'Deflected' tread path, sideslip velocity and slip angleGraph of cornering force vs slip angleA coordinate system used for tire analysis by Pacejka and Cossalter. The origin is at the intersection of three planes: the wheel midplane, the ground plane, and a vertical plane aligned with the axle (not pictured). The x-axis is in the ground plane and the midplane and is oriented forward, approximately in the direction of travel; the y-axis is also in the ground plane and rotated 90º clockwise from the x-axis when viewed from above; and the z-axis is normal to the ground plane and downward from the origin. Slip angle and camber angle are also shown.
In vehicle dynamics, slip angle[1] or sideslip angle[2] is the angle between the direction in which a wheel is pointing and the direction in which it is actually traveling (i.e., the angle between the forward velocity vector and the vector sum of wheel forward velocity and lateral velocity , as defined in the image to the right).[1][3] This slip angle results in a force, the cornering force, which is in the plane of the contact patch and perpendicular to the intersection of the contact patch and the midplane of the wheel.[1] This cornering force increases approximately linearly for the first few degrees of slip angle, then increases non-linearly to a maximum before beginning to decrease.[1]
The slip angle, is defined as
^ abcdPacejka, Hans B. (2006). Tire and Vehicle Dynamics (Second ed.). Society of Automotive Engineers. pp. 3, 612. ISBN0-7680-1702-5.