All shock absorbers operate on the following principle: inside the shock absorber cylinder is a piston rod that "floats" in oil. When the shock absorber operates, the oil flows through a special hole in the piston. This creates the necessary resistance to the movement of the rod. The shock absorber must also have a capacity (compensatory chamber) with compressed gas (air or nitrogen). A piston moves inside the shock absorber and displaces excess fluid, causing the gas to be compressed.
When air is used as the gas, the shock absorber is called a hydraulic shock absorber (like the Soviet-era SAAZ shock absorbers). The disadvantage of air is that it "foams the oil" under constant vibration, and under more severe vibration, low-pressure bubbles can form, significantly reducing the shock absorber's efficiency.
Nitrogen is often used instead of air. Sometimes it is pumped under low pressure of several atmospheres. Such shock absorbers are called low-pressure gas-filled. But low-pressure nitrogen does not solve the fundamental problem of "oil foaming" and cavitation (that is, the formation of low-pressure bubbles).
A solution was found when the French engineer De Carbon pumped nitrogen into the compensation chamber under pressure of more than 20 atmospheres and separated the nitrogen from the oil with a piston gasket, which prevented the nitrogen and oil from coming into contact with each other. This eliminated the problem of oil foaming and cavitation. High-pressure nitrogen allows the piston valves to operate silently and quickly, and also creates additional force on the piston rod. These shock absorbers work efficiently and precisely.
Gas-filled shock absorbers are not recommended for use on small cars, as the additional force exerted on the body by such shock absorbers is harmful for the "little ones".
New developments have emerged recently. For example, the company "Koni" produces shock absorbers with adjustable stiffness. The most sophisticated one allows you to do this directly from the cabin. This "steepness" is put on a Maserati car. In turn, the company "BOGE" has developed a system of automatic control of ground clearance (system "Nivomat"). Its meaning is that when the car is loaded, it "sags" and its ground clearance (ground clearance) changes. As soon as the car is loaded, the vibrations of the wheels during movement activate the pump built into the shock absorber structure. This pump restores the required ground clearance after just a few hundred meters. After unloading the vehicle, the pump automatically adjusts to the old ground clearance value.
The shock absorber is that part of the car that you don't think about until it breaks. As soon as the shock absorber "breaks down", we realize how bad it is without it and how good it is with it.
A car with non-working shock absorbers begins to sway dangerously after driving over any bump, and its belly can even hit the asphalt. The shock absorber can jam, which can turn the car into a "stool." If this happens, even a baby knows the shock absorbers need to be replaced or repaired.
For details, see the website (MazBook)
But usually shock absorbers wear out gradually and the driver does not notice it. According to Western experts, in Europe about 30% of cars older than 5 years are driven with faulty shock absorbers. And what is happening with our roads in the CIS countries is completely unknown.
After all, shock absorbers affect not only comfort, but also driving safety. It is appropriate here to cite the results of the work of an independent research organization "Tuv Rheinland", which conducted an examination of the impact of shock absorbers on traffic safety.
When braking at 50 km/h on a dry road with one shock absorber worn out by 50%, the braking distance of the car increases by two meters. Whether this is a lot or a little is up to you to judge. But how often are these two meters precisely what is missing to avoid tragedy?.
When a car with 50% worn shock absorbers enters a puddle with a water layer of 6 mm, the aquaplaning effect (when the car "floats" above the surface and becomes uncontrolled) occurs at a speed of 81 km/h. With normal shock absorbers, this speed is 85 km/h. In addition to the above, "killed" shock absorbers increase the risk of car demolition on sharp turns. Worn shock absorbers also cause damage to many vehicle components: tires, springs, wheel suspension, ball joints, etc.
Drivers often only consider replacing a shock absorber when it starts leaking oil: "The struts are leaking—I'll have to replace them sometime." But that's the final stage of their life (or rather, already death!) shock absorber. It is not recommended to let the car reach this state. And to check the operation of shock absorbers, it is not necessary to go to special stands. You just need to "press" each corner of the car, and if after a roll there's more than one full oscillation, then the shock absorbers won't hold up. They need to be replaced.
Manufacturers recommend checking the condition of the shock absorber after every 20 thousand kilometers of the vehicle's mileage.
So, you've decided to replace your shock absorbers. But how do you choose? Remember that shock absorbers largely determine a car's handling. By replacing the shock absorber, you can transform a soft suspension into a sporty one. If you are driving at high speeds, for example, on a "figure eight", and you are irritated by excessive body roll, our advice is to buy sports shock absorbers (Koni, Bistein, etc.), but be aware that the suspension may be stiff, and the road profile will be transmitted in detail to those sitting in the cabin.
"Soviet" shock absorbers are, of course, cheaper than foreign ones. And the owners of "our" cars can choose. You can buy SAAZ trucks, or you can buy products from foreign companies.
Foreign car owners have a choice between "original" shock absorbers, that is, those supplied directly to the manufacturer's assembly line, and products from companies operating in the secondary market. There are shock absorbers specifically for used cars. Such products are usually much cheaper than the original ones, and the quality and characteristics of such products are no worse, and sometimes even better, than factory ones.
But replacing shock absorbers is not such a simple matter. There are many subtleties and tricks here. That's why many companies only provide a warranty if the product is installed correctly at a service center.
Now about the guarantees. A normal city warranty should be 1 year, regardless of mileage. We would recommend purchasing shock absorbers from brand stores rather than from markets. It's cheaper at the markets, of course, but then you have to change the racks every six months. As the saying goes, a miser pays twice.
Let's describe the main manufacturers of shock absorbers whose products can be purchased.
SACHS is the European leader in the supply of shock absorbers to the assembly line. Installed as standard on BMW, Audi and others.
BOGE – produces hydraulic and gas shock absorbers. Available for BMW, Saab, Volvo.
MONROE is the number one supplier of shock absorbers to the aftermarket in Europe. Manufactures low-pressure hydraulic and gas-filled shock absorbers. Supplied to Volvo.
GABRIEL is an American company. Second place in Europe for sales of products on the secondary market. Produces hydraulic and gas shock absorbers.
KAYAVA is a Japanese company. The products are supplied to many assembly lines of Japanese automakers. Shock absorbers for European-made vehicles are also produced.
DE CARBON is a French company that was the first to produce high-pressure gas shock absorbers for McPherson suspension.
BILSTEIN – sports shock absorbers. They are supplied to some German cars, for example, Mersedes-Benz.
KONI – elite Dutch shock absorbers. They are supplied to Ferrari and Porsche. They are used in Formula 1 and IndyCar racing. Shock absorbers from this company are also used in front-wheel drive vehicles VAZs.
Shock absorbers are divided into two main types according to their design: twin-tube and single-tube shock absorbers.
Monotube shock absorber
1. Atmospheric pressure.
2. Valve regulating compression resistance.
3. Valve regulating tensile strength.
4. Bypass valves.
Twin-tube shock absorber
1. Atmospheric pressure.
2. Backup camera.
3. Basic one-pipe system.
A damper is an additional mass that provides springiness and dampens vehicle vibrations. The damper assimilates the vibrations of the main system, that is, the main system stops vibrating – the movement is limited by the vibration damper. Dampers minimize body movements. Can be used as a damping element; like a liquid – (oil shock absorbers), and gas too (gas shock absorbers).
The single-tube shock absorber is characterized by a high degree of reliability, low sensitivity to overloads, and non-criticalness to the installation position. The disadvantages include the dependence of the damping degree on the compression parameters (which in the latest developments is compensated by installing additional bypass valves in the piston) and the fact that the monotube shock absorber is a long type shock absorber.
Twin tube shock absorber is technologically known as atmospheric, low pressure operating twin tube type.
Advantages: insensitive to external damage. Here, unlike a single-tube shock absorber, mechanical impacts can also be absorbed by the outer tube; the adjusted position of the machine is limited to the area of the body structure. This is a short type of shock absorber because the balance chamber is located behind the working cylinder.
Disadvantages: the shock absorber is sensitive to overload (damping stops). Only certain installation positions are possible, precision matching of pipe diameters.
The damping characteristics are the result of the combined damping function of the orifice and the spring loaded valve that closes the orifice; the spring responds to pressure by increasing the free aperture of the outlet hole. The piston bore and spring can be specially adapted to ensure the linearity and softness of the damping function. An internal adjustment mechanism is used to achieve multiple operating characteristics for an individual shock absorber. Compression ratio values are often only 30...50% of the rebound capacity.
Shock absorbers with electronically adjustable characteristics (active refinement) are used to extend the range of driving comfort and increase safety. Controlling damping parameters, on the other hand, leads to the establishment of a link between comfort and safety.