1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 74
Wheel Alignment

3. Contents Wheel alignment principles Caster Camber Toe
Steering axis inclination
Setback
Toe-out on turns (turning radius)
(Continued)

4. Contents Tracking Prealignment inspection Adjusting wheel alignment
Wheel alignment tools and equipment
Alignment machines
Road test after alignment

5. Wheel Alignment Principles
The main purpose of wheel alignment is to make sure the tires roll without scuffing, slipping, or dragging under all operating conditions

6. Alignment Angles
Six fundamental angles are needed for proper wheel alignment:
caster
camber
toe
steering axis inclination
toe-out on turns (turning radius)
tracking (thrust line)

7. Caster
Forward or rearward tilt of the steering axis (steering knuckle) when viewed from the side of the vehicle
Controls the tire’s load distribution in relation to an imaginary centerline drawn through the spindle support
Caster does not affect tire wear

8. A shopping cart caster wheel illustrates negative caster

9. A bicycle wheel represents positive caster

10. Purposes of Caster Aid directional control
Cause the wheels to return to the straight-ahead position
Offset road crown pull (steering wheel pull caused by the hump in the center of the road)

11. Positive Caster
Tilts the top of the steering knuckle toward the rear of the vehicle
Helps keep the wheels traveling in a straight line
When the wheels are turned, it lifts the vehicle
The vehicle’s weight tends to push the wheels back to the straight-ahead position

12. More common on vehicles with power steering
Positive Caster
More common on vehicles with power steering

13. Negative Caster
Tilts the top of the steering knuckle toward the front of the vehicle
The wheels will be easier to turn
The wheels will tend to swivel and follow imperfections in the road

14. May be used on vehicles with manual steering, to ease steering effort
Negative Caster
May be used on vehicles with manual steering, to ease steering effort

15. Measured in degrees, from true vertical
Caster Measurement
Measured in degrees, from true vertical

16. Caster and Road Crown Effect
Road crown is the normal slope toward the outer edge of the road surface

17. Caster and Road Crown Effect
Road crown causes the weight of the vehicle to pull the vehicle away from the center of the road
Caster is commonly used to offset the effect of road crown
The right front wheel may be set with slightly more positive caster than the left
the vehicle pulls toward the side with the more negative caster

18. Camber
Inward or outward tilt of the wheel and tire assembly when viewed from the front of the vehicle
Controls whether the tire tread touches the road surface evenly
Affects tire wear

19. Purposes of Camber To prevent tire wear on the outer or inner tread
To load the larger inner wheel bearing
To aid steering by placing the vehicle’s weight on the inner end of the spindle

20. Positive and Negative Camber
Positive camber
the tops of the wheels tilt outward when viewed from the front
most manufacturers specify a positive setting of about 1/4º to 1/2º
Negative camber
the tops of the wheels tilt inward when viewed from the front

21. Positive and Negative Camber

22. Measured in degrees, from true vertical
Camber Measurement
Measured in degrees, from true vertical

23. Toe
Difference in distance between the front and rear of the left- and right-hand wheels
Measured in inches or millimeters
Controls whether the wheels roll in the direction of travel
Affects tire wear

24. Toe Toe-in: wheels are closer at the front than at the rear
Toe-out: wheels are farther apart at the front than at the rear

25. Rear-Wheel-Drive Toe Settings
Rolling resistance and steering system play tend to cause toe-out when driving
Toe-in compensates for these factors
By adjusting the front wheels for a slight toe-in, the wheels and tires roll straight ahead when driving
Typical setting:
1/16"–1/4" (1.6 mm–6 mm)

26. Front-Wheel-Drive Toe Settings
The front wheels are pushed forward by engine torque, causing the wheels and tires to toe in
To compensate for this action, front-wheel-drive vehicles normally have the front wheels adjusted for a slight toe-out
Typical setting:
1/16" (1.6 mm)

27. Steering Axis Inclination
The angle, away from the vertical, formed by the inward tilt of the steering axis (ball joints, king pin, or MacPherson strut tube)
Aids directional stability by helping the steering wheel return to the straight-ahead position
Does not affect tire wear

28. Steering Axis Inclination
If the angle is incorrect, part replacement is needed

29. Setback
One front wheel is set farther back from the front of the vehicle than the other front wheel
with positive setback, the right wheel is farther back than the left wheel
with negative setback, the left wheel is farther back than the right wheel
Excessive setback will cause pull

30. Setback
Manufacturing tolerances generally allow a small amount of setback
Excessive setback is usually the result of collision damage

31. Toe-Out on Turns (Turning Radius)
Amount the front wheels toe-out when turning corners
As the vehicle corners, the inside tire must travel in a smaller radius circle than the outside tire
The inside wheel turns sharper than the outside wheel

32. Toe-Out on Turns

33. Toe-Out on Turns
Eliminates tire scrubbing and squealing by keeping the tires rolling in the right direction during turns
Not an adjustable angle
If the angle is incorrect, it indicates bent or damaged steering parts

34. Tracking
Position or direction of the two front wheels in relation to the two rear wheels
With the proper tracking, the rear tires follow in the tracks of the front tires
With improper tracking, the rear tires do not follow the tracks of the front tires
increased tire wear, lower fuel economy, and handling problems can result

35. Tracking

36. Prealignment Inspection
Before attempting wheel alignment, make sure all steering-related and suspension-related parts are in good condition
It is impossible to properly align the wheels on a vehicle with worn or damaged parts

37. Prealignment Inspection Points
Check for the following:
loose wheel bearings
wheel or tire runout
worn tires
tires of different sizes and types
incorrect tire inflation
worn steering or suspension components
incorrect curb height and weight
incorrect cradle alignment

38. Reading Tire Wear

39. Cradle Alignment
The cradle is the strong metal structure bolted to the frame rails on the body
holds the lower control arms, steering rack, and engine in alignment in the body
Loosening and moving the cradle can alter alignment
Alignment holes may be provided in the cradle and body to assure proper alignment

40. Adjusting Wheel Alignment
Caster, camber, and toe are the three commonly adjustable wheel alignment angles

41. Caster and Camber Adjustment

42. Caster and Camber Adjustment

43. Changing the tie-rod length on a rack-and-pinion unit
Toe Adjustment
Changing the tie-rod length on a rack-and-pinion unit

44. Changing the tie-rod length on a linkage-type steering system
Toe Adjustment
Changing the tie-rod length on a linkage-type steering system

45. Centering Steering Wheel

46. Adjusting Rear Wheel Alignment
Some vehicles have provisions for rear wheel alignment
Rear wheel alignment problems can occur due to component wear or damage
Procedures for rear wheel adjustment vary

47. Adjusting Rear Wheel Alignment
On this axle, shim placement changes alignment angles

48. Wheel Alignment Tools and Equipment
Various equipment and special tools are needed
The most basic equipment includes the turning radius gauge, the caster-camber gauge, and the tram gauge
Alignment racks integrate the functions of all these gauges into one machine

49. Wheel Alignment Tools

50. Wheel Alignment Tools
A. Steering wheel lock
B. Brake pedal depressor

51. Turning Radius Gauges
Measure how many degrees the front wheels are turned right or left
Commonly used when measuring caster, camber, and toe-out on turns
The gauges may be portable or mounted on the alignment rack

52. Using Turning Radius Gauges
Center the front wheels of the vehicle on the turning radius gauges
Pull out the locking pins so the gauge and tire turn together
The pointer on the gauge will indicate how many degrees the wheels have been turned

53. Checking Toe-Out on Turns
Center the front wheels of the vehicle on the turning radius gauges
Turn one of the front wheels until the gauge reads 20º
Read the number of degrees showing on the other gauge
Check both the right and left sides
both sides must be within specs

54. Caster-Camber Gauges
Used with the turning radius gauge to measure caster and camber in degrees
Secured on the wheel hub magnetically or fastened on the wheel rim
Caster and camber are adjusted together since one adjustment may affect the other

55. Caster-Camber Gauge Mounting

56. Tram Gauges
Used to compare the distance between the front and rear of a vehicle’s tires for checking toe adjustment

57. Alignment Machines
The alignment machine consists of a rack, console, and related parts
Rack
consists of a lift, turning radius gauges, and equipment for measuring alignment angles
Console
consists of a color monitor, keypad, and computer

58. Alignment Machine

59. Console
This console provides training, instructions, specifications, and feedback when doing wheel alignment

60. Software
Alignment equipment software contains computer instructions, equipment operating instructions, and alignment specifications
When installed in the computer, the software will help you adjust all alignment angles quickly and easily
Usually stored on a CD-ROM

61. Alignment Heads Mount on the vehicle’s wheels
Brackets are used for mounting the alignment heads on the wheels
Use lasers or proximity sensors to compare the alignment of each wheel
Used to check caster, camber, and toe

62. Alignment Head

63. Using Alignment Equipment
Always follow the operating instructions provided by the manufacturer
Drive the vehicle up on the lift
Carefully center the front tires on the turning radius gauges
Block the rear wheels
Mount the alignment heads on the wheels

64. Using Alignment Equipment
Turn on the alignment console
Follow the computer prompts
After you identify the vehicle, the computer will retrieve stored data about performing an alignment on the vehicle
As you make adjustments, the equipment will monitor the changes in the alignment angles

65. Using Alignment Equipment
This technician is using a four-wheel alignment machine with a color monitor

66. Using Alignment Equipment
This monitor is displaying alignment angles with instructions for adjustment

67. Road Test after Alignment
Always road test the vehicle to check your work
Drive on level pavement
Check the steering wheel alignment
Feel for steering wheel pull
Check for other problems, such as noise or vibration

68. Noise and Vibration Diagnosis Chart