Dampening - A dampener, a piston filled with air or hydraulic fluid, controls the rate of compression and rebound. A tiny hole in the piston determines how fast it can be moved through the fluid or air. Changing the hole or valve size affects the piston's rate of compression and rebound. One-way valves allow compression and rebound dampening to be controlled independently. Users can manually adjust the amount of shock absorption for some pistons.
Pneumatic springs are air-filled and operate like a piston.
Dampeners can limit the rate at which a coil or pneumatic spring will compress on rebound. Spring rate - A typical shock absorber, which comes in a variety of lengths and ranges of travel, consists of a hydraulic dampener and a spring. Spring rate and dampening ratios should be set according to the height and spacing of a trail's bumps and how fast you will be moving over them. Pressurization - Some pneumatic pistons require a specified amount of pressurization to operate correctly. In some cases the piston must be pressured up to 200 psi.