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Chapter 27 Wheels and Tires.

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1 Chapter 27 Wheels and Tires

2 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 and assembly of tire and rim hardware. Outline the safety procedure for handling and servicing wheels and tires. Describe brake drum mounting configurations.

3 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-lubricated front and rear wheel hubs. Perform front and rear bearing adjustment. Describe TMC wheel-end procedure. Outline the procedure for installing pre-set bearing wheels.

4 Cast Spoke Wheels

5 Spoke Wheel Duals

6 Disc Wheels

7 Hub-Piloted Wheel

8 Stud-Piloted Wheel

9 Wide-base Wheels

10 Tires

11 Construction of Bias Ply and Radial Tires

12 Tire Size

13 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 the wheel surface.

14 Shop Talk Revolutions per mile data on the drive axle tires must be correctly programmed to the chassis data bus. Whenever tires are replaced or swapped on a vehicle, ensure that you check and reprogram tire revolutions per mile to the appropriate controller on the chassis data bus. This data is used to calculate and broadcast road speed data to the instrument cluster, engine, transmission, collision warning, and other controllers networked to the data bus.

15 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 a completely deflated tire. Tire pressures must be checked with a pressure gauge. In fleets where this is not a driver’s responsibility, it must be done by a technician.

16 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 of the limitations of speed restricted tires.

17 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.

18 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-on training.

19 Caution When handling tire assemblies, remember to lift properly, using your legs rather than your back.

20 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 and do not rely on a hydraulic jack alone.

21 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 component found on all vehicles ranging from a bicycle to the heaviest off-highway earth moving equipment.

22 Removing Tire Valve Core

23 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.

24 Removing the Tire from a Spoke Wheel

25 Removing a Tire from a Disc Wheel

26 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 the proportions of air and ether combined inside the tire. Get this mixture wrong and you could injure yourself and others.

27 Safety Cage

28 Use a Remote In-line Valve and Gauge When Inflating

29 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 your back.

30 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.

31 Torque Sequence for Disc Wheels

32 Using a Square to Check Dual Tire Matching

33 Difference in Tire Size

34 Typical Dual Mounting of Cast Spoke Wheel

35 Lip-Type Seals

36 Typical Metal-encased Lip-type Seals

37 Shop Talk If pulling more than one wheel, be sure to keep all of the components of each wheel together and separate from the other wheels.

38 Caution Never allow a bearing roller to be spun by compressed air because the friction that results can damage the hard surfaced contact areas.

39 Caution Never use oxy-acetylene torches to heat aluminum 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.

40 Shop Talk To ease the installation of the bearing cup into 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.

41 Caution Never pack wet bearings with grease.
Grease coated wheel bearings inhibit the ability of gear lube to properly lubricate the bearing assembly.

42 Caution Never hammer or use a punch directly on any 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!

43 Shop Talk The reason dry bearings are seldom used on current equipment is that grease does not lubricate as effectively as gear oil. Gear oil has a much wider temperature operating range than grease.

44 Caution Avoid using brass drifts to drive out wheel seals if you plan on reusing the bearing— brass particulate is difficult to remove from a bearing.

45 Unitized Hub

46 Bearing Setting Hardware

47 Shop Talk Wheel seal replacements are routine service facility activities. 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 experience comeback failures after replacing wheel seals, your days as a truck technician will not last long.

48 Driving the Seal Into the Hub

49 Dynamic Balance Weight Chart

50 Summary (1 of 7) Wheels and tires must be properly inspected during daily driver inspections and on preventive maintenance schedules. Improperly mounted, matched, aligned, or inflated tires create potentially dangerous on-road situations. Wheel bearings and wheel seals are key to keeping the wheel assemblies turning smoothly and safely.

51 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 radial tires. One wide-base wheel and tire can replace a traditional 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 are significantly lighter in weight.

52 Summary (3 of 7) Three basic types of wheels are used in truck applications: 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.

53 Summary (4 of 7) All tires (new and retread) sold in the United States and 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 truck operation. 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.

54 Summary (5 of 7) Excessive heat produced by running a vehicle at higher-than-rated speeds will shorten tire life. Wheel balance is the equal distribution of weight 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.

55 Summary (6 of 7) Technicians should learn and always use the TMC 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.

56 Summary (7 of 7) Two general categories of wheel seals are used on trucks today. Lip-type seals and unitized seal assemblies Wheel seals should always be installed using OEM seal drivers to avoid damaging them.

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