1. Tire, Wheel, and
Wheel Bearing
Fundamentals

2. Contents Tires Wheels Valve stems and cores Lug nuts, studs, and bolts
Wheel weights
Hub and wheel bearing assemblies

3. Tires Tires perform two basic functions:
act as a soft cushion between the road and the metal wheel
provide adequate traction (friction) with the road surface

4. Tire Types Pneumatic Tubeless tire Tube-type tire filled with air
internal air pressure pushes out on the inside of the tire to support the vehicle
Tubeless tire
does not use an inner tube
tire and wheel form an airtight unit
Tube-type tire
uses an inner tube to hold air pressure

5. Tubeless Tire

6. Parts of a Tire

7. Tire Rolling Resistance
Measurement of the amount of friction produced as the tire operates on the road surface
High rolling resistance increases fuel consumption and wear
Rolling resistance is reduced by higher inflation pressure, tire design, and a lighter vehicle

8. Tire Construction There are many design variations:
different numbers of plies may be used
plies may run at different angles
different materials may be used
Three types of tires used on automobiles:
bias ply
belted bias tire
radial tire

9. Bias Ply Tire Plies run on an angle from bead to bead
Angle is reversed from ply to ply
Does not use belts
Body of the tire flexes easily
Provides a smooth ride
Plies and tread are weakest
reduces traction at high speeds
increases rolling resistance

10. Bias Ply Tire

11. Belted Bias Tire
Bias tire with belts added to increase tread stiffness
Belts lie under the tread area only
Two stabilizer belts and two or more plies improve tire performance
provides a smooth ride and good traction
reduces rolling resistance

12. Belted Bias Tire

13. Radial Ply Tire Plies run straight across from bead to bead
Stabilizer belts lie beneath the tread
Belts can be made of steel, flexten, fiberglass, or other materials

14. Radial Ply Tire Uses a very flexible sidewall with a stiff tread
provides a very stiff footprint
improves safety, cornering, braking, and wear
may produce a harsher ride at low speeds

15. Radial Ply Tire

16. Tire Sidewall Markings

17. Tire Size
Alpha-Numeric–Uses letters and numbers to denote tire size in inches and its load- carrying capacity in pounds

18. P-Metric–Uses metric values and international standards
Tire Size
P-Metric–Uses metric values and international standards

19. Points of Measurement

20. Aspect Ratio
Height-to-width ratio of a tire. Comparison of a tire’s height and width

21. Maximum Load Rating
Amount of weight the tire can carry at the recommended inflation pressure
Printed on the sidewall
P-metric:
given in kilograms and pounds
Alpha-numeric:
indicated by a letter such as B, C, or D

22. Maximum Inflation Pressure
Highest air pressure that should be pumped into the tire
Many tires have a maximum recommended pressure of 32 to 40 psi (220 to 275 kPa)

23. Tread Plies Number of plies and ply rating:
2-ply with a 4-ply rating
4-ply
Greater number of plies usually indicates a greater load-carrying capacity

24. DOT Serial Number
Identifies the manufacturer, plant, location, construction, and date of manufacture
Stamped into the sidewall
Department of Transportation rating means the tire has passed prescribed safety tests

25. Tire Grades Tread wear Tire traction Tire temperature resistance
given as a number, 100 to 500
higher number is more resistant to wear
Tire traction
given as an A, B, or C
“A” rating has the most traction
Tire temperature resistance
“A” rating resists temperature buildup best

26. Speed Rating
Maximum allowable sustained road speed a tire can safely withstand without failure
Ratings range from B to Z
“B” rating 31mph or 50 km/h
“Z” rating 149 mph or 238 km/h

27. Wear Bars
When too much tread has worn away, solid rubber bars will show up across the tread

28. This is a high pressure spare, requiring 60 psi (415 kPa)
Compact Spare Tire
This is a high pressure spare, requiring 60 psi (415 kPa)

29. Self-Sealing Tires Coating of sealing compound is applied to the liner
If a nail punctures the tire, air pressure will push the soft compound into the hole to stop air leakage

30. Self-Sealing Tire Action
A. Nail punctures tire B. Nail is pulled out C. Sealing compound flows into the hole

31. Retreads
Used tires that have had a new tread vulcanized to the old carcass, or body
Large truck tires are often recapped because of the high cost of new truck tires

32. Run-Flat Tires Use extremely stiff sidewall construction
Still usable with a loss of air pressure
Tire will still retain most of its shape because the sidewall is strong enough to support vehicle weight

33. Run-Flat Tires

34. Tire Inflation Monitoring System
Often used with run-flat tires
Pressure sensors are mounted on each wheel
If tire pressure is not correct, the wheel sensor produces a radio signal
Signal is received by a module that turns on a dash warning light

35. Pressure Sensor

36. System Operation

37. Wheels
Designed to support the tire while withstanding loads from acceleration, braking, and cornering
Made of steel, aluminum, or magnesium
Lightest weight is desirable to reduce “unsprung” weight, improving handling

38. Wheel Assembly

39. Aluminum or magnesium wheels are often called “mags”
Mag Wheels
Aluminum or magnesium wheels are often called “mags”

40. Drop-Center Wheel
Allows for easier installation and removal of the tire
Center of the wheel is smaller in diameter than the rim
When installing a tire, it can fall into the recess, then, the other side of the tire bead can be forced over the rim

41. Note the smaller diameter in the center of the rim
Drop-Center Wheel
Note the smaller diameter in the center of the rim

42. Dimensions of a Wheel

43. Safety Rims
Small ridges on the rim hold the tire on the wheel during a tire blowout or flat

44. Valve Stems and Cores Valve stem Valve core Valve cap
pressed into a hole in the wheel of a tubeless tire to allow inflation and deflation
Valve core
spring-loaded air valve that is threaded into the valve stem
Valve cap
protects the air valve and stem threads from dirt, moisture, and damage

45. Valve Stem Assembly Valve stem snaps into the hole in the wheel
Press fit forms an airtight seal
Valve core screws into the valve stem body

46. Lug Nuts, Studs, and Bolts
hold the wheel and tire assembly on the vehicle
Lug studs
special studs that accept the lug nuts
Lug bolts
used instead of nuts
screw into threaded holes in the hub or axle flange

47. Lug Nut and Stud Stud is pressed into the hub or axle flange
If metric or left-hand threads are used, markings will normally be given

48. Wheel Weights Small lead weights
Attached to the wheel rim to balance the wheel-and-tire assembly
Used to offset a heavy area of the wheel and tire

49. Hub and Wheel Bearing Assemblies
Allow the wheel to turn freely around the spindle, in the steering knuckle, or in the bearing support
Most wheel bearings are tapered roller bearings or ball bearing

50. Tapered Roller Bearing
Lubricated with high-temperature grease

51. Balls allow parts to rotate with a minimum amount of friction and wear
Ball Bearing
Balls allow parts to rotate with a minimum amount of friction and wear

52. Hub and Wheel Bearing (Nondriving Wheels)
Spindle is stationary, providing a mounting place for the wheel bearings, hub, and wheel
Hub is partially filled with grease to lubricate the bearings
Nut on the end of the spindle allows adjustment of the bearing preload

53. Hub and Wheel Bearing (Nondriving Wheels)

54. Hub and Wheel Bearing (Nondriving Wheels)
Used on the front of rear-wheel-drive cars or the rear of front-wheel-drive cars

55. Hub and Wheel Bearing (Driving Wheels)
Axle shaft rotates inside a stationary support
Drive shaft fits through the center of the bearings
Hub is splined to the axle shaft
Ball bearings are lubricated by thick, high- temperature grease

56. Hub and Wheel Bearing (Driving Wheels)

57. Hub and Wheel Bearing (Driving Wheels)
Commonly used on the front of front-wheel- drive vehicles

58. Hub and Wheel Bearing (Four-Wheel Drive)
Front drive axle extends through a stationary spindle
Special free-wheel, or locking hub transfers power from the axle to the hub- disc assembly when in four-wheel-drive

59. Hub and Wheel Bearing (Four-Wheel Drive)
Front axle, brakes, hub, and wheel bearing assembly