<div class="htmlview paragraph">Currently all or most suspensions and their motions are assumed to be planar, and are kinematically modeled as two dimensional mechanisms. Therefore the instant rotation centers, including the instant rotation center of the vehicle body with respect to the ground (commonly known as the “roll center”) and the instant rotation center of a suspension with respect to the vehicle body, are all on the same plane.</div> <div class="htmlview paragraph">In this paper all suspensions will be assumed truly spatial or three-dimensional, and then the instant screw axis theory and the associated computational and kinematical methods will be developed to replace all the instant rotation centers and roll axes by the instant screw axes, for a much accurate three-dimensional kinematic analysis.</div> <div class="htmlview paragraph">To present the theory and methods in more detail, the three major suspensions, namely, Double-Wishbone, McPherson, and Multilink suspensions, are used as illustrated examples with numerical data, equation derivations, and computational results.</div>