Air shock absorbers, also known as air suspension, use pressurized air bladders to adjust a vehicle's ride height and firmness. An air compressor, either engine-driven or electric, pumps air into flexible rubber bellows, which are then slipped over the shocks. When the air volume in the bladders changes, the vehicle rises or lowers.
Air suspension systems can be useful for a number of reasons, including:
Off-roading
Air suspension can increase ground clearance
Entry and exit
Air suspension can lower the ride height for getting in and out of tall vehicles
Performance
The rate of an air spring can be adjusted at any time, which can improve ride quality or performance
Work applications
Ride height and pressure can be important for work applications, such as keeping a pickup truck loaded with heavy cargo suspended
Air springs are progressive, meaning that increased compression makes the spring stiffer. Ride-height systems monitor how much the car rises and lowers, and the pressure needed to reach each level. Some systems can even remain active for a short time after the vehicle is turned off to compensate for temperature differences.