[Gary Dillard]

To understand this concept, draw a top view of your robot and consider how it turns about the center. The 2 middle wheels move tangent to the circle in their direction of rotation, while the 4 outboard wheels move at an angle so they tend to drag sideways (and you'll see robots "jumping" as they turn to overcome this). The idea is to let the center wheels hold most of the weight while turning, so along with this you want to try to have your center of mass as close to the center of the robot (that hole) as possible.