The shock absorber is divided into two main types: hydraulic and inflatable from the perspective of the material that produces the damping, and there is also a variable damping shock absorber.

Hydraulic shock absorbers
Hydraulic shock absorbers are widely used in automotive suspension systems. The principle is that when the frame and the axle reciprocate relative to each other, the piston moves reciprocating in the cylinder barrel of the shock absorber, and the oil in the shock absorber housing repeatedly flows from the inner cavity through some narrow pores into the other inner cavity. At this time, the friction between the liquid and the inner wall and the internal friction of the liquid molecules form a damping force on the vibration.

Inflatable shock absorbers
The gas-charged shock absorber is a new type of shock absorber developed since the 60s. Its structural feature is that a floating piston is installed in the lower part of the cylinder barrel, and a closed air chamber formed between the floating piston and the cylinder barrel is filled with high-pressure nitrogen. The floating piston is equipped with a large cross-section O-ring, which completely separates oil and gas. The working piston is equipped with compression valves and extension valves that change the cross-sectional area of the channel with the magnitude of its movement speed.
When the wheel jumps up and down, the working piston of the shock absorber reciprocates in the oil species, so that the oil pressure difference between the upper and lower chambers of the working piston is generated, and the pressure oil pushes the compression valve and the extension valve back and forth. Due to the large damping force generated by the valve on the pressure oil, the vibration is attenuated.

Resistance adjustable
The suspension of cars equipped with drag adjustable shock absorbers generally uses gas springs with variable stiffness as elastic elements. The principle is that if the air pressure of the air spring increases, the pressure in the air chamber of the shock absorber also increases, and the throttle aperture of the oil changes due to the change of pressure, so as to achieve the purpose of changing the damping stiffness
Shock absorber is a vulnerable accessory during the use of the car, the shock absorber works well or badly, will directly affect the stability of the car driving and the life of other parts, so we should make the shock absorber often in good working condition. The following methods can be used to check whether the shock absorber works well.