Dampers (Shock Absorbers)
A suspension system with only springs to absorb and suspend the truck's vertical travel would find itself out of control. The purpose of shock absorbers is to control the compression, extension, and frequency of the truck's suspension. A suspension must have balanced suspension shock absorbers to fine-tune the system. The coil springs and leaf springs support the vehicle's weight while the shock absorbers control the velocity of the spring action. Besides damping the initial shock of either a spring's compression, the extension of the shock absorber will damp or decrease the amount of vibrations by absorbing the wheel and tire impacts on the road and terrain imperfections.
A coilover shock is constructed with the coil spring sandwiched between an upper and lower
A shock absorber will slow down and control the compression and extension frequencies (rapid vertical movement). A basic shock absorber consists of a canister (body), a shaft, and a piston. The piston is connected to the shock shaft. It travels up and down inside the shock body, which is filled with a hydraulic fluid or a mix of hydraulic fluid and gas nitrogen, which helps dissipate heat that builds up due to the friction of the shock's oscillating action. This helps eliminate cavitation (foaming of the hydraulic fluid). With the help of hydraulic action, the shock travel is damped. The amount of time it takes a shock to go back to its normal or static ride height is referred to as rebound. By controlling each wheel and tire, vertical travel frequencies will keep the truck's overall suspension under control.
As a truck's suspension is lowered, the amount of travel within the shock absorber is also decreased. The internal design of a lowered truck shock is different than that of a stock ride height shock. Because of the shorter travel, the lowered shock valving is altered. To help control the shock absorber's frequencies, the shock body is filled with a hydraulic fluid (a petroleum-based oil) that is moved through a series of valves while a single piston controls the shock shaft travel.
Types of Shock Absorbers
Twin TubeThe twin tube moves the fluid in and out of two separate chambers that act as reservoirs by opening and closing valves at the bottom of the shock. As pressure is increased by compressing the hydraulic fluid, it forces the fluid through the holes or valve in the shock piston.
Mono Tube
The shock has a single, high-pressure chamber that exchanges the fluid from one side of the piston to the other by means of valves of fluid flexing discs on the piston head itself.
Gas Filled
This is used to pressurize the shock tube with nitrogen gas, which improves its ability to the resistance of compression and extension of the shock's travel. This will improve the shock's ability to control oscillation. Higher gas pressures can eliminate cavitation entirely when used in a mono-tube design.
IAS (Inertia Active System):
IAS is new design developed by Edelbrock. The shock is a mono-tube design similar in appearance to the Bilstein shock. These IAS shocks are filled to 280 psi of nitrogen gas to prevent cavitation. The secret is in the valving system, a moving part attached to the piston assembly that is called an inertia valve, which allows the shock to behave according to the type of input it receives. The inertia valve is a heavy piece of bronze that floats above the piston, suspended on springs that balance its weight against gravity.
When the piston or rod moves sharply downward in rebound, the inertia valve tends to stay at rest, floating on top of the piston assembly. The shock is valved normally for compression, but when the piston begins to move downward, powered by the buildup of the spring energy, the inertia valve stays put and then follows the travel of the piston downward, opening the orifices between the valve and piston to allow oil to flow through. It's still metered, but the flow is higher than with the valve closed in the default position. As soon as the tire is planted again on the ground, the valve resumes its normal position and the shock is metered through the piston only. The result is that the tire remains planted on the ground, regardless of the nature of the terrain.