5/8" Tie

Rod Clamp Locknut
Tightening Torque 68 ± 7 ft. lbs.

8. Check that grease zerks are installed. Replace a damaged grease zerk with a new one.
DO NOT USE THE FOLLOWING ITEMS OR METHODS TO CHECK FOR MOVEMENT OF THE TIE ROD
ASSEMBLY, WHICH CAN CAUSE DAMAGE TO COMPONENTS:
■■
■■

■■

A CROW BAR, PICKLE FORK OR 2 X 4.
ANYTHING OTHER THAN HANDS USED TO GRASP AND ROTATE THE CROSS TUBE ASSEMBLY (CAN
RESULT IN DAMAGE TO THE CROSS TUBE).
EXCESSIVE PRESSURE OR FORCE APPLIED TO THE TIE ROD ENDS OR THE JOINTS OF THE ASSEMBLY.

9. By hand or using a pipe wrench, with jaw protectors to avoid gouging the cross tube, rotate
the cross tube toward the front of the vehicle and then toward the rear. After rotating, center
the cross tube. If the cross tube will not rotate in either direction, replace both tie rod ends,
see Figure 7-5.

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STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles
FIGURE 7-5

10. Position yourself directly below the tie rod end. Using both hands, grab the assembly end as
close to the tie rod end as possible (no more than 6" or 152.4 mm). Apply hand pressure with
reasonable human effort vertically up and down in a push-pull motion several times (using
approximately 50‑100 pounds of force). Check for any movement or looseness at both tie rod
end locations, see Figure 7-6.
11. If there is any movement in the tie rod assembly, install a magnetic based dial indicator on the
tie rod arm, see Figure 7-7.
FIGURE 7-6

FIGURE 7-7

Push up and down in
a push-pull motion to
check any movement
or looseness

12. Set the dial indicator to zero.
13. Apply hand pressure with reasonable
human effort vertically up and down in a push-pull motion several times (using approximately
50‑100 pounds of force). Observe the reading on the dial indicator.
14. If the reading is more than 0.060", replace both tie rod ends at the next service i­nterval.
15. If a tie rod end exhibits ≥ 0.125" of movement by hand, the vehicle should be removed immediately from use and the tie rod end be replaced.
NOTE

According to the Commercial Vehicle Safety Alliance (CVSA), the “out of service” criteria for front
steer axle tie rod assemblies on any commercial vehicle is: Any motion other than rotational
between any linkage member and its attachment point of more than 1⁄8" (3 mm) measured with
hand pressure only. (393.209(d)), (published in the North American Standard Out-of-Service
Criteria Handbook, April 1, 2006.)

CLAMP GROUP RE-TORQUE INTERVAL
1. Clamp group hex bolts and axle collar hex cap bolts must be torqued to specification at
preparation for delivery.
2. Clamp group hex bolts and axle collar hex cap bolts must be re-torqued at 1,000 miles.
3. Thereafter follow the 6 month / 25,000 mile visual inspection and annual re-torque interval.
ENSURE CLAMP GROUP IS ALIGNED PROPERLY PRIOR TO TIGHTENING HARDWARE. FAILURE TO DO SO
CAN CAUSE LOSS OF VEHICLE CONTROL, PROPERTY DAMAGE OR PERSONAL INJURY.

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STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles
FIGURE 7-8

4. Ensure that the clamp group is properly
aligned and the hex bolts are seated in
the axle seat, and the top pad is centered
on the leaf spring, see Figure 7-8.
5. Check for the signs of component or bolt
movement.

FIGURE 7-9

6. If signs of movement are present, disassemble the clamp group fasteners, check
for component wear or damage and
replace as necessary, then install new
clamp group fasteners and repeat Steps
4 through 5.
7. Tighten the clamp group hex bolts
evenly in 100 foot pounds increments to
600 ± 20 foot pounds torque in the
proper pattern to achieve uniform bolt tension, see Figure 7-9.

1" Clamp Group Hex Bolt
Tightening Torque at
the Bolt Head
600 ± 20 ft. lbs.
IMPORTANT
Ensure that Clamp
Group Assembly
is properly aligned

1" Axle Collar Bolt
Tightening Torque
800 ± 20 ft. lbs.

STEERING KNUCKLE
CHECKING VERTICAL END PLAY (UP AND DOWN MOVEMENT)
The operating specification for vertical end play on the steering knuckle is 0.008" to 0.030".
FIGURE 7-10
Ensure the tip of
1. Chock the rear tires to help prevent the
the dial indicator
vehicle from moving.
is on the top of
the upper steering
2. Set the parking brakes.
knuckle (not on
3. Use a jack to raise the vehicle until both
the grease cap)

tires are 1" off the ground.

4. Place a dial indicator on each side of
the axle as follows:
a. Index the wheels slightly (left or
right).
b. Place the magnetic dial indicator
base on the axle, see Figure 7-10.
c. Place the tip of the dial indicator
on the top of the upper steering
knuckle (not on the grease cap).
5. Set the dial indicator to “0” (zero).
6. Lower the jack.
7. If vertical end play is greater than 0.030", or below 0.008" an adjustment of the upper knuckle
is necessary.
8. ■ If the vertical end play is greater than 0.030", add shims until the proper vertical end play
is achieved.
■■

If the vertical end play is less than 0.008", remove shims until the proper vertical end play
is achieved.

9. Retighten the kingpin draw keys to

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18

188 ± 12 foot pounds torque.

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STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles
KINGPIN BUSHING
INSPECTION PROCEDURE (STEERING KNUCKLE LATERAL MOVEMENT)
FIGURE 7-11

FIGURE 7-12

CHECKING UPPER KINGPIN BUSHING

CHECKING LOWER KINGPIN BUSHING

FIGURE 7-13

1. Chock the wheels to help prevent the vehicle
from moving. Set the parking brake.
2. Use a jack to raise the vehicle until the
wheels are off the ground. Support the vehicle with safety stands.
3. CHECKING THE UPPER KINGPIN BUSHING.
Install the base of a dial i­ndicator onto the
axle beam and place the tip against the
steering knuckle, see Figure 7‑11.
4. Set the dial indicator to “0” zero.
5. Move the top of the tire in and out by applying reasonable constant pressure and then
release, see Figure 7-13.
6. Check the reading on the dial indicator. If the
dial indicator moves more than 0.015", the
upper bushing is worn or damaged. Replace
both bushings. Refer to the Kingpin Bushing
replacement procedure in the Component
Replacement Section of this publication.
7. CHECKING THE LOWER KINGPIN BUSHING. Install a dial indicator so that the base is on the axle
and the indicator tip is against the inside of the bottom of the knuckle, see Figure 7-12.
8. Set the dial indicator to “0” zero.
9. Move the bottom of the tire in and out. If the dial indicator moves more than 0.015", the
lower bushing is worn or damaged. Replace both kingpin bushings. Refer to the Component
Replacement Section of this publication.
NOTE

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If one bushing is worn or damaged, it is mandatory to replace both the top and bottom bushings
on that knuckle assembly.

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STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles
SHOCK ABSORBERS
The shock absorbers are not supplied by Hendrickson, although it is a required component.
Hendrickson is not responsible for components supplied by the vehicle manufacturer. For assistance with inspection, maintenance and rebuild instructions see vehicle manufacturer.

TIRE INSPECTION
The leading causes of tire wear are the following, in order of importance:
1.
2.
3.
4.

Tire Pressure
Toe Setting
Thrust Angle
Camber

The following tire Inspection guidelines are based upon Technology & Maintenance Council
(TMC) recommended practices. Any issues regarding irregular tire wear where Hendrickson is
asked for assistance will require tire and alignment maintenance records, reference TMC’s literature numbers RP 219A, RP 230, or RP 642.
Tire wear is normally the best indicator of vehicle alignment condition. If tires are wearing too rapidly or irregularly, alignment corrections may be needed. The tire wear patterns described below
can help isolate specific alignment problems.
The most common conditions of concern are:
■■
■■
■■

FIGURE 7-14

FIGURE 7-15

Overall Fast Wear (Miles per 32nd)
Feather Wear
Rapid Shoulder Wear (One Shoulder Only)

■■
■■
■■

One-Sided Wear
Diagonal Wear
Cupping

Overall Fast Wear — Fast wear can be described as exhibiting a good, but accelerated wear
pattern. It is typically caused by operating conditions, such as mountainous terrain, frequency
and severity of turning, abrasive road surfaces in combination with vehicle configurations and
their attributes-such as power steering, heavy axle loads, high wheel cuts, setback axles, short
wheel base tractors, long wheel base straight trucks. To correct this problem, consult with vehicle
and tire manufacturers when specifying equipment or replacing tires. For more information, see
TMC RP 219A publication, page 11. For information on how to accurately measure and record tire
rates, see TMC RP 230 publication.
Feather wear — Tread ribs or blocks worn so that one side is higher than the other resulting in
step-offs across the tread face. Generally, ribs or blocks exhibit this wear. To spot this problem, do
the following:
With one hand flat on the tread of the tire and a firm down pressure, slide your hand across the
tread of the tire. In one direction, the tire will feel smooth and in the opposite direction there will
be a sharp edge to the tread. Typical causes of feather wear include: excessive side force scrubbing, resulting from conditions of m
­ isalignment such as excessive toe, drive axle misalignment,
worn, missing or damaged suspension components, bent tie rods or other chassis misalignment.
To correct this problem, tires can be rotated to another axle for maximum utilization of remaining
tread. Additionally, diagnose the vehicle itself and correct misalignment condition as required. If
steer tire feathers are in opposite directions, an improper toe condition is most likely the cause.
For more information, see TMC RP 219A publication, page 5.
If feather wear on both steer tires is in the same direction, drive axle or other chassis ­misalignment
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.

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STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles
FIGURE 7-16

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

FIGURE 7-17

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.

■■

Vehicle – Diagnose mechanical problem and correct.

FIGURE 7-18

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 7-19

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.
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.

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STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles

SECTION 8

Alignment & Adjustments
ALIGNMENT DEFINITIONS
FIGURE 8-1

Ackermann steering geometry — The geometry of the four bar
linkage consisting of the front axle, two knuckle assemblies, and tie
rod assembly is designed to provide free rolling of front tire in a
turn. Ackermann geometry is dependent upon the steering axle
track-width and wheelbase of the vehicle. Improper geometry
results in wheel scrub in turns which generally appears as toe wear
on the tire, usually more wear on one side of the vehicle than the
other due to the operational route of the vehicle.
Bump steer (feedback) — The feedback felt through the steering
linkage to the steering wheel when a steer axle tire hits a bump in
the road. This occurs because the axle-end of the drag link and the
axle attachment point of the spring do not travel in parallel circular
arcs as the suspension moves up and down. This condition can
also be caused by trapped air in the power steering system.

FIGURE 8-2

Camber — The angle formed by the inward or outward tilt of the
wheel reference to a vertical line. Camber is positive when the wheel
is tilted outward at the top and is negative when the wheel is tilted
inward at the top.
Excessive positive camber may cause smooth wear on the outer half
of the tire tread. Excessive negative camber may cause wear on the
inner half of the tread. Static-unloaded camber angles are built into
the axle to put the loaded tire perpendicular to the road.

FIGURE 8-3

Alignment & Adjustments

Caster — The forward or rearward tilt of the steering axle kingpin in
reference to a vertical line. The angle is measured in degrees. Caster
is positive when the top of the steering axis is titled rearward and is
negative when the tilt is forward. Proper caster is important for directional stability and returnability. Too much positive caster can cause
shimmy, excessive steering effort and is normally a vehicle performance and handling consideration. Uneven positive caster may
create a steering pull toward the side with the lower caster.This attribute may be used to compensate for crowned roads.

22

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STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles
FIGURE 8-4

Kingpin inclination (KPI) — The inward tilt of the kingpin from the vertical. This front
suspension parameter has a pronounced effect on steering effort and returnability. As
the front wheels are turned around an inclined kingpin, the front of the truck is lifted.
This lifting of the vehicle is experienced as steering effort when the turn is executed and
exhibits itself as recovery force when the steering wheel is released.
Kingpin offset — The distance between the center of the tire patch and intersection of
the kingpin axis with the ground. This parameter of front-end geometry is important in
vehicles without power steering and has a major effect on static steering. If there is no
kingpin offset, the tires must scrub around the center of the pin patch when turned in
a static condition, resulting in higher static steering efforts.
Steering arm — The component that connects the drag link to the axle
knuckle assembly.

FIGURE 8-5

FIGURE 8-7

FIGURE 8-6

Scrub, skew, tram angle or parallelism
— The angle formed by two thrust or
tracking lines of a tandem (or multiple)
axle vehicle. As indicated by the term
“parallelism”, the ideal condition is
when the two thrust lines form a 0°
angle, or are parallel to each other.
Positive skew or tram is when the
distance between the right axle ends is
less than the distance between the left.
Any scrub angle other than 0° will cause
the tandem axles to work against each
other. The steer axle must be turned to
offset the “push” of the tandem axles to
keep the vehicle moving straight ahead.
This causes every tire on the vehicle to “scrub”. Tire wear from tandem scrubbing occurs at
the leading edge of the steer tires in a pattern called “inside / outside” wear, that is, the inside
edge of the left steer tire and the outside edge of the right steer tire will exhibit irregular wear
for example. Additional tire wear may occur on all tandem axle tires.
Thrust angle, tracking, or square — The angle formed by the
centerline of the vehicle frame (geometric centerline) and the
direction that an axle points. As indicated by the term “square”,
the ideal value for the angle is 0° or when the axle centerline is at
90° or perpendicular to the geometric centerline. Thrust or tracking to the right is positive, and to the left is negative.
A steering correction is required to offset the effect of the thrust
angles and keeps the vehicle traveling in a straight line. It results
in a lateral offset between the steer and drive axle tires commonly
referred to as “dog tracking.”
Tie rod arm (ackermann-arm, cross tube arm) — The component that transmits steering forces
between left and right axle knuckle assemblies through the cross tube assembly.

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Alignment & Adjustments

STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles
FIGURE 8-8

Toe-in — Is when the horizontal line intersects in front of the wheels, or the
wheels are closer together in front than in the back. Toe-in is commonly designated as positive, toe-out as negative. Excessive toe-in wears the outside
edge of the tires. Steer axle toe is adjustable to reduce wear to the leading
edge of the tire and also to avoid road wander. Toe is adjusted in a static,
unloaded condition so that the tires will run in a straight line under a dynamic,
loaded condition.

FIGURE 8-9

Toe-out — Is when the horizontal lines intersect behind the wheels, or the
wheels are closer together in back than in front. Toe-in is commonly designated as positive, toe-out as negative. Excessive toe-out wears the inside
edge of the tires. Steer axle toe is adjustable to reduce wear to the leading
edge of the tire and also to avoid road wander. Toe is adjusted in a static,
unloaded condition so that the tires will run in a straight line under a dynamic,
loaded condition.

FIGURE 8-10

Toe-out on turns — (See Ackermann Geometry). Excessive turning angles
such as those encountered in pickup and delivery operations may contribute
to premature tire wear. Be advised that the greater turning angles, the more
that toe and camber change. If you have any doubt regarding the optimum
turning angles for your operation, contact the vehicle’s manufacturer, axle
OEM, tire OEM and alignment equipment manufacturer for advice.
Total toe — The angle formed by two horizontal lines through the planes
of two wheels. Steer axle toe is adjustable to reduce wear to the leading
edge of the tire and also to avoid road wander. Toe is adjusted in a static,
unloaded condition so that the tires will run in a straight line under a
dynamic, loaded condition.

INSPECTION PRIOR TO ALIGNMENT
WHEELS AND TIRES
Examine the following items:
■■

The tires are inflated to the manufacturer’s specified tire pressure.

■■

The steer axle tires are the same size and type.

■■

The lug nuts are tightened to manufacturer’s specified torque.

■■

The wheels are balanced.

■■

The wheels and tires are free of excessive wear and damage.

■■

Wheel bearing end play is within OEM specification.

FRONT SUSPENSION
Inspect the following:

Alignment & Adjustments

■■

All fasteners are installed and tightened to the specified torque. See Torque Specification
Section of this publication.

■■

Leaf springs are free of wear or damage.
24

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STEERTEK NXT High Capacity Steer Axle System for Autocar® ACX-XPEDITOR™ Vehicles
■■

Shock absorbers are free of wear and damage.