1. Wheel Alignment
CASTER

4. Effects of Caster
High Positive Caster increases ( + )
Straight ahead stability
Steering effort required is high
Steering wheel return to center
Road Shock felt from bumps
More Negative Caster ( -- )
No Straight ahead stability
Steering effort is light
Wheel not returning to center
Smooth ride, little road shock
Uneven Caster will cause the vehicle to pull towards the side with less Caster (more Negative -)
½ degree or more
Not a tire wearing angle!!!!

5. Caster can be set unevenly to counter act for road crown pull.
Usually ½ degree or more on the downhill side.
Caster trail is the distance between the caster line and the tire point of contact.

6. CAMBER

7. Camber = The inward or out ward tilt of the centerline of the tire.

8. Camber
The more camber you have, the more the load is placed on the outside of the tire.
Excessive positive or negative camber can cause tire wear on the edges

9. Camber can cause a car to pull to one side

10. Effects of Camber Tire wearing angle Directional control angle
Pull towards the side with more positive camber
Excessive Camber Accelerates bearing wear
Load is not evenly set on bearings.
Positive wears the inner bearing
Negative wears the outer bearing

11. Influences on Camber Uneven Loading Body roll during turns Road Crown
Rough road Surfaces
Suspension Wear
Suspension Damage
Tire size
Caster
Faster cornering wears out edges of tires!!!!

12. Camber can be set unevenly to counter act for road crown pull.
Cross Camber should never exceed ½ degree
Camber will pull to the most positive side
Camber Roll
Caster angle may produce a change in the camber angle when the wheels are turned

13. Camber is adjustable on most vehicles

16. Toe
Toe in Toe out

19. Darting
Darting

20. Wander

21. Toe
Toe in = Darting
Toe out = Wander

22. Effects of Toe
Tire wear
Scuffing sideways
Scuffing is Drag and hop!
Wear tends to be the same on both tires, unlike Camber wear
Directional control angle
Can cause shimmy!
Diagonal Wipe on the rear tires if toe is excessive
Lots of rotations!
Toe Change can occur as suspension travels up and down.
Measure toe change at 1 inch increments
Should be no change!
Check length and height of tie rods!!!
City driving can cause unusual tire wear that might be blamed on Toe problems!!

23. Steering Axis Inclination
SAI
Steering Axis Inclination

24. (looking from the front)
SAI
The inward tilt at the top of the strut.
(looking from the front)

25. (looking from the front)
SAI
The inward tilt at the top of the strut.
(looking from the front)

26. SAI and Included angle
Include angle =
SAI + pos. camber

29. Effects of SAI Ensures Steering stability
FWD use more SAI because of small Caster
Helps with Steering Wheel returnability
Uses Gravity to assist

30. Diagnosis with SAI SLA & Strut/SLA
Camber
Included Angle
Diagnosis
Correct
< spec
Bent steering Knuckle
< Spec
> Spec
Bent lower control arm
Bent lower arm & Knuckle or spindle
Bent upper control arm

31. Diagnosis with SAI Strut Suspensions
Camber IA
Diagnosis
Correct
< spec
Bent spindle or strut
> Spec
Bent control arm or strut
>Spec
Bent control arm or strut or spindle.
strut tower out at top
strut tower in at top
correct
Strut tower in at top
And bent spindle & strut

32. 0 bump steer Zero SAI would = Major bump steer No toe angle change.
Need to Check for this at 1 inch increments
3 factors affect bump steer
Tie rod length
Relative heights of inner and outer tie rod ends
Steering arm length
Zero SAI would = Major bump steer

33. Positive Scrub Radius Positive scrub radius RWD vehicles Sport cars
Feel the steering wheel tug when braking
Road feel
Driver Involvement needed

34. Negative Scrub radius Used on Split diagonal braking systems
Self Correcting when braking
No driver involvement needed
No road feel

36. Effects of:
Larger tire
smaller tire
deep dish
wheel
Larger Scrub = harder to turn and increased wear
Smaller Scrub = easy turns
Braking stability - Negative has greater directional stability
Positive decreases braking stability (aftermarket rims)

37. Turning Angle
Setback
Thrust Angle.

38. Turning Angle

39. Setback

40. Thrust

41. The End
Thanks to Specialty Products Company