What Is Steering Axis Inclination on an Alignment

SAI is the measurement in degrees of the steering pivot line when viewed from the front of the vehicle. This angle, when added to the camber to form the included angle (see below) causes the vehicle to lift slightly when you turn the wheel away from a straight ahead position.

Why is the steering axis inclination of turn is necessary?

Steering axis inclination (SAI) causes both front wheels to gain positive camber as they steer away from center. This acts with caster to provide self-centering of the front wheels. This gives the car straight line stability.

What angle should front wheel alignment be?

The centre line should be 90 degrees from the rear axle, which in turn means there is 0 degree thrust angle. Any value other than 0 will affect the relationship between the front and rear wheels and cause “crabbing”, making the steering wheel pull either left or right.