING

EXTENDED -SERVICE

Wheel-End

Options

As fleets and owner operators focus on reducing operating
costs, maintenance intervals and warranty costs, extended-service wheel-ends offer excellent potential to fulfill
goals pertaining to cost reductions.

Wheel-end Damage
Two main factors contribute to wheel-end damage:

High Operating Temperatures: The primary method to
reduce wheel-end operating temperature is lubrication.
Poor quality or lack of lubricant can damage wheel ends.
Contamination: Contaminants not only affect the integrity
of the lubricants but can be critical to the life of the wheel
seal as well. There are four primary conduits for contaminants
to enter the wheel-end:
• A damaged or worn seal can create a pathway for
contaminants to enter and for lubricants to exit the
wheel-end. Proper seal installation is vital to the life

and performance of the seal. When replacing a seal,
follow the seal manufacturer’s instructions to ensure
proper seal positioning.
• Improper bearing adjustment may result in excessive
end play or preload, either of which can shorten
bearing life. Excessive end play could also shorten
seal life.
• Water can enter the hubcap by way of the ventilation
ports, thus compromising the integrity of the lubricant.
Also, leakage around the mounting surface can occur
if hubcap bolts are not installed to the proper torque
specification.
• Contamination of the wheel-end interior prior to
initial installation can also compromise service life.
This type of contamination is commonly overlooked
during the installation process due to the misconception
that “because the hub is new, it is clean inside.”

THE HENDRICKSON ADVANTAGE
Hendrickson Trailer Commercial Vehicle Systems provides
fully integrated suspensions including extended-service
wheel-ends. Integrated, modular systems present an
opportunity to enhance end-user value in the area of
maintenance and operating expenses, as well as improve
productivity and operating efficiency. These fully integrated
systems also provide the customer with a single source
supplier. The following items are contributors to our
quality wheel-end products:

• Companion Parts — Hendrickson applies stringent
screening requirements and techniques to ensure
that only high quality, dependable wheel-end
components are offered.

22

• Quality Control — Clean and dry storage is provided
for all wheel-end components.
• Skilled Labor Force — Hendrickson’s skilled and
qualified personnel combined with our quality control
programs allow us to offer outstanding extended
wheel-end warranty coverage.
• Production Control Systems — Detailed wheel-end
installation procedures are controlled throughout the
assembly process. No detail is overlooked to provide
the finest quality assembly.

AIR SUSPENSIONS
RTR® READY-TO-ROLL® wheel-end packages offer
a variety of extended-service options and a wide
array of individual components that allow fleets
and owner operators to customize their running
gear to meet specific needs and requirements.
HXL7®
Wheel-end

HXL Hendrickson Extended-Life wheel-end
packages are designed for low maintenance and
long life and offer the convenience of a single
supplier for support and peace of mind from the
most trusted name in the trailer industry.
Properly installing wheel ends requires time,
manpower, and most importantly, attention to
detail. Our certified wheel-end technicians take
the time to ensure that HXL components like
spindle nuts, bearings, seals, hubs, lube, hub
caps, drums and dust shields are installed the
right way every time.
Hendrickson’s Extended-Life wheel-end packages
include our patented PRECISION spindle nut
system. This innovative 2-piece spindle nut system
provides fine-tuned adjustment increments to
achieve more precise end play settings than
traditional and more complicated 3-piece spindle
nut systems.

Spindles
Limited Warranty*
Hub Material

On-highway
Off-highway
Ductile Iron
ADI
Aluminum

Lube Type
Hub Cap

Features
TIS Capable**

Patented Ventilation System
PRECISION Spindle Nut
Allows for wide base tires with
2-inch offset rims

PRECISION240®
nut system
PRECISION nut systems have nearly five times the
adjustment resolution of other similar systems and
guarantee that bearings are set correctly the first
time. Hendrickson installs PRECISION nuts using
state-of-the-art equipment, allowing us to achieve
precise adjustment in light preload, which maximizes
seal and bearing life.

(See READY-TO-ROLL WHEEL ENDS flyer —
L1200 for additional information.)
HXL3®

HXL5®

HXL7®

HN / HP

HN / HP

HP Only

3-Year
1-Year
X
X
X
SAE 80/90 Gear Oil or
75-90 Synthetic

5-Year
3-Year
X
X
X

7-Year
3-Year
X
X
X

Semi-fluid Grease

Semi-fluid Grease

Ventless Bolt-on

Ventless Bolt-on

X
X

X
X

Ventless, Corrosionresistant Bolt-on
X