IC come from the study of kinematics in two dimensions (in a plane ).They are a convenient graphic aid in establishing motion relationships between two bodies. In ช่วงล่าง design it is convenient to break down this three-dimensional problem in two, two-dimensional problem. We talk about the front view and the side view geometry. What we are doing is cutting vertical plane(90 to the ground) though to the vehicle center line. We than project all the ช่วงล่าง point onto these planes