is indicated. If one steer tire shows feather wear and the other steer tire has normal wear, a combination of toe and drive axle or chassis misalignment is indicated.
Cupping — Localized, dished out areas of fast wear creating a scalloped appearance around the tire. Cupping, which appears around the tire on the shoulder ribs,
may also progress to adjoining ribs, see TMC RP 219A publication, page 7.
Cupping is usually a result of moderate-to-severe imbalance, improper rim / wheel
mounting, excessive wheel end play or other assembly non-uniformity. It can also
be due to lack of shock absorber control on some suspension types.
To solve cupping problems:
■■ Tires – Correct mismount or balance problem. If ride complaints arise, steer

tires may be rotated to drive or trailer axle.

■■ Vehicle – Diagnose component imbalance condition, i.e., wheel, rim, hub,

brake, drum. Correct as necessary.

FIGURE 6-16

Diagonal Wear — Can be described as localized flat spots worn diagonally
across the tread at approximately 25-35° angles, often repeating around the tread
circumference. For more information, see TMC RP 219A ­publication, page 20.
Diagonal wear is usually caused by bad wheel bearings, toe out, mismounting of tire and wheel assembly to axle, and mismatched duals for size and /
or inflation pressures. It may start as brake skid. Diagonal wear is aggravated
by high speed empty or light load hauls.

FIGURE 6-17

To correct diagonal wear, reverse direction of rotation of the tire. If wear is
excessive, true tire. If the source of trouble is the vehicle, diagnose cause and
correct as needed.
Rapid Shoulder Wear (One Shoulder Only) — Is defined as a tire worn
on the edge of one shoulder, sometimes extending to inner ribs. It can
progress to diagonal wipeout. For more information, see TMC RP 219A
publication, page 22.
This wear condition is usually caused by excessive toe or excessive camber. These conditions can be created by a misaligned or bent axle and can also be caused by loose or worn
wheel bearings.
To correct this type of rapid shoulder wear:
Tires – Change direction of rotation of tire. If shoulder wear is severe, remove and retread.

■■
■■

FIGURE 6-18

Vehicle – Diagnose misalignment and / or mechanical condition and correct.

One-sided wear — Is excessive wear on one side of tire extending from the shoulder towards
the center of the tread. For more information, see TMC RP 219A, page 26.
One-sided wear is usually caused by improper alignment, worn kingpins, loose wheel bearings, excessive camber, excessive axle loads, non-parallel axles, or non-uniform tire and
wheel assembly caused by improper bead seating or bent wheel.
To correct one-sided wear:
■■ Tires – Depending on severity, rotate tires to another axle position or, if worn to minimum
tread depths, submit for possible retreading.
■■

Preventive Maintenance

Vehicle – Diagnose mechanical problem and correct.
18

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OPTIMAAX® for Freightliner Vehicles
SHOCK ABSORBER
NOTE

FIGURE 6-19

It is not necessary to replace shock absorbers in pairs if
only one (1) shock absorber requires replacement.
Hendrickson uses a long service life, premium shock
absorber on all OPTIMAAX suspensions. When the shock
absorber replacement is necessary, Hendrickson recommends that the shock absorbers be replaced with
identical Hendrickson Genuine parts for servicing. Failure
to do so will affect the suspension performance, durability, and will void any applicable w
­ arranty. See vehicle
manufacturer’s applicable publications for other shock
absorber inspection requirements.
Inspection of the shock absorber can be performed by
doing a heat test, and a visual inspection. Replace as
necessary, refer to the Component Replace­ment Section
of this publication.

HEAT TEST
1. Drive the vehicle at moderate speeds on rough road
for minimum of fifteen minutes.
DO NOT GRAB THE SHOCK ABSORBER AS IT COULD POSSIBLY BE HOT AND CAUSE PERSONAL INJURY.

2. Use an infrared thermometer to check the temperature of the shock absorber. This can also
be performed by carefully touching the shock absorber body below the dust cover. Touch the
frame to get an ambient reference, see Figure 6-19. A warm shock absorber is acceptable, a
cold shock absorber should be replaced.
3. To inspect for an internal failure, remove and shake the suspected shock absorber. Listen for
the sound of metal parts rattling inside. Rattling of metal parts can indicate that the shock
absorber has an internal failure and the shock absorber should be replaced.

VISUAL INSPECTION
FIGURE 6-20

Look for these potential problems when doing a visual inspection. Inspect the shock absorbers
fully extended. Replace as necessary.
SHOCK ABSORBER VISUAL INSPECTION - UNACCEPTABLE CONDITIONS

LEAKING VS. MISTING SHOCK ABSORBER VISUAL INSPECTION
The inspection must not be conducted after driving in wet weather or a vehicle wash. The shock
absorber needs to be free from water. Many shock absorbers are often misdiagnosed as failures.
Misting is the process whereby very small amounts of shock absorber fluid evaporate at a high
­operating temperature through the upper seal of the shock absorber. When the “mist” reaches
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Preventive Maintenance

OPTIMAAX® for Freightliner Vehicles
the cooler outside air, it condenses and forms a film on the outside of the shock absorber body.
Misting is perfectly normal and necessary function of the shock absorber. The fluid which evaporates through the seal area helps to lubricate and prolong the life of the seal.
FIGURE 6-21

NOTE

OPTIMAAX systems are equipped with a premium seal
on the shock absorber, however this seal will allow for
misting to appear on the shock absorber body (misting
is not a leak and is considered acceptable).
Inspect the shock absorber fully extended. A shock
absorber that is truly leaking will show signs of fluid
leaking in streams from the upper seal. These streams
can easily be seen, underneath the main body (dust
cover) of the shock absorber. Replace as necessary.

Preventive Maintenance

20

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OPTIMAAX® for Freightliner Vehicles
SECTION 7

Alignment & Adjustments
AXLE ALIGNMENT
Proper alignment is essential for maximum ride quality, performance, and tire service life. The
recommended alignment procedure is described below. This procedure should be performed if
excessive or irregular tire wear is observed, or any time the QUIK‑ALIGN connection is loosened
or removed.
FIGURE 7-1

The QUIK-ALIGN alignment
feature incorporates two
(2) collars that are inserted
into slots located on each
side of the frame hanger.
The outboard collar is
eccentric and inboard is
concentric. The position of
the eccentric collar is controlled by an adjustment
guide, see Figure 7‑1.
Rotating the eccentric collar clockwise or counter
clockwise provides fore
and aft movement of the suspension’s axle. The eccentric collar square hole helps to indicate the
alignment position. The maximum adjustment range is 45° from the twelve o'clock position, see
Figure 7-2.
The QUIK‑ALIGN connection is clamped together with a shear round-head bolt, washers and a prevailing torque heavy hex nut.The shear bolt helps make the QUIK-ALIGN connection tamper resistant.
FIGURE 7-2

INSPECTION
1. Use a work bay with a level surface and free of debris.
PRIOR TO REMOVING OR INSTALLING THE 15 AMP FUSE FROM THE F15 LOCATION, ENSURE ALL
PERSONNEL AND EQUIPMENT ARE CLEAR FROM UNDER THE VEHICLE AND AROUND THE SERVICE
AREA, FAILURE TO DO SO CAN CAUSE SERIOUS PERSONAL INJURY, DEATH, OR PROPERTY DAMAGE.
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Alignment & Adjustments

OPTIMAAX® for Freightliner Vehicles
2. Ensure all personnel and equipment are clear from under the vehicle and around the service
area.
3. Prior to starting the vehicle, remove the 15 AMP Fuse from F15 location, this will allow the
OPTIMAAX axle to lower and prevent the axle from retracting.
4. Start the vehicle. Relax the suspension by slowly moving the vehicle back and forth several
times in straight line without using the brakes. This will slacken or loosen the suspension as
the vehicle is positioned. End with all wheels positioned straight ahead.
5. DO NOT set the vehicle's parking brake.
6. Chock the front wheels of the vehicle.
7. Inspect each set of tires. If equipped with dual wheel set tires, each set must match to a maximum of 1⁄8" tire radius or a maximum of ¾" variation in tire circumference.
NOTE

Since the liftable forward tandem axle will be aligned relative to the drive axle, it is essential
that the drive axle is aligned within the vehicle manufacturer’s specifications prior to the liftable
forward tandem axle alignment.
8. Verify and maintain the air system at full operating pressure.
FIGURE 7-3

9. Verify the vehicle is at the correct ride
height. Correct as necessary, refer to the
to the vehicle manufacturer for proper
instructions.
10. Verify all suspension all components are in
good condition. Repair or replace any worn
or damaged suspension components prior
to proceeding with the alignment process.
11. If alignment equipment is not available,
Use a trammel bar to measure the distance
between the drive axle spindle center to the
liftable forward tandem axle spindle center on the left side of the vehicle (A), see
Figure 7-3.
12. Use a trammel bar, measure the distance
between the drive axle spindle center to the
liftable forward tandem axle spindle center
on the right side of the vehicle (B).
13. Calculate the distance between the two
measurements (A-B).
■■

If the difference is 1⁄ 16" or less, the liftable forward tandem axle alignment is acceptable.
a. Engage the parking brake.
b. Ensure all personnel and equipment are clear from under the vehicle and around
the service area.
c. Install the 15 AMP Fuse into the F15 location.
d. Remove wheel chocks.

■■

Alignment & Adjustments

If the difference is greater than 1⁄ 16", it is necessary to align the liftable forward tandem
axle. Proceed to OPTIMAAX Adjustment.

22

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OPTIMAAX® for Freightliner Vehicles
OPTIMAAX ADJUSTMENT
You will need:
■■
■■
■■
■■

NOTE

1" drive E-20 QUIK-ALIGN Socket (see Special Tools section)
17⁄16" Wrench
½" Square Drive Breaker Bar
Impact wrench capable of 600 foot pounds

The liftable forward tandem axle alignment should be adjusted so the center-line is parallel to the
centerline of the drive axle, see Figure 7-3.
1. Determine which side of the liftable forward tandem axle requires alignment adjustment.
2. Remove and discard QUIK-ALIGN fasteners. Leave the inboard concentric collar and outboard
eccentric collar in place, see Figure 7-1.
HENDRICKSON DOES NOT AUTHORIZE REUSE OF THE SHEAR ROUND BOLT. WHENEVER THE QUIK‑ALIGN
CONNECTION IS DISASSEMBLED, THE EXISTING SHEAR-TYPE BOLT MUST BE REMOVED BY GRINDING
OR ANY OTHER APPROPRIATE METHOD AND DISCARDING THE EXISTING HEX NUT. A NEW SHEAR
ROUND BOLT AND HEX NUT MUST BE INSTALLED AND SHEARED TO ACHIEVE THE PROPER TORQUE AND
CLAMP FORCE. ANYONE WHO ASSEMBLES THE QUIK‑ALIGN CONNECTION (OEM’S, DEALERS, REPAIR
FACILITIES, ETC.) IS RESPONSIBLE FOR THE PROPER INSTALLATION OF THE SHEAR-TYPE BOLT. FAILURE
TO REACH THE REQUIRED TORQUE CAN RESULT IN AN INSUFFICIENT CLAMP FORCE, UNRELIABLE AXLE
ALIGNMENT, INJURY OR PROPERTY DAMAGE.
DO NOT APPLY OR ALLOW ANY TYPE OF LUBRICANT TO CONTACT THE THREADS OF THE SHEAR-TYPE
BOLTS. LUBRICANT WILL REDUCE THE FRICTION BETWEEN THE THREADS OF THE BOLTS AND THE
TORQUE PREVAILING HEAVY HEX NUT. FAILURE OF THE SHEAR-TYPE BOLTS MAY OCCUR.

FIGURE 7-4

FIGURE 7-5

ACCEPTABLE

UNACCEPTABLE

INBOARD

OUTBOARD
Frame Hanger

QUIK-ALIGN
Concentric Collar

/8" Prevailing Torque

7

Heavy Hex Nut

• Not flushed against hanger
• Not within adjustment guides

FIGURE 7-6

UNACCEPTABLE
• Not flushed against hanger
• Tilted bolt

Adjustment
Guides
QUIK-ALIGN
Eccentric Collar

/8" Shear Round
Head Bolt
7

TRI-FUNCTIONAL III
Bushing

3. Install new QUIK-ALIGN fasteners with the shear round head bolt outboard and the hex nut
inboard, see Figure 7-4.
4. Tighten the fasteners tight enough to hold the eccentric flanged collar flush against the
hanger face and within the adjustment guide, but loose enough to permit to the eccentric
collar to rotate freely, see Figure 7-5.
5. Ensure both the eccentric and concentric collars are flush against the hanger.
6. Use a ½" square drive breaker bar to rotate the eccentric collar and ensure both the eccentric
and concentric collars, are aligned and moving simultaneously, see Figure 7.6.
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Alignment & Adjustments

OPTIMAAX® for Freightliner Vehicles
FIGURE 7-7

7. Adjust the axle until the axle is aligned, see Figures 7-7 and 7-8.
NOTE

Ensure axle alignment occurred without compressing the TRI-FUNCTIONAL bushing.
8. Repeat Steps 2 through 7 on the opposite QUIK‑ALIGN connection if necessary, to accurately
complete the alignment of the liftable forward tandem axle.
9. Snug the QUIK‑ALIGN fasteners and recheck alignment, see Figure 7-9.
FIGURE 7-8

FIGURE 7-9

EXCEEDING TORQUE SPECIFICATIONS MAY RESULT IN FASTENER FAILURE OF THE QUIK-ALIGN
CONNECTION.

10. Use a QUIK-ALIGN socket tool (see Special Tools Section of this publication) to tighten the
shear round bolt until the head shears off. Ensure the drive socket fully engages the shear
head to avoid damaging the splines. Hendrickson recommends tightening the shear round
head bolts to shear ( 550 foot pounds torque).
11. Engage the parking brake.
PRIOR TO REMOVING OR INSTALLING THE 15 AMP FUSE FROM THE F15 LOCATION, ENSURE ALL
PERSONNEL AND EQUIPMENT ARE CLEAR FROM UNDER THE VEHICLE AND AROUND THE SERVICE
AREA, FAILURE TO DO SO CAN CAUSE SERIOUS PERSONAL INJURY, DEATH, OR PROPERTY DAMAGE.

12. Ensure all personnel and equipment are clear from under the vehicle and around the service
area. Install the 15 AMP Fuse into the F15 location to raise the OPTIMAAX axle.
13. Remove the wheel chocks.
Alignment & Adjustments

24

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OPTIMAAX® for Freightliner Vehicles
SECTION 8

Component Replacement
FASTENERS
Hendrickson recommends that when servicing the vehicle to replace the removed fasteners with
new equivalent fasteners. Maintain correct torque values at all times. Check torque values as
specified, see Hendrickson’s Torque Specifications section in this publication. If non-Hendrickson
fasteners are used follow torque specifications listed in the vehicle manufacturer’s service manual.

RIDE AIR SPRING
DISASSEMBLY
1. Chock the front wheels.
2. Support the frame of the vehicle at ride height with safety stands.
3. Disconnect the height control linkage assembly from the height control valve arm on the
drive axle, see vehicle manufacturer’s instructions.
PRIOR TO AND DURING DEFLATION AND INFLATION OF THE AIR SUSPENSION SYSTEM, ENSURE ALL
PERSONNEL AND EQUIPMENT ARE CLEAR FROM UNDER THE VEHICLE AND AROUND THE SERVICE
AREA, FAILURE TO DO SO CAN CAUSE SERIOUS PERSONAL INJURY, DEATH, OR PROPERTY DAMAGE.

LIFT AXLE RAPID AUTOMATIC MOVEMENT
LIFT AXLE RAPID, AUTOMATIC MOVEMENT CAN CAUSE SEVERE PERSONAL INJURY OR DEATH.
THE LIFT AXLE CONTROL SYSTEM IS PROGRAMMED TO AUTOMATICALLY:
LOWER THE LIFT AXLE IF –
■■
A LOAD ON THE PRIMARY REAR SUSPENSION IS ABOVE A PRESET VALUE, OR
■■
THE PARKING BRAKE IS ENGAGED, OR
■■
THE IGNITION SWITCH IS OFF, OR
■■
A MAJOR SYSTEM FAULT IS DETECTED
RAISE THE LIFT AXLE IF –
■■
1) THE PARKING BRAKE IS DISENGAGED, AND 2) A LOAD ON THE PRIMARY REAR SUSPENSION
IS BELOW A PRE-SET VALUE.

LIFT AXLE LOADING / UNLOADING
■■ ENSURE ALL PERSONNEL ARE CLEAR OF LIFT AXLE DURING VEHICLE LOADING / UNLOADING AND

OPERATION.

■■ ENGAGE THE PARKING BRAKE DURING VEHICLE LOADING / UNLOADING.

PRIOR TO SERVICE
■■ EXHAUST ALL PRESSURE IN LIFT AXLE AIR SPRINGS AND VEHICLE AIR SYSTEM BEFORE WORKING

ON OR AROUND LIFT AXLE.

■■ REMOVE 15 AMP FUSE FROM F15 LOCATION, REFER TO HENDRICKSON LITERATURE NO.

17730-310.
4. See additional Air Spring Cautions and Warnings in the Important Safety Notice section of
this publication prior to deflating or inflating the air system.

5. Lower the height control valve arm to exhaust the air in the air springs and deflate the rear
suspension per vehicle manufacturer’s instructions.
6. Remove the air line from the air spring.

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Component Replacement

OPTIMAAX® for Freightliner Vehicles
IF THE AIR SPRING IS BEING REMOVED FOR AN ALTERNATE REPAIR, IT IS MANDATORY TO LUBRICATE THE
LOWER AIR SPRING FASTENERS WITH PENETRATING OIL AND REMOVE WITH HAND TOOLS TO PREVENT
DAMAGE TO THE LOWER AIR SPRING MOUNTING STUD. FAILURE TO DO SO CAN CAUSE COMPONENT
DAMAGE AND VOID WARRANTY.
FIGURE 8-1

7. Using HAND TOOLS only,
remove the lower air
spring mounting locknut,
see Figure 8-1. This will
help prevent the air spring
mounting stud from breaking during removal.
8. R e move t h e u p p e r a ir
s p r i n g fa s te n e r s f ro m
the air spring mounting
bracket and the frame, see
Figure 8-1.
9. Remove the air spring.

INSPECTION
1. Inspect the mounting surfaces and lower air spring
mount for any damage. Replace as necessary.

ASSEMBLY
1. Install the air spring between the frame and the trailing arm assembly.
FAILURE TO PRESS THE AIR SPRING AGAINST THE UNDERSIDE OF THE FRAME WHILE TIGHTENING
THE UPPER AIR SPRING BRACKET CAN RESULT IN COMPONENT DAMAGE AND PERSONAL INJURY OR
PROPERTY DAMAGE.

2. Hold the air spring tight against the bottom frame flange and tighten upper air spring mounting fasteners to the frame per vehicle manufacturer’s specifications.
3. Install the air spring lower mounting studs through the mounting bracket hole. Attach the ½"
fasteners to the lower mounting stud of the air spring. Using HAND TOOLS only, tighten the
locknut to 30 ± 5 foot pounds torque, see Figure 8-1.
4. Connect the air line to the air spring, see vehicle manufacturer’s instructions.
5. See additional Air Spring Cautions and Warnings in the Important Safety Notice section of
this publication prior to deflating or inflating the air system.
6. Inflate the suspension by connecting the height control valve linkage to the height control
valve arm, see vehicle manufacturer’s instructions.
7. Remove the frame supports.
8. Remove the wheel chocks.

LIFT AIR SPRING
PRIOR TO AND DURING DEFLATION AND INFLATION OF THE AIR SUSPENSION SYSTEM, ENSURE ALL
PERSONNEL AND EQUIPMENT ARE CLEAR FROM UNDER THE VEHICLE AND AROUND THE SERVICE
AREA, FAILURE TO DO SO CAN CAUSE SERIOUS PERSONAL INJURY, DEATH, OR PROPERTY DAMAGE.

DISASSEMBLY
1. Follow Steps 1 through 6 of Ride Air Spring Disassembly in this section.
2. Loosen lift air spring fasteners from the rear side of the hanger.
Component Replacement

26

17730-309

OPTIMAAX® for Freightliner Vehicles
3. Lower the lift axle into full rebound to access the fasteners that connects the lift air spring to
the paddle.
4. Remove lift air spring.

FIGURE 8-2

ASSEMBLY
1. Install the lift air spring
between the axle beam
paddle and frame hanger.
2. Install the 3⁄ 8" mounting
fasteners through the axle
beam paddle and tighten
to 18 ± 2 foot pounds
torque, see Figure 8-2.
3. Install the ¾" mounting
fasteners to frame hanger
and tighten to 45 ± 5
foot pounds torque, see
Figure 8-2.
4. Follow Steps 4 to 9 of
Ride Air Spring Assembly
in this section.

SHOCK ABSORBER
NOTE

It is not necessary to replace shock absorber in pairs if only one (1) shock absorber requires
replacement.
FIGURE 8-3

DISASSEMBLY
1. Chock the front wheels of the
vehicle.
2. Remove and discard the ¾"
locknut from the upper shock
absorber bracket.
3. Remove and discard the 5⁄8" lower
shock absorber fasteners that
connect to the axle beam assembly, see Figure 8-3.
4. Compress the shock absorber
and slide out from upper mounting bolt.
5. Remove the shock absorber.

ASSEMBLY
1. Install the shock absorber into
the upper shock absorber
bracket. Attach the ¾" upper shock locknut (see Figure 8-3) and tighten to
pounds torque.

188 ± 12 foot

2. Install the lower shock absorber to the axle beam assembly. Attach the lower shock absorber
fasteners and tighten to 170 ± 10 foot pounds torque, see Figure 8-3.
3. Remove the wheel chocks.
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Component Replacement

OPTIMAAX® for Freightliner Vehicles
AXLE BEAM ASSEMBLY
NOTE

Hendrickson recommends when servicing one (1) TRI-FUNCTIONAL bushing or thrust washer that
all TRI-FUNCTIONAL bushings and thrust washers be replaced.

DISASSEMBLY
1. Chock the wheels.
2. Support the frame of the vehicle at ride height with safety stands.
3. Disconnect the height control valve’s leveling valve arm(s) from the rubber grommet, see