Chapter 66

1. Chapter 66 Tire, Wheel, and Wheel Bearing Service

2. Contents • Tire, wheel, and wheel bearing diagnosis • Wheel cover removal and installation • Tire maintenance • Measuring tire and wheel runout • Wheel balance • Mounting and dismounting tires • Tire puncture repair • Wheel bearing service

3. Tire, Wheel, and Wheel Bearing Diagnosis Problems usually show up as vibrations, abnormal tread wear patterns, steering wheel pull, abnormal noises,and other symptoms

4. Diagnosing Tire Problems • Inspect the tires for problems • Check both sidewalls and the tread area • If necessary, road test the vehicle to verify the customer complaint • Make sure the symptoms are not being caused by steering, suspension, or front wheel alignment problems

5. Inspecting the Tires Wiggle the tire to check for dry, rough, or loose wheel bearings

6. Tire Impact Damage Typical damage found on used tires

7. Tire Wear Patterns

8. Tire Inflation Problems • Correct tire inflation is important to the service life of a tire • assures the full tire tread contacts the road • Most tires have a recommended cold inflation pressure of 1 to 3 pounds-per-square inch (psi) below the maximum listed air pressure. • Under inflation • wears the outer edges of the tread • sidewalls flex, building up heat • Overinflation • wears the center of the tread • produces a rough ride

9. Tire Inflation Pressure

10. Load Index • Load index indicates the maximum load capacity each tire is designed to support. Like speed ratings, assume near perfect operating conditions to obtain the ratings listed in the table on the left.

11. Tire Vibration Problems • When one of the front tires is vibrating, it may be felt in the steering wheel • When one of the rear tires is vibrating, it will be felt in the center and rear of the car

12. Causes of Tire Vibration

13. Tire Noise • Thumping sound caused by ply separation • Whine due to abnormal tread wear • When these noises occur, inspect the tire for an out-of-round condition or tread cupping • these conditions require replacement

14. Wheel Bearing Noise • Produced by a dry, worn wheel bearing • When balls or rollers are damaged from lack of lubrication, they may emit a humming or growling sound • Checking the bearings: • raise the vehicle on a lift • rotate the tire by hand • feel and listen for bearing roughness • wiggle the tire to check for looseness

15. Wheel Cover Removal and Installation

16. Wheel Cover Removal Pry between the wheel and coverat four alternating points

17. Wheel Cover Installation Hold the wheel cover in place with the valve stem sticking through the cover

18. Tire Maintenance • Maintenance procedures include periodic inspection, inflation pressure checks, and tire rotation • These maintenance steps help ensure safety and longer tire life

19. Checking Tire Inflation Pressure • Remove the valve stem cap • Press the tire gauge squarely over the stem • Compare the reading to the maximum pressure printed on the tire’s sidewall or in the operator’s manual • Adjust the pressure as necessary • Reinstall the cap

20. Tire Service Tools

21. Rotating Tires • Ensures maximum tire life • The front and rear tires wear differently • Rotation helps even out tire wear • Tires are rotated at specific intervals, such as every 3000 miles (4827 km)

22. Tire Rotation Patterns BIAS TIRES RADIAL TIRES

23. Torquing Lug Nuts • Torque is very important, especially on vehicles with mag wheels and lightweight hubs • Overtorquing can cause wheel and hub distortion or brake pulsation • Undertorquing might allow the lug nuts to loosen and the wheel to fall off

24. Torquing Lug Nuts Torque the nuts to specifications in a crisscross pattern

25. Measuring Tire and Wheel Runout • Tire runout • caused by ply separation or manufacturing defect • Wheel runout • caused by impact damage or incorrect welding of the spider and rim

26. Lateral Runout • Side-to-side movement of a wheel or tire • Maximum for a tire • 0.090" (2.0 mm) • Maximum for a wheel • 0.045" (1.0 mm)

27. Measuring Lateral Runout • Mount a dial indicator with the stem against the sidewall and side of the rim • Check the reading at several points

28. Radial Runout • Difference in radius from the center axis of rotation (out-of-round) • Maximum for a tire • 0.060" (1.5 mm) • Maximum for a wheel • 0.035" (0.9 mm)

29. Measuring Radial Runout • Mount a dial indicator with the stem against the tread and the lip of the rim • Check the reading at several points

30. Wheel Balance • Improper wheel balance is a common cause of tire and steering wheel vibration • When one side of a tire is heavier than the other, centrifugal force tries to throw the heavy side outward when the tire is rotating

31. Static Imbalance Caused by a heavy spot located in the center of the tire tread

32. Dynamic Imbalance The heavy spot is to one side of the tread or on the sidewall

33. Wheel Balancing • Wheels are balanced by adding wheel weights • Most weights are press-fit onto the wheel • Weights for some mag wheels stick onto the wheel with an adhesive backing

34. Wheel Balancing • Static balancing • add weights opposite the heavy area of the wheel • if a large amount is needed, add half to the inside and half to the outside of the wheel • Dynamic balancing • add weights exactly where needed • the dynamic balancing machine will indicate where weight must be added

35. Wheel Balancing

36. On-Car Balancing • Follow the equipment operating instructions • Wear eye protection • Remove rocks and debris from the tread • Place the vehicle on a jack stand • When using the engine to spin the drive wheels, do not exceed 35 mph(40 to 56 km/h) • when one wheel is on the floor, the free wheel will turn at twice the indicated speed

37. On-Car Balancing With a limited-slip differential, raise both rear wheels off the floor

38. Wheel Balancers • A wheel balancing machine is used to determine which part of a wheel assembly is heavy • Bubble balancer • static balance • Off-car balancer • static or dynamic balance • On-car balancer • static or dynamic balance

39. Bubble Balancer The wheel and tire assembly is mounted on the machine

40. Bubble Balancer Add weights until the bubble is centered

41. Off-Car Balancer • The wheel and tire assembly is mounted on the machine and rotated • The machine will indicate where weights should be added • After adding weights, spin the tire again to check for vibration

42. Off-Car Balancer

43. On-Car Balancer • Provides an electric motor to spin the wheel and tire assembly • An electronic pick-up unit or a hand-operated device is used to determine where weights are needed • Balances the wheel cover, brake disc, and lug nuts, along with the tire and wheel

44. Mounting and Dismounting Tires • A tire changing machine is used to force the tire on and off the wheel • prevents tire or rim damage • reduces the labor required

45. Tire Changing Machine Power head turns the bar to force the beads over the rim

46. Tire Changing Machine Applies tremendous force to stretch the tire bead on and off the wheel

47. Safe Work Practices • Wear eye protection • Keep your fingers out of the way • Never mount a tire on a rim that is not smooth and clean • Always lubricate the bead and wheel flange with the proper lubricant • Only inflate a tire on the machine or in a safety cage, as recommended

48. Safe Work Practices • Stand away from the tire when adding air; a loud “pop” sound will indicate when the beads seat • Do not exceed 40 psi (276–345 kPa) when initially inflating a tire • After inflation, install the core and inflate the tire to the recommended pressure

49. Finding/Repairing a Leak • Inflate the tire with air • Place the tire in a drum of water, or wet the tire with a water hose • Look for air bubbles forming on the tire or around the bead at the rim • Bubbles indicate leakage • Mark the leak with a crayon or chalk • Puncture must be in the tread to be repairable • There must be adequate tread left on the tire to be repairable • Punctures through the tread can be repaired with a plug if they are not too large, but punctures to the sidewall should not be repaired.

50. Wheel Bearing Service • Wheel bearings are normally filled with grease • Modern Vehicles usually do not have serviceable wheel bearings • If the grease dries out, the bearing will fail • Some bearings on older vehicles are serviceable • Most newer bearings are sealed units • Wheel bearings on front-wheel –drive vehicles are difficult to service and require special methods or tools.