Variable ratio rack and pinion systems eliminate the compromise that constant ratio systems have by allowing the designer to utilise a "best fit" approach for tuning the vehicle responses over a wide range of driving conditions
In high speed driving, increased lateral acceleration as a result of high downforce and higher normal loads acting on the tyres results in increased loads on the steering rack. By employing variable ratio, a reduction in steering torque can be achieved.
Variable ratio can also be used to tune the yaw gain or sensitivity of the vehicle to steering inputs. A high yaw gain makes the vehicle feel very nervous in high speed corners where the smallest steering wheel input results in what feels like an excessive response.
In electric power steering systems (pinion assist), variable ratio allows the designer to balance the power requirements of the system.