■■
■■

Overall Fast Wear (miles per 32nd)
Feather Wear
Cupping

■■
■■
■■

Diagonal Wear
Rapid Shoulder Wear (one shoulder only)
One-Sided Wear

FIGURE 7–12

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 Literature No. RP 219 (“Radial Tire Wear Conditions and Causes”). For information on how
to accurately measure and record tire rates, see TMC Literature No. RP 230 (“Tire Test Procedures
for Tread Wear, Serviceability, and Fuel Economy”).
FIGURE 7–13

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 misalignment 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 Literature No. RP 219 (“Radial Tire Wear Conditions and
Causes”), 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.
FIGURE 7–14

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
Literature No. RP 219 (“Radial Tire Wear Conditions
and Causes”), 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 stabilizer control on some
suspension types.

Preventive Maintenance

28

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COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
To solve cupping problems:
■■

■■

Tires – Correct mis-mount 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 7–15

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 Literature
No. RP 219 (“Radial Tire Wear Conditions and Causes”), page 20.
Diagonal wear is usually caused by bad wheel bearings, toe-out, mimounting 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 7–16

To correct diagonal wear, reverse direction of rotation of the tire. If wear
is excessive, true or retread. 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 Literature
No. RP 219 (“Radial Tire Wear Conditions and Causes”), 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:

FIGURE 7–17

■■

Tires – Change direction of rotation of tire. If shoulder wear is severe, remove and retread

■■

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 Literature No. RP 219 (“Radial Tire Wear
Conditions and Causes”), 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:
■■

■■

TP–H633

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

29

Preventive Maintenance

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
SECTION 8

Component Replacement
STEERING KNUCKLE DISASSEMBLY
1. Chock the rear wheels of the vehicle.
2. Set the parking brake.
3. Raise the lift axle and support with jack stands.
4. Remove the wheel and hub assembly.
5. Remove the brake components from the steering knuckle.
6. Remove the tie rod assembly (See Figure 8–1).
FIGURE 8–1

7. Remove the bolts that connect upper
kingpin assembly to the steering knuckle.
REMOVAL OF THE BOLTS WILL ALLOW THE
STEERING KNUCKLE TO SEPARATE FROM THE
AXLE WHICH CAN RESULT IN COMPONENT
DAMAGE AND/OR PERSONAL INJURY. STEERING
KNUCKLE MUST BE SUPPORTED BEFORE
REMOVAL OF THE TWO BOLTS.

SERVICE HINT

Remove the grease zerks from the knuckle
assemblies. This will allow the knuckle assemblies to freely slide up and down the kingpins without creating back pressure.
8. Remove the steering knuckle from the kingpin by sliding it down the kingpin.
9. Remove the upper kingpin assembly from the axle by sliding it up and off the kingpin.

KINGPIN PREPARATION AND MEASUREMENT
CLEANING THE GROUND OR POLISHED PARTS
■■

Use a cleaning solvent to clean ground or polished parts and surfaces. DO NOT USE
GASOLINE

DO NOT USE HOT SOLUTION TANKS OR WATER AND ALKALINE SOLUTIONS TO CLEAN GROUND OR
POLISHED PARTS. DAMAGE TO THE PARTS WILL RESULT.

CLEANING THE ROUGH PARTS
■■

Rough parts can be cleaned with the ground or polished parts. Rough parts can also be
cleaned in hot solution tanks with a weak alkaline solution. The parts must remain in the
hot solution tanks until they are completely cleaned and heated.

DRYING THE CLEANED PARTS
■■

Component Replacement

Parts must be dried immediately after cleaning. Dry the parts with clean paper towels, clean
rags or compressed air. DO NOT dry bearings by spinning with compressed air. Damage to
the bearings will result.

30

TP–H633

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
PREVENTING CORROSION ON CLEANED PARTS
■■

Apply a light coating of oil to all cleaned and dried parts that are going to be reused. DO
NOT apply oil to the brake lining or the brake drums. If parts are to be stored, apply an effective rust inhibitor to all surfaces.

TO HELP PREVENT SERIOUS EYE INJURY, ALWAYS WEAR PROPER EYE PROTECTION WHEN YOU
PERFORM VEHICLE MAINTENANCE OR SERVICE.
SOLVENT CLEANERS CAN BE FLAMMABLE, POISONOUS AND CAUSE BURNS. TO HELP AVOID
SERIOUS PERSONAL INJURY, CAREFULLY FOLLOW THE MANUFACTURER’S PRODUCT INSTRUCTIONS/
GUIDELINES AND THE FOLLOWING PROCEDURES:
1. WEAR PROPER EYE PROTECTION.
2. WEAR PROTECTIVE CLOTHING.
3. WORK IN A WELL-VENTILATED AREA.
4. DO NOT USE GASOLINE, SOLVENTS OR OTHER MATERIALS THAT CONTAIN GASOLINE THAT CAN
EXPLODE.
HOT SOLUTION TANKS OR ALKALINE SOLUTIONS MUST BE USED CORRECTLY. FOLLOW THE
MANUFACTURER’S RECOMMENDED INSTRUCTIONS AND GUIDELINES CAREFULLY TO HELP PREVENT
PERSONAL ACCIDENT OR INJURY.

1. Prepare and polish the kingpin by removing all grease and excess debris using a fine grit
(220 grit or higher) emery cloth and parts solvent, see Figures 8–2 through 8–5.
FIGURE 8–2

FIGURE 8–3

FIGURE 8–4

FIGURE 8–5

2. Inspect the kingpin for wear or damage. Use a micrometer, measure the upper and lower
kingpin in two locations. Positions must be 90 degrees (perpendicular) from each other,
see Figures 8–6 through 8–9.
3. If the kingpin diameter is less than 1.802", kingpin replacement may be necessary.

TP–H633

31

Component Replacement

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
FIGURE 8–6

FIGURE 8–7

FIGURE 8–8

FIGURE 8–9

FABRICATED KNUCKLE KINGPIN BUSHING
YOU WILL NEED:
■■

A hydraulic shop press with a minimum forcing capacity of 5 tons

BEFORE APPLYING HYDRAULIC PRESSURE TO ANY TOOLING SET-UP, ALWAYS CHECK TO ENSURE THE
PRESS PLATE, ADAPTERS AND COMPONENTS BEING WORKED ON ARE POSITIONED PROPERLY, I.E.
“IN LINE” WITH THE RAM OF THE PRESS. IMPROPER POSITIONING CAN CAUSE PERSONAL INJURY
AND/OR COMPONENT DAMAGE.
FIGURE 8–10

The kingpin bushing housing on a fabricated knuckle includes
pre-reamed bushings and seals.

KINGPIN BUSHING REMOVAL
1. Install the steering knuckle assembly or upper kingpin connection in the press. Ensure is securely supported on the
prior to applying hydraulic pressure to press out the bushing.
2. Remove worn kingpin bushing housing.
3. Install the new kingpin bushing housing (refer to Figure 8–10) from the machined side
(axle side) of the steering knuckle and upper kingpin connection. Ensure that the kingpin
bushing housing is tight against the machined surface, see Figures 8–11 through 8–13.
FIGURE 8–11

FIGURE 8–12

FIGURE 8–13

Press

Machined
Surface

Kingpin
Housing

Special Tools

32

TP–H633

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
CAST KNUCKLE KINGPIN BUSHING REMOVAL
YOU WILL NEED:
■■

A hydraulic shop press with a minimum forcing capacity of 2.5 tons (minimum press
capacity of 5,000 psi or use an arbor press)

BEFORE APPLYING HYDRAULIC PRESSURE TO ANY TOOLING SET-UP, ALWAYS CHECK TO BE SURE
THE PRESS PLATE, ADAPTERS AND COMPONENTS BEING WORKED ON ARE POSITIONED PROPERLY,
I.E. “IN LINE” WITH THE RAM. IMPROPER POSITIONING CAN CAUSE PERSONAL INJURY AND/OR
COMPONENT DAMAGE.
FIGURE 8–14

1. Remove the grease cap retaining ring.
2. Install the steering knuckle upside down in
press. Be sure to support the steering knuckle
assembly so that it sits in–line with the press
(See Figure 8–14).
3. Use the grease cap to press out the kingpin
bushing and seal. Remove the grease zerk in
the grease cap or use a hollow driver, to press
out the kingpin bushing.
4. Use the same procedure to remove the kingpin
bushing in the upper kingpin connection.
5. Clean the parts and then inspect before
reassembling.

CAST KNUCKLE BORE MEASUREMENT
Complete the following steering knuckle bore inspection and the measurement instructions
prior to installing the kingpin bushing.
1. Measure the upper knuckle bore inside diameter at two locations. Always use an inside
micrometer or a telescoping gauge when taking a knuckle bore measurement. Some outof- roundness at the top and bottom of the bore edges is acceptable. The steering knuckle
bore diameter is 1.938" ± 0.003".
2. Measure the upper and lower bore in two positions and at two locations. The two positions
must be 90 degrees opposed from each other, see Figures 8–15 through 8–17. If the
average measurement is more than the knuckle bore maximum diameter specification,
replace the knuckle.
FIGURE 8–15

TP–H633

FIGURE 8–16

33

FIGURE 8–17

Special Tools

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
CAST KNUCKLE KINGPIN BUSHING REAMING
YOU WILL NEED:
■■

A hydraulic shop press with a minimum forcing capacity of 5 tons

BEFORE APPLYING HYDRAULIC PRESSURE TO ANY TOOLING SET-UP, ALWAYS CHECK TO BE SURE
THE PRESS PLATE, ADAPTERS AND COMPONENTS BEING WORKED ON ARE POSITIONED PROPERLY,
I.E. “IN LINE” WITH THE RAM. IMPROPER POSITIONING CAN CAUSE PERSONAL INJURY AND/OR
COMPONENT DAMAGE.

1. Install the steering knuckle assembly, steering arm or upper kingpin connection in the press.
2. Always install the kingpin bushing from the machined side (axle side) of the steering
knuckle using a bushing driver. Press in bushing to a depth of no less than 15⁄64" (0.236") or
6 millimeters and no more than 5⁄16" (0.32") or 8 millimeters, see Figures 8–18 and 8–19.
3. Following this procedure it is necessary to ream the kingpin bushings to fit the kingpins, see
Kingpin Bushing Reaming Instructions in this section.
FIGURE 8–18

FIGURE 8–19

KINGPIN BUSHING REAMING
REAM THE KINGPIN BUSHINGS WITH AN ADJUSTABLE STRAIGHT FLUTE REAMER. DO NOT HONE OR
BURNISH THE KINGPIN BUSHINGS. HONING OR BURNISHING WILL DAMAGE THE BUSHINGS AND
WILL VOID APPLICABLE WARRANTIES.
WHEN INSTALLING STEERING KNUCKLE COMPONENTS IN A VICE, IT IS NECESSARY TO PROTECT THE
MACHINED SURFACES FROM GOUGES AND/OR MARRING BY USING BRASS JAWS. FAILURE TO DO
SO CAN CAUSE PREMATURE PART DAMAGE, DAMAGE TO THE STEERING KNUCKLE COMPONENTS,
ADVERSE VEHICLE HANDLING, PERSONAL INJURY OR PROPERTY DAMAGE AND WILL VOID
APPLICABLE WARRANTIES.

1. Install the steering knuckle assembly in a vise with brass jaws.
SERVICE HINT

It is acceptable to mount the knuckle components in a vise either vertically or horizontally when
performing the reaming procedure.
2. Install the reamer into the steering knuckle until the blades touch the kingpin bushing.
3. Rotate the reamer smoothly with light downward pressure. DO NOT apply too much
pressure, see Figure 8–20 and 8–21.

Special Tools

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TP–H633

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
FIGURE 8–20

FIGURE 8–21

4. Slide the reamer out of the bottom of the steering knuckle assembly. If it is necessary to
remove the reamer from the top, rotate the reamer opposite of the cutting rotation.
5. Clean and remove all bearing material from the knuckle assembly. Be sure to remove material from the grease channels and dimples.
6. Clean the 5/8" brake backing plate bolts with a wire wheel and run a tap through the
threads of the steering knuckle / upper kingpin connection. Flush out with brake cleaner
and dry with compressed air.
7. Repeat Steps 1 through 6 to the upper kingpin connection.
PRIOR TO INSTALLATION ENSURE THAT ALL RESIDUAL LOCTITE MATERIAL IS REMOVED FROM THE
MOUNTING BOLTS AND THE THREADED HOLES IN THE UPPER KINGPIN CONNECTION, AND NEW
LOCTITE 277 OR EQUIVALENT IS APPLIED TO HELP ENSURE THAT THE BOLTS SUSTAIN THE PROPER
TORQUE REQUIREMENT. FAILURE TO DO SO CAN CAUSE ADVERSE VEHICLE HANDLING RESULTING IN
PERSONAL INJURY OR PROPERTY DAMAGE.
FIGURE 8–22

NOTE

FIGURE 8–23

The Hendrickson Genuine
Part socket head cap screw
(Part Number: 6110C125H4A8)
comes with a pre-applied Loctite
compound.
8. I n s t a l l t h e s t e e r i n g
knuckle and upper kingpin
connection on the kingpin.
9. Check for the proper fit
by ro ta t i n g t h e k nu c k l e
assembly back and forth
to verify there is no binding
on the kingpin, see Figures
8–22 and 8–23.
10. If the bushing is too tight, repeat Steps 1 though 9 until the proper clearance is achieved.

TP–H633

35

Special Tools

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
KINGPIN SEAL INSTALLATION
1. Place the steering knuckle in a vise with brass jaws or place on a suitable workbench.
The steering knuckle will have the machined surface facing up (axle side up) (See Figure
8–24).
2. Lay the kingpin seal into the bore of the steering knuckle. The seal lip should face outward
(toward the axle) (See Figure 8–25).
3. Use a bushing driver tool to press the seal firmly into the steering knuckle.
4. Install the kingpin seal until it makes contact with the kingpin bushing.
5. Repeat Steps 1 through 4 on the upper kingpin connection.
FIGURE 8–24

FIGURE 8–25
Lay the kingpin seal into the bore of the
steering knuckle. The lip should face
outward, toward the axle.

STEERING KNUCKLE

Machined
Surface up

STEERING KNUCKLE ASSEMBLY
After replacing the kingpin bushings, it is necessary to reassemble the steering knuckle
assemblies.
1. Install the thrust bearing on the lower kingpin, so the top side is up (the thrust bearing
may be stamped TOP or the black seal will designate the top side), when the axle is in the
operating position.
2. Pack the bearing dimples with multipurpose grease (NLGI Grade 2).
3. Install the steering knuckle assembly on the kingpin. It will be necessary to support the
steering knuckle assembly with a bottle jack and a block of wood under the steering
knuckle assembly.
SERVICE HINT

The easiest way to install the knuckle is with the grease cap not installed in the steering knuckle
assemblies. In this manner, it does not create back pressure. The assembly can then freely slide
up and down on the kingpin.
FIGURE 8–26

4. Raise the bottle jack so that there is no free
play between the steering knuckle, thrust
bearing and the bottom of the axle.
5. Install the upper kingpin connection on the
upper kingpin (See Figure 8–26).
6. Install the left and right brake backing plate
bolts finger tight. These are for guide purposes
only.
NOTE

Two guide studs may be substituted in place of the
brake backing plate bolts.
7. Install the two new socket head cap screws until they are finger tight.

Special Tools

36

TP–H633

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
8. Apply slight upward pressure on the upper kingpin connection.
FIGURE 8–27

9. Insert feeler gauges between the upper kingpin
connection and the top of the axle. Check
the clearance between the upper kingpin
connection and the top of the axle (See Figure
8–27).
10. Remove the brake backing plate bolts and
socket head cap screws (See Figure 8–26).
11. Remove the upper kingpin connection.
12. Install the appropriate number of shims to
achieve 0.008" to 0.011" clearance between the upper kingpin connection and the top of
the axle.
EXAMPLE

If 0.050" clearance were measured, 0.040" shims would be required to obtain the required
0.008" to 0.011" clearance.
13. Install the upper kingpin connection onto the kingpin.
14. Slide two 0.010" feeler gauges on each side of the kingpin between the axle and the upper
kingpin connection.
PRIOR TO INSTALLATION ENSURE THAT ALL RESIDUAL LOCTITE MATERIAL IS REMOVED FROM THE
MOUNTING BOLTS AND THE THREADED HOLES IN THE UPPER KINGPIN CONNECTION, AND NEW
LOCTITE 277 OR EQUIVALENT IS APPLIED TO HELP ENSURE THAT THE BOLTS SUSTAIN THE PROPER
TORQUE REQUIREMENT. FAILURE TO DO SO CAN CAUSE ADVERSE VEHICLE HANDLING RESULTING IN
PERSONAL INJURY OR PROPERTY DAMAGE.

15. Install the socket head cap screws and tighten. Refer to torque specifications section in this
publication.
NOTE

Apply Locktite to the Hendrickson Genuine Part socket head cap screws (Part Number:
R–6110C125H4H8).
16. Once the final torque of the socket cap screws has been obtained, remove the two 0.010"
feeler gauges and lower the bottle jack. Check the remaining bolt holes to ensure that the
bolts will thread in.
FIGURE 8–28

17. Affix a magnetic base dial indicator on the axle
and place the tip of the dial indicator on top
of the upper kingpin connection (See Figure
8–28).
18. Zero the dial indicator.
19. Raise the bottle jack until there is no clearance
between the steering knuckle and the bottom
of the axle.
20. Check the reading on the dial indicator. The
specification for vertical travel on the steering
knuckle assemblies is 0.008" to 0.011".
21. If the clearance is not within the required
specification, repeat Steps 3 through 9 until
the proper clearance is obtained by adding or
removing shims.
22. If the vertical travel is not within the specification, repeat Steps 3 through 16 until the
proper vertical travel is obtained.
TP–H633

37

Special Tools

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
23. Remove the bottle jack to remove the load off the knuckle assembly and continue assembling the wheel ends.
24. Install the tie rod cross tube into the tie rod arm.
25. Compliant Tie Rod – Tighten the mounting bolts. Refer to torque specifications section in
this publication.
Rigid Tie Rod – Tighten the castle nuts to 185 foot pounds torque, then rotate the castle
nut to the next castle slot and install the cotter pin. Tighten bolts. Refer to torque specifications section in this publication.
NOTE

Loctite applied to knuckle assembly bolts is a critical procedure to ensure that these bolts sustain the torque requirement of the kingpin connection.
26. Install new O-rings on the grease caps and lubricate the O-rings with grease.
27. Install grease caps and new retaining rings.

AUXILIARY AXLE BRAKE REPLACEMENT
SUPPORT THE LIFT AXLE PRIOR TO SERVICING
PLACE THE VEHICLE ON A LEVEL FLOOR AND CHOCK THE WHEELS TO HELP PREVENT THE VEHICLE
FROM MOVING. PRIOR TO SERVICING A LIFT AXLE IN THE RAISED POSITION, (1) PROPERLY SUPPORT
THE LIFT AXLE WITH SAFETY STANDS, AND (2) RELEASE ALL AIR PRESSURE IN THE LIFT AXLE AIR
SPRINGS AND RIDE SPRINGS. DO NOT WORK AROUND OR UNDER A RAISED LIFT AXLE SUPPORTED
ONLY WITH FLOOR JACKS OR OTHER LIFTING DEVICES, FAILURE TO DO SO CAN CAUSE DEATH,
PERSONAL INJURY OR DAMAGE TO COMPONENTS.

For replacement brake service kits or If a part is not included in the brake service kit, contact
Hendrickson Customer Service Department at (800) 660‑2843.
1. Chock the rear wheels of the vehicle.
2. Set the parking brake.
3. Raise the lift axle and support with jack stands.
4. Remove wheel, brake drum and axle end components to expose the brake shoes.
FIGURE 8-29

Special Tools

38

TP–H633

COMPOSILITE® SC Steerable Auxiliary Axle Suspension Systems
5. Remove the outer retaining spring and inner retaining spring (See Figure 8–30).
6. Support the lower brake shoe assembly and remove the return spring (See Figure 8–31).
Set parts aside and remove the upper brake shoe.
7. Remove the brake bolts and brake anchor pin. If lock straight target is present, note the
position for proper reassembly location (See Figure 8–32.)
8. Hendrickson replacement brake kits for each specific axle will have the necessary parts to
be replaced. Discard worn or damaged parts.
9. Install brake bolts through the anchor pin. Tightened to

160 foot pounds torque.

10. Install new parts in reverse order from Step 5.
NOTE

When reinstalling the retaining spring, ensure the return spring is completely clipped into the
mounting hole (See Figure 8–33).
ENSURE THE RETURN SPRING IS COMPLETELY CLIPPED INTO THE MOUNTING HOLE. FAILURE TO DO
SO COULD RESULT IN BRAKE FAILURE.
FIGURE 8–30