1. Alignment Fundamentals, Part Two

2. Steering Axis Inclination (SAI)
The inward tilt at the top of the strut.
(looking from the front)

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

4. Zero SAI would = Major bump steer
SAI and Bump steer
Zero SAI would =
Major bump steer

5. 0 Bump Steer SAI line meets tire vertical CL at road surface
Tire wear reduced
Steering effort decreased
Less stress on components

6. SAI Safety Factors Unequal causes serious handling problems
Torque steer
Pulling during braking
Bump steer
If SAI is out of spec
Camber will be out of spec
Bent or damaged components

7. Scrub Radius
Distance between SAI line & True Vertical CL of tire at road
Positive scrub radius – SAI line meets road inside CL of tire
Negative Scrub Radius – SAI line meets road outside CL of tire

8. Pos. Scrub Radius

9. Negative Scrub Radius
Commonly used on front wheel drive vehicles

10. Toe
The distance between the inside front edges and the inside rear edges of the tires
Wears tires with a feathered edge
Toe-out-on-turns – inside wheel at sharper angle that outside

11. Toe In & Out

12. Turning Radius & Toe-Out-On-Turns