English: The coordinate system used for a tire is described by Pacejka and Cossalter and has its origin at the intersection of three planes: the wheel midplane, the ground plane, and a vertical plane through the hub. The x-axis is in the ground plane and oriented forward, 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.