King Pin Inclination| Steering Axis Inclination

King Pin Inclination (KPI) is a critical suspension geometry parameter that significantly influences a vehicle's handling and steering characteristics. It's particularly important in front-wheel-drive vehicles.
What is KPI?
Definition: KPI is the angle between the steering axis (the imaginary line passing through the upper and lower ball joints of the suspension) and the vertical, when viewed from the front of the vehicle.
Positive KPI: The top of the steering axis leans towards the center of the vehicle.
Negative KPI: The top of the steering axis leans away from the center of the vehicle.
Why is KPI Important?
Steering Return: Positive KPI helps the wheels return to the straight-ahead position after a turn, improving steering stability.
Caster Effect: KPI contributes to the caster effect, which further aids in steering return and directional stability.
Scrub Radius: KPI influences the scrub radius, which is the distance between the tire contact patch and the point where the steering axis intersects the ground. A smaller scrub radius generally improves steering feel and reduces torque steer.
Camber Changes: KPI affects how camber changes as the suspension moves up and down, influencing tire contact and grip during cornering.
Visualizing KPI:
Typical KPI Values:
Most modern vehicles have positive KPI values ranging from 5 to 10 degrees.
The specific value depends on various factors, including vehicle type, suspension design, and desired handling characteristics.
In Summary:
King Pin Inclination is a fundamental suspension geometry parameter that plays a crucial role in vehicle handling and steering. By carefully adjusting KPI, engineers can fine-tune a vehicle's behavior to achieve optimal performance and driver comfort.