chapter 27 bennet

8/10/2019 Chapter 27 Bennet

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Objectives (1 of 2)

Identify the wheel configurations used on heavy-duty trucks.

Explain the difference between standard and wide-base wheel systems and stud- and hub-piloted

mountings. Identify the common types of tire-to-rim hardware

and describe their functions.

Explain the importance of proper matching andassembly of tire and rim hardware.

Outline the safety procedure for handling andservicing wheels and tires.

Describe brake drum mounting configurations.


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Objectives (2 of 2)

Perform wheel runout checks and adjustments.

Properly match tires in dual and tandem mountings.

List the major components of both grease- and oil-lubricated wheel hubs.

Perform bearing and seal service on grease-lubricated front and rear wheel hubs.

Perform bearing and seal service on oil-lubricatedfront and rear wheel hubs.

Perform front and rear bearing adjustment. Describe TMC wheel-end procedure.

Outline the procedure for installing pre-set bearingwheels.


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Cast Spoke Wheels


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Spoke Wheel Duals


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Disc Wheels


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Hub-Piloted Wheel


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Stud-Piloted Wheel


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Wide-base Wheels


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Tires


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Construction of

Bias Ply and Radial Tires


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Tire Size


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Shop Talk

Learn how to identify stud- and hub-piloted

disc wheels: Improper torquing procedure

and sequencing of stud-piloted wheels is a

major cause of wheel failure. With the cone locknut design, a flat washer is

seated directly against the wheel face. The

nonrotating washer prevents galling of thewheel surface.


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Shop Talk

Revolutions per mile data on the drive axle tiresmust be correctly programmed to the chassis databus.

Whenever tires are replaced or swapped on a

vehicle, ensure that you check and reprogram tirerevolutions per mile to the appropriate controller onthe chassis data bus.

This data is used to calculate and broadcast road

speed data to the instrument cluster, engine,transmission, collision warning, and othercontrollers networked to the data bus.


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Shop Talk

Contrary to the beliefs of some truck drivers,

tire pressure cannot be checked with a

hammer.

The only condition a hammer can identify is acompletely deflated tire.

Tire pressures must be checked with a

pressure gauge. In fleets where this is not adrivers responsibility, it must be done by a

technician.


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Shop Talk

Manufacturers of speed

restricted tires, such as the

off-highway lug caution

operators not to exceed the

speed limits and guidelines in

their manuals.

To alert the operator, a decal

located in the cab warns ofthe limitations of speed

restricted tires.


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Shop Talk

Tires are a major fire hazard when trashed

and stored in large quantities.

Once a tire fire has ignited, it can be almost

impossible to extinguish.

Federal and state regulations have made

operators and garages liable for ensuring that

tires are stored and disposed of legally.


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Caution

You cannot learn tire and wheel service

procedure from a book alone.

Before working on tires and wheels make

sure you have received some hands-ontraining.


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Caution

When handling tire assemblies, remember to

lift properly, using your legs rather than your

back.


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Caution

Never raise a vehicle with a jack placed

under a leaf spring.

When the wheel has been raised, use heavy-

duty axle stands placed under the axle anddo not rely on a hydraulic jack alone.


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Shop Talk

The valves used on truck tires are known as

Schrader valves, identical to those used on

cars and bicycles.

It is probably the only common componentfound on all vehicles ranging from a bicycle

to the heaviest off-highway earth moving

equipment.


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Removing Tire Valve Core


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Shop Talk

Disc wheel nuts for right side wheels

generally have right-hand threads, and wheel

nuts for left side wheels usually have left-

hand threads.


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Removing the Tire from a Spoke Wheel


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Removing a Tire from a Disc Wheel


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Caution

Igniting quick start (ether) inside a tire is a

common but dangerous practice used to seat

tire beads.

The explosion that results depends on theproportions of air and ether combined inside

the tire.

Get this mixture wrong and you could injureyourself and others.


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Safety Cage


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Use a Remote In-line Valve

and Gauge When Inflating


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Caution

Watch your fingers and back when installing

tire/rim assemblies onto cast spoke wheels.

It is good practice to wear gloves, and lifting

with the tire/rim behind you is easier on yourback.


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Caution

To check and tighten the inner wheel torque, first

loosen the outer wheel nuts several turns and

tighten the inner nuts, then retighten the outer nuts.

To avoid losing the seating of the outer wheel when

checking the inner wheel torque, loosen alternate

outer nuts, tighten the inner nuts, and retighten the

outer nuts. Then loosen the remaining outer nuts,

tighten inner nuts, and retighten the outer nuts.

OEMs suggest that disc wheels require weekly

inspects and torque checks.


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Torque Sequence for Disc Wheels

U i S


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Using a Square to

Check Dual Tire Matching


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Difference in Tire Size

Typical Dual Mounting


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Typical Dual Mounting

of Cast Spoke Wheel


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Lip-Type Seals

Typical Metal encased


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Typical Metal-encased

Lip-type Seals

Sh T lk


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Shop Talk

If pulling more than one wheel, be sure tokeep all of the components of each wheel

together and separate from the other wheels.

C ti


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Caution

Never allow a bearing roller to be spun bycompressed air because the friction that

results can damage the hard surfaced

contact areas.

C ti


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Caution

Never use oxy-acetylene torches to heataluminum hubs.

This type of localized heat can weaken and

often destroy the aluminum. If an oven is not available, you should

replace the hub and bearing assembly as a

unit.

Sh T lk


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Shop Talk

To ease the installation of the bearing cupinto the hub, the cup can be cooled (by dry

ice or in a freezer), a procedure that stresses

both the bearing cup and hub more evenly. Aluminum hubs are required to be heated in

an oven to get the cup to drop into place.

C ti


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Caution

Never pack wet bearings with grease.

Grease coated wheel bearings inhibit the

ability of gear lube to properly lubricate the

bearing assembly.

C ti


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Caution

Never hammer or use a punch directly onany part of a seal.

Force must be applied evenly around the

outer edge to avoid cocking the seal. Wheel seals are expensive. Failed wheel

seals are more expensive because of the

labor required to replace them!

Shop Talk


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Shop Talk

The reason dry bearings are seldom used oncurrent equipment is that grease does not

lubricate as effectively as gear oil.

Gear oil has a much wider temperatureoperating range than grease.

Caution


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Caution

Avoid using brass drifts to drive out wheelseals if you plan on reusing the bearing

brass particulate is difficult to remove from a

bearing.

Unitized Hub


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Unitized Hub

Bearing Setting Hardware


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Bearing Setting Hardware

Shop Talk


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Shop Talk

Wheel seal replacements are routine service facilityactivities.

Because of the cost of seals, trainee technicians do

not commonly practice seal replacement in a

training environment.

The first couple of times you replace wheel seals in

a real-world setting, read the instructions and ask

questions. The bottom line is that if you experiencecomeback failures after replacing wheel seals, your

days as a truck technician will not last long.


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Dynamic Balance Weight Chart


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Dynamic Balance Weight Chart

Summary (1 of 7)


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Summary (1 of 7)

Wheels and tires must be properly inspectedduring daily driver inspections and on

preventive maintenance schedules.

Improperly mounted, matched, aligned, orinflated tires create potentially dangerous on-

road situations.

Wheel bearings and wheel seals are key tokeeping the wheel assemblies turning

smoothly and safely.

Summary (2 of 7)


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Summary (2 of 7)

The rim supports the tire. Three general categories of tread design are used

on trucks. Rib tread, general duty lugs, and high-traction lugs

These thread designs are used on bias ply and radialtires.

One wide-base wheel and tire can replace atraditional dual wheel assembly. Wide-base wheels are categorized as high flotation,

super single, wide body, duplex, or jumbo wheels. Compared to steel dual wheel assemblies,

aluminum wide-base wheels and tires aresignificantly lighter in weight.

Summary (3 of 7)


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Summary (3 of 7)

Three basic types of wheels are used in truckapplications: cast spoke, stud-mounted disc, and

hub-mounted disc.

Tires should not be mismatched.

Mismatching includes the mixing of nominal tire sizes

and tread designs on a chassis. It is especially

important that a set of duals never be mismatched.

The tire body and belt material can be constructed

of rayon, nylon, polyester, fiberglass, steel, or the

newest synthetic rubber compounds.

Summary (4 of 7)


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Summary (4 of 7)

All tires (new and retread) sold in the United Statesand Canada must have a DOT number cured into

the lower sidewall on one side of the tire.

Proper tire care and maintenance is second only to

fuel mileage in overall cost per mile of truckoperation.

Improper loading can cause the tires on one side of

the truck or trailer to carry a greater percentage of

the load than those on the other side.

Summary (5 of 7)


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Summary (5 of 7)

Excessive heat produced by running avehicle at higher-than-rated speeds will

shorten tire life.

Wheel balance is the equal distribution ofweight in a wheel with the tire mounted.

Improper wheel bearing adjustment can

result in looseness in the bearings, steering

problems, or serious wheel-off incidents.

Summary (6 of 7)


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Summary (6 of 7)

Technicians should learn and always use theTMC method of adjusting bearings when

working on wheel ends with adjustable

bearings. Preset axle hubs such as the ConMet PreSet

and the Spicer Dana UHS eliminate the need

for the technician to adjust wheel bearings.

These wheel hubs are installed on the axle

and torque to a specified value.

Summary (7 of 7)


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Summary (7 of 7)

Two general categories of wheel seals areused on trucks today.

Lip-type seals and unitized seal assemblies

Wheel seals should always be installed usingOEM seal drivers to avoid damaging them.

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