Pitch angle of kingpin: the angle at which the kingpin axis inclines inward relative to the wheel centerline. The role of the kingpin inclination angle is to make the wheel automatically return to the correct position in time after steering, so as to steer easily.
Because the kingpin inclines inward, the steering wheel rotates around the kingpin during steering, and the wheels must be trapped below the ground. Of course, this is impossible. When actually turning, the front of the car was forced to rise slightly. In this way, the gravity of the car will automatically reset the steering wheel.