Shock absorbers dampen vibrations and reduce shocks, which are transferred to the bodywork as a result of deformation of elastic suspension elements when the wheels run over uneven road surfaces. Most of today's cars are both passenger cars, and trucks, it is equipped with hydraulic shock absorbers. Other types of shock absorbers are almost out of use. The principle of operation of a hydraulic shock absorber is based on the use of hydraulic resistance, obstructing the flow of liquids (oil), to dampen vibrations, and sometimes to limit the deformation of elastic suspension elements. For shock absorbers, a liquid is usually used, consisting of 40% transformer oil i 60% spindle oil. In terms of operation, hydraulic shock absorbers are divided into: - single-acting (rarely used); they resist expansion of the spring, , double-acting i (the most commonly used); they resist both compression, and depressurization, however, their action is not equally intense in both directions, when the car wheel is lifted, their resistance is smaller and equals 1/4-1/2 resistance to the drop of the wheel. In terms of construction, shock absorbers are divided into lever and telescopic.