The suspension system of a vehicle consists of the shocks, springs and, if applicable, the torsion bars. As a vehicle travels on any type of roadway surface, it encounters bumps and dips in the roads, which are absorbed by the vehicle's suspension system. By absorbing the effects of a rough road, the suspension system allows the occupants of a vehicle to remain comfortable and in control of the vehicle. If not for the suspension system, the vehicle could be bounced out of control by the severe impact that encountering a bump in a rigid chassis would produce.
Some of the earliest vehicle designs did not incorporate a suspension system into the chassis. As such, the vehicles had an adverse reaction to the rough roads of the period. Occupants of these harsh riding automobiles suffered from bumps and bruises as they were tossed about the confines of the vehicle. The vehicles themselves were victims of the rough ride as parts were damaged due to the impact and lack of give designed into the chassis.
As the automobile evolved worldwide, the leaf spring suspension system was the first attempt at controlling the unfriendly ride associated with automobile travel. While the addition of the leaf spring proved to absorb some of the harsh ride characteristics, the vehicles reacted more like bouncing toys than adult transportation. When a vehicle encountered a severe bump, the leaf springs absorbed the initial impact of the bump; however, the springs continued to allow the weight of the vehicle to compress them, and an uncontrollable bounce ensued.
In an effort to control the bouncing reaction to bumps, the shock absorber was added to the suspension system. The shock absorbers were not the advanced marvels of today. The shocks were actually friction shocks and were comprised of leather disks sandwiched between two metal arms. As the arms moved with the suspension, the leather disk provided friction, which halted the vehicle's motion, thereby controlling the bounce.
Leaf springs gave way to coil springs and torsion bars as the evolution of the suspension system developed into the system used today. Advances in shock-absorber technology have advanced to the point that the shock absorber is one of the most critical components of the modern suspension system and not just an afterthought. Many vehicles now offer options such as automatic shock dampening, which allows a vehicle's on-board computer system to adjust the ride quality of the vehicle for the most comfortable ride possible.