Independent front suspension was developed in the 1930s to improve automobile performance by allowing each wheel to respond independently to bumps, ruts and road surface inconsistencies, rather than mounting a chassis on rigid axles. Rigid, or solid beam axles, work well for large vehicles at lower speeds, when responsive handling is not a primary concern, but smaller, faster cars built for performance or passenger use required a more flexible suspension. Independent front suspension has advantages over fixed suspension when it comes to handling and passenger comfort.
Improved Steering, Handling and Braking
In a rigid suspension, if one wheel jogs or bounces, the entire axle tilts, causing the opposing wheel to tip in or out at the top, no longer rolling straight ahead, an effect called "bump steer". Rigid axles are also less responsive on turns and vehicles carrying heavy loads are subject to instability called "shimmy", caused by forces translated across the axle from wheel to wheel. During hard braking, solid beam suspension can cause the front of the vehicle to nose dive and twist. Independent front suspension (IFS) corrects or vastly improves all of these effects by allowing wheels on the same axle to respond independently to driving conditions.
Ride quality is a concern that has evolved with our culture's increasing dependency on automobiles for recreational and commuter travel. Overall ride quality, or how comfortable a car feels to ride in or drive, is measured by a combination of factors, including noise and vibration, the translation of bumpy road surface to passengers, the smoothness of the car's steering and how well a car handles and corners. Independent front suspension solves some of these problems by decoupling the front wheels, improving overall stability and creating isolation between the suspension and the vehicle chassis.
Size and Fuel Efficiency
It is difficult to beat a solid axle for strength and simplicity, but the price of that strength is size and mass. For heavy duty vehicles and the solid steel cruisers of the 1940s and 1950s, a rigid axle made good design sense. As passenger vehicles have got smaller and more performance-oriented, heavy, bulky, rigid axles are no longer practical, particularly because heavier vehicles burn more fuel. Independent front suspensions have evolved with modern car materials, creating lighter, more flexible and responsive vehicles.