Kingpin inclination (KPI) measures the angle formed between true vertical and the line drawn through the upper and lower steering pivot points. This inward tilt forces the vehicle chassis to lift slightly when the wheels are turned away from straight ahead. The vehicle's weight then naturally pushes the wheels back to the center, providing steering stability and self-centering effort.
The alignment rack shows the KPI is out by two degrees on the left, which means that strut housing is probably bent.
Also heard as
- steering axis inclination
- SAI
Do not mix it up with
- Camber: Camber is the tilt of the wheel itself, whereas KPI is the tilt of the unseen steering pivot axis.
Related terms
Kingpin
The main pivot axis or physical pin around which a steered wheel turns.
Camber
The inward or outward tilt of a vehicle's wheels when viewed from the front or rear.
Camber angle
The specific measurement in degrees of a wheel's vertical tilt relative to the road surface.
Caster
The forward or backward tilt of the steering axis when viewed from the side of the vehicle.