A shock absorber is either a mechanical or hydraulic system designed to dampen and absorb shock impulses traveling through it. It does this by transforming the kinetic energy of an initial shock into another form of energy that is later dissipated. This is done by moving the piston into a different position or motion that results in less vibration and thus less shock. In general, shock absorption or damping comes in two forms: active and passive. Each of these methods is used in different applications.
Active shock absorption comes from moving the piston out of a certain position during normal operation. The first type of shock absorption is piston-assisted suspension systems. These systems are commonly used on heavy trucks and construction equipment. They provide effective shock absorption without the use of any hydraulic or mechanical motion. The second type of active damping is spring-loaded damping. This occurs when a spring compression device (either a coil spring or hydraulic cylinder) is used to move a piston or shock absorber forward or to move it backwards when it is already in a certain position. Spring-loaded damping systems have the advantage of allowing for more precise control over damping.
The third form of passive shock absorption is called a shock absorbing tire. This is usually located under the truck's frame or beneath the vehicle's front and rear axles. This type of system is normally activated by changing a variable control unit. The purpose of this type of control unit is to allow the system to work at maximum efficiency. When driving at lower speeds, the tires work at full load and thus can dampen as much as they want. At higher speeds, the tires are under limited load and they are designed to be able to soak up as much vibration as possible. As a result, the suspension system uses less power to keep the tires on the road.