Suspension has been an essential component of automobiles as long as they have been in production. The rear suspension of a vehicle performs the same general function as front suspension, but the specific construction is typically quite different. The ideal suspension for a vehicle depends a lot on the vehicle's body style and performance requirements.
The most basic purposes of a suspension system are to prevent the body of a vehicle from hitting the ground and to keep the tires in contact with the road.
Suspension is mechanically more complex for a pair of wheels that receives power from the engine. The suspension must be able to handle the transfer of engine torque effectively to the wheels while resisting the rotational force of the driveshaft. In vehicles that have rear-wheel drive, the rear suspension usually has more components than the front suspension.
The suspension for the first automobiles was similar to those used in horse-drawn carriages. These early suspension systems quickly proved inadequate for the greater speeds that were possible with vehicles powered by internal-combustion engines. One of the first major refinements in the suspension of these vehicles was self-damping shock absorbers that dissipated the forces caused by the irregularities in road surfaces.
Modern vehicles have a rear suspension system composed of several varying components, including linkages, shock absorbers and springs. These components must perform distinct functions that often require the rear suspension to have different properties. A car's suspension system is therefore a compromise between conflicting requirements.
The suspension of a vehicle directly affects characteristics such as passenger comfort and handling. The rear suspension of a luxury coupe is designed to maximize comfort and will have a softer suspension that absorbs more movement. A rear-drive sports car will require a stiffer suspension that allows power to be transferred from the drive shaft to the rear wheels more efficiently.
Suspension systems are generally classified into dependent and independent systems. The wheels in a dependent system are perpendicular to the axle and parallel with each other. The most common suspension of this type is leaf-spring rear suspension, which consists of multiple metal bars, or leaves, bound together. It is an older design but is still most common on trucks and other heavy vehicles.
An independent suspension system allows the wheels on the same axle to move vertically without affecting the other wheel. A very common type of independent suspension for the rear wheels of passenger vehicles is the "double wishbone" suspension. This type of rear suspension uses a pair of arms shaped like wishbones. The primary advantage of a double wishbone suspension is that it's easily adjustable to provide the desired riding characteristics.
The rear suspension has a profound effect on a vehicle's behavior, especially while cornering or traveling over bumpy roads. Many specific types of suspension are currently available, so automobile engineers must carefully choose the best suspension for each vehicle.