The figure illustrates the relation between the position of the instantaneous axis of rotation and wheelbase or track changes during suspension movement using the example of a plane semitrailing-arm wheel suspension.
→The points of intersection (penetration points) of the instantaneous axis of rotation through the planes of projection appear here in the respective views as instantaneous centers of rotation (L, Q).
→The position of the instantaneous axis of rotation not only determines the position of the wheel for small displacements, but also the transfer of forces between the tire contact centre and body.
→In case of plane and spherical suspensions, forces intersecting or parallel to the instantaneous axis of rotation do not produce a moment.
→In 3-D Suspensions however a torque is produces when the instantaneous pitch is not zero.