While changing the handling characteristics of a conventional vehicle normally requires physical modification, a vehicle equipped with steer-by-wire can accomplish the same effect through active steering intervention. This paper presents an intuitive method for altering a vehicle's handling characteristics by augmenting the driver's steering command with full vehicle state feedback. The vehicle can be made more or less responsive depending on the driver's preference and particular operating conditions. Achieving a smooth, continuous change in handling quality requires both accurate state estimation and well-controlled steering inputs from the steer-by-wire system. Accurate estimates of vehicle states are available from a combination of global positioning system (GPS) and inertial navigation system (INS) sensor measurements. By canceling the effects of steering system dynamics and tire disturbance forces, the steer-by-wire system is able to track commanded steer angle with minimal error. Experimental results verify that with precise steering control and accurate state information, the handling modification is exactly equivalent to changing the front tire cornering stiffness.