All shock absorbers work on the following principle: inside the shock absorber cylinder there is a rod with a piston, which "walks" in oil. When the shock absorber is working, 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 liquid, causing the gas to be compressed.
When air is used as a gas, this shock absorber is called hydraulic ("Soviet" shock absorbers "SAAZ"). The disadvantage of air is that it "foams the oil" with constant shaking, and with stronger shaking, low-pressure bubbles can appear, which significantly reduces the efficiency of the shock absorber.
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).
The solution was found when the French engineer De Carbon pumped nitrogen into the compensating chamber under a pressure of more than 20 atmospheres and separated the nitrogen from the oil with a piston gasket, which does not allow the nitrogen and oil to come 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 accurately.
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 "crumbs".
Recently, new developments have emerged. For example, the company "Koni" produces shock absorbers with adjustable stiffness. The most sophisticated one allows you to do this directly from the cabin. Such "steepness" is installed on the Maserati car. In turn, the company "BOGE" has developed a system of automatic ground clearance regulation (the "Nivomat" system). Its meaning is that when the car is loaded, it "sags" and its ground clearance (clearance) changes. As soon as the car is loaded, the vibrations of the wheels during movement activate the pump built into the shock absorber design. 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 after driving over any bump starts to swing dangerously, you can even catch your belly on the asphalt. The shock absorber may jam, then the car turns into a "stool". If this happens, then even a baby understands - the shock absorbers need to be replaced or repaired.
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 damaged shock absorbers. And what is happening in the CIS countries with our roads is completely unknown.
But 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 the shock absorber 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 drives into a puddle with a 6 mm layer of water, the aquaplaning effect (when the car "floats" above the surface and becomes uncontrollable) 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 skidding on sharp turns. Also, worn shock absorbers cause many parts of the car to fail: tires, springs, wheel suspensions, ball joints, etc.
Often, motorists think about replacing the shock absorber only when oil starts leaking from it: "the struts are leaking - I'll have to replace them somehow." But this is the last stage of life (or rather, already death!) shock absorber. It is not recommended to let the car get to this state. And to check the operation of shock absorbers, it is not necessary to go to special stands. You just need to "squeeze" each corner of the car and if after the rocking there is more than one full oscillation, then the shock absorbers "will not hold up". They need to be replaced.
Manufacturers recommend checking the condition of the shock absorber after every 20 thousand km of vehicle mileage.
So, you've decided to replace your shock absorbers. But how to choose? Remember that shock absorbers largely determine the nature of the car's handling. By replacing the shock absorber, you can transform a soft suspension into a sporty one. If you are at high speeds, for example, on the "eight", and you are irritated by excessive body swing, our advice: buy shock absorbers of a sporty nature (Koni, Bistein and etc.), but be aware that the suspension will probably be firm, 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 SAAZs, or you can buy products from foreign companies.
Owners of foreign cars have a choice between "native" shock absorbers, that is, those that are supplied directly to the assembly line of the manufacturer, and products from companies working 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 the factory ones.
But replacing shock absorbers is not such a simple matter. There are many subtleties and tricks here. And that is why many companies provide a guarantee only if the product is installed correctly at service centers.
Now about guarantees. A normal city warranty should be 1 year, regardless of mileage. We would recommend buying shock absorbers in brand stores, not in markets. Of course, it's cheaper at the markets, but then you have to change the racks every six months. As the saying goes, a miser pays twice.
Let us 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, etc.
- BOGE - produces hydraulic and gas shock absorbers. Supplied to BMW, Saab, Volvo.
- MONROE - ranks first in Europe in terms of sales of shock absorbers to the secondary market. Manufactures low pressure hydraulic and gas filled shock absorbers. Supplied to Volvo.
- GABRIEL is an American company. Second place in Europe in terms of 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. Supplied to some German cars, such as Mercedes-Benz.
- KONI - elite Dutch shock absorbers. They are supplied to Ferrari, Porshe. They are used in Formula 1, IndyCar racing. Shock absorbers of this company are also used in front-wheel drive 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 vibrations of the vehicle. 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 damper element; like liquid - (oil shock absorbers), so is gas (gas shock absorbers).
The single-tube shock absorber is characterized by a high degree of reliability, low sensitivity to overloads, and non-criticality to the installation position. The disadvantages include the dependence of the degree of damping 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 low pressure atmospheric 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 verified 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 obtain 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 development) are used to extend the range of driving comfort and increase safety. Controlling the damping parameters, on the other hand, leads to the establishment of a link between comfort and safety.