public float suspensionDistance { get; set; }

Suspension always extends downwards the local y-axis. Suspension travel will be scaled by the transform's scale. The value suspensionDistance is the distance that the wheel travels as it moves along the local up vector of the rigid body from the coordinate of the wheel center at maximum spring elongation to the coordinateof the wheel center at maximum spring compression. It is expressed in metres. The range of suspension travel will be scaled by the transform's scale.