Over the years, technology has developed many innovative and interesting ways to suspend a truck. In the beginning, the truck had inherited its suspension from the buckboard wagon and stagecoach, using straight axles at both the front and rear, which were both suspended by leaf springs. The number of stacked leaves would determine the leaf spring pack's strength. This type of suspension proved to be rigid and firm, with not much softening or absorption of the terrain or surface imperfections, making for an uncomfortable and sometimes violent ride.
The objective of any suspension system is to reduce and control the energy of the up and down motion conducted by a vehicle's acceleration, braking, and cornering. During motion, the suspension system is designed to control the vertical energy transmitted by changes in the road surface or off-road terrain. To control and reduce these actions will help eliminate driver fatigue and reduce cargo damage. The other major objective of a suspension system is to keep the wheels and tires of the vehicle in constant contact with the road or terrain surface, maintaining the truck's control. The wheels and tires may lose contact with the road surface due to imperfections in its surface, which will cause vertical oscillation (up and down motion). Without suspending the vehicle separately from the frame, the vehicle would be absorbing the oscillating energy, causing the entire vehicle to accelerate this energy vertically, losing contact with the ground surface. This parabolic action will depend on the acceleration speed of the vehicle, the size of the convex (bump) or concave (pothole) irregularities of the terrain and the mass weight of the vehicle.
By introducing a means of suspension, the vehicle will maintain the wheel and tire contact with the ground surface by artificially increasing the mass weight of the vehicle by means of springs. Due to the fact that a spring under compression will try to resist this action by pushing back down on the axle plane, the greater the compression action, the greater the force of the spring that will apply in its reaction of energy. For every action, there is a reaction. The stiffness of the spring will dictate the speed of the spring. The stiffer the spring, the quicker its reaction time is, the softer the spring, the slower its reaction time is. The stiffness will also determine the travel of the spring because a quicker spring travels less than a slower spring. Suspension is a continuous, controlled action of vertical energy.
If a suspension system was comprised of only springs attached to axles, as the vertical energy would increase, its oscillation would resonate to a more rapid frequency due to the amplitude of the oscillation. The suspension system is made up of three major components, the load or sprung weight, springs (leaf and coil springs), dampers (shock absorbers), and unsprung weight (spindles and axles). The greater the unsprung mass, the less sensitive to displacement caused by the terrain irregularities, and once the vertical motion begins, it will accelerate energy and continue to do so due to the inertia factor. Another unsprung mass phenomenon is that the amplitude of wheel and tire hop becomes greater for less massive unsprung mass, meaning the wheel and tire are in contact with the ground less, and handling is adversely affected.