Two-wheeled vehicles such as a bicycles and motorcycles are commonly constructed with a single unibody type frame which extends from or between a front wheel and a rear wheel, with a front component of the frame or fork to which the front wheel is attached being attached to the main body of the frame by a pivot to allow the front wheel to be turned about the pivot relative to the frame. The front fork pivot is defined by a cylindrical receiver located at a forward end of the frame and oriented at a forward angle, and a fork post which fits and rotates within the receiver.
The rear section of the frame is typically of a fixed configuration so that the rear wheel generally follows the track of the front wheel, as shown for example in FIG. 8B, FIG. 9B and FIG. 11. As well known in the mechanics and physics of two-wheeled vehicles, with the rear wheel permanently aligned with the frame turning requires leaning of the frame in the direction of the desired turn. At speed, the required directional leaning is induced by counter-steering the front wheel, which is a momentary turning of the front wheel in a direction opposite to the desired turn direction. Once the lean of the frame is initiated in this manner the front wheel is then pivoted back to center and further in the direction of the turn and defines the outer radius of the turn path, as shown in FIGS. 8B and 9B.