The suspension of the car affects its traction-dynamic characteristics and exchange rate stability. From the characteristics of the suspension depending on the carrying capacity of the car and the comfort of driving. The most common spring suspension provides good comfort, but low payload, spring suspension – on the contrary. To date, the best way to ensure high levels of comfort and load capacity is to install a pneumatic or hydropneumatic suspension on the car.
The difference of the pneumatic suspension is its elastic element – pneumatic cushion. Its feature is the ability to significantly change its stiffness, which can not be achieved by using springs or springs. The pneumatic suspension provides a constant clearance for different occupancy of the car. The pneumatic suspension is controlled either manually with the control key, or automatically. With the help of special sensors, the distance from the wheel to the body is measured, and the electronic control system compares these values with the specified ones and activates the actuators: electric motor, air suspension compressor, the receiver and the valves of the elastic element. Automatic change of the ground clearance from the speed of movement provides greater stability of the car by reducing the flow of air passing through the bottom of the body.
In general, pneumatic suspensions are installed on some basic models of minibusses, cars of increased comfort or off-road vehicles. But it is possible to install air suspension and for cars that have already been in operation. The cost of retrofitting will depend on the type of suspension that is installed on the car.
The main malfunctions of air suspension are air leakage through connecting elements, an operation of compressor rings, wear of pneumatic cushions. These problems can easily be diagnosed, as the car will sag either over individual wheels or completely. In some cars, such as, for example, Volkswagen Touareg and Porsche Cayenne, often comes out of action due to corrosion of the pneumatic fittings. This occurs most often from the action of salt and other active substances, which are sprinkled by domestic roads in winter. Since repair of the air suspension is not cheap, it is better to constantly monitor its condition and not bring it to a critical one.
Hydraulic suspension is more reliable than pneumatic. For example, the hydraulic suspension of the Mercedes “ACTIVE BODY CONTROL” has a resource of about 400 thousand kilometers, while the air suspension of the Mercedes “AIRMATIK DUAL CONTROL” – only 150 thousand km. According to the principle of operation, the suspension is similar to pneumatic. The difference of the suspension is again an elastic element. Mercedes uses hydraulic cylinders. A special fluid is used in the hydraulic system, untimely replacement of which can lead to insufficient lubrication of the pump and its increased wear, after which it can not create sufficient pressure to lift the car. Also, valve blocks fail, which will cause the car to lower after turning off the engine. Repair of hydraulic suspension is expensive since many of its components can not be repaired.
Hydroactive Suspension Citroën Hydroactive uses as hydraulic springs hydraulic racks, at the top of which are spheres with nitrogen. Also, there is an additional third sphere, which is included in the system in a comfortable mode. The latest generation of Citroen hydraulic suspensions – the Hydroactive III suspension is equipped with electronic controls, sensors, and actuators, which maintain a constant level of the body of the car, and is adjusted with speed changes. The range of changes in clearance is 30 mm.
The ability to vary the stiffness depending on the conditions characterizes pneumatic and hydraulic suspensions from the best side, but the high cost of their maintenance limits their