Castor_Camber_Kingpin.pdfVIP

Front Wheel Geometry (Castor, Camber and King Pin Inclination) INTRODUCTION The steering and road holding of a car depend to some extent on the layout and orientation of the stub axles on which the front wheels are mounted. The suspension geometry is defined by the traditional terms camber angle, toe-in, and the swivel angles called castor and king pin inclination. These are shown in the following diagram, which also shows how they are inter-related. Caster, Camber and Kingpin Experiment 1 Toe-in is the very small angle between the front wheel plane and the longitudinal axis of the car. It can be measured as the difference in the distance between the near side and offside wheel rims at the front and rear of the wheels. The object of toe-in is the keep the steering linkages under tension when driving straight ahead. The camber angle is the angle, as viewed from the front of the car, between the plane of the front wheels and a vertical plane, and is called positive when the top of the wheels leans outward from the body of the car. A slight positive camber reduces the cornering power at the front and normally results in an understeering car. King pin inclination is the transverse angle of the swivel axis of the front wheel and its stub axle. The effect of the inclination is usually discussed in terms of the king pin offset which determines the self centering torque when the steering is turned for cornering. Although many cars have a positive value of offset which tends to return the wheel to the straight ahead position, some modern cars have a negative offset to improve stability when the tire blows or the brake fails on one front wheel. Castor angle also introduces a self-centering torque when the car is traveling forward. This is achieved by the positive offset shown in the diagram where the contact of the tire on the road trails behind the king pin axis. With modern car design it has become more difficult to see and comprehend the int