The car's suspension includes guiding elements, elastic and damping. They ensure the correct displacement of the wheels in relation to the body, springing and converting the energy of vibrating motion into heat and dissipating it to the environment. The suspension characteristics are always a compromise between two substantially contradictory requirements – comfort ("softness") and driving safety ("hardness"). From the point of view of kinematics, there are dependent suspensions, in which the movements of one wheel of a given axle affect the movements of the other wheel and are independent, in which both wheels move independently of each other.
ADVANTAGES AND DISADVANTAGES OF TRAILING LONGITUDINAL ARMS In passenger cars, as a rule, at the front, and the back often, independent suspensions are used. One of the solutions, especially advantageous in front-wheel drive vehicles, is the guidance of the rear wheels on longitudinal trailing arms and their suspension with coil springs or torsion bars. Such a system is compact, it does not take up much space and does not reduce the useful space of the boot, whose floor can be flat. The relative movements of the wheels also take place parallel to each other in the vertical plane, while maintaining a constant spacing, toe-in and minimal change in tilt angle. However, the wishbones undergo transverse deformation, causing an increase in the sideslip angles of the rear wheels, which in turn worsens the car's stability. To avoid this unfavorable phenomenon, from mid-years 70., especially in lower and middle class cars, and recently also higher (np. Audi A6), the so-called. coupled wishbone system.