S-class W202 Mercedes
1993-2000 of release
Repair and car operation
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Greasing system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. Ignition system
+ 8. Fuel system
+ 9. Transmission
- 10. Running gear
+ 10.1.2. Shock-absorbers
+ 10.1.3. Forward springs
10.1.4. Stabilizer of cross-section stability
+ 10.2. Zadny Bridge
10.3. Why the shock-absorber is necessary
10.4. Types of shock-absorbers
10.5. Additional protection of spherical hinges of steering drafts
10.6. "Cunning" bolts and nuts
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electroschemes
To understand, the shock-absorber why is necessary, – try to do a bit of traveling without it...
In order that the car did not perceive all roughnesses on the road, in a suspension bracket of the car any elastic element is surely used. Usually применятеся spring. Besides a spring, the spring can be used, but it is already full архаика. Other alternatives of a spring – pneumosuspension bracket of "Citroen" or a hydropneumosuspension bracket of "Rover" which work at the compressed gas. But we will return to a spring. At movement on the road the car starts to be shaken, and it is inadmissible. The main task of the shock-absorber also consists in extinguishing these fluctuations, or демпфировать.
All shock-absorbers work by such principle: in the cylinder of the shock-absorber there is a rod with the piston, which "goes" in oil. Oil at operation of the shock-absorber flows through a special opening of the piston. It also creates necessary resistance to rod movement. Also in the shock-absorber there should be a capacity (the kompensatorny chamber) with the compressed gas (air or nitrogen). In the shock-absorber the piston goes and forces out surpluses of liquid, forcing to be compressed by gas.
When as gas air is used, this shock-absorber call hydraulic (the "Soviet" shock-absorbers "SAAZ"). A lack of air that it at continuous jolting "makes foam oil", and at stronger jolting there can be vials of low pressure that considerably reduces overall performance of the shock-absorber.
Instead of air nitrogen is often used. Sometimes it download under low pressure in some atmospheres. Such shock-absorbers call gazonapolennny low pressure. But nitrogen under low pressure does not solve a cardinal problem of "oil foaming" and cavitation (that is formations of vials of low pressure).
The exit was found, when De Karbon's French engineer pumped in the kompensatorny chamber nitrogen under the pressure of more than 20 atmospheres and separated nitrogen from oil laying piston which does not allow nitrogen and oil to contact among themselves. It removed a problem of foaming of oil and cavitation. Nitrogen under a high pressure allows valves of the piston to work silently and quickly, and also creates additional effort on a rod. Such shock-absorbers work effectively and precisely.
Gas-filled shock-absorbers are not recommended to be used by small cars as the additional effort to a body, rendered by such shock-absorbers, is harmful to "crumbs".
Recently there was new development. For example, the Koni firm makes shock-absorbers with rigidity adjustment. Most "fancy" allows to do it directly of salon. Such "steepness" is put on the Maserati car. In turn the BOGE firm developed system of automatic control of a road gleam (Nivomat system). Its sense that when the car is loaded, it "gives" and at it is changed a road gleam (road clearance). As soon as the car is loaded, fluctuations of wheels at movement put in action the pump which has been built in a design of the shock-absorber. This pump after several hundred meters restores a necessary road gleam. After unloading the car the pump is automatically adjusted on old size of a road gleam.
The shock-absorber is a that part of the car on which you do not reflect until while it will not break. As soon as the shock-absorber "was covered", we realize, as without it it is bad and as with it it is good.
The car with idle shock-absorbers after journey of any hillock starts to be shaken dangerously, it is possible even to hook a belly on asphalt. The shock-absorber can and jam, then the car turns into "stool". If it occurred, and to the baby it is clear – shock-absorbers should be changed or repaired.
But usually shock-absorbers wear out gradually and the driver of it does not notice. By estimates of the western experts, in Europe about 30 % of cars are more senior than 5 years go with the spoiled shock-absorbers. And that becomes in CIS countries with our roads – in general it is not known.
And after all shock-absorbers influence not only comfort, but also on traffic safety. Here pertinently to give results of work of the independent research organization "Tuv Rheinland" which examined about influence of the shock-absorber on traffic safety.
When braking for speeds of 50 km/h on the dry road with one shock-absorber which has been worn out for 50 %, the brake way of the car increases by two meters. It is a lot of it or a little – to judge to you. But as it is frequent these two meters and does not suffice for tragedy avoidance.
When the car with the shock-absorbers worn out for 50 % drives in a pool with a sheet of water in 6 mm, the effect of hydroplaning (when the car "emerges" over a covering and becomes uncontrollable) comes at speed of 81 km/h. At normal shock-absorbers this speed equals 85 km/h. Besides the above-mentioned, the "killed" shock-absorbers increase risk of demolition of the car on abrupt turns. Also worn-out shock-absorbers put out of action many details of the car: tires, springs, suspension brackets of wheels, spherical support etc.
Often motorists reflect on shock-absorber replacement only when from it oil will begin to flow: "racks began to flow – it will be necessary to replace somehow". But it already the last stage of life (is more true, already death!) shock-absorber. To this condition to lead up the car it is not recommended. And to check operation of shock-absorbers, it is unessential to go on special stands. It is necessary only "прожать" each corner of the car and if after the muscleman will be more than one full wave then, shock-absorbers "will not sustain". It is necessary to replace them.
manufacturing firms recommend to check a shock-absorber condition after each 20 thousand km of run of the car.
So, you decided to replace shock-absorbers. But how to choose? Remember that shock-absorbers in many respects determine nature of controllability by the car. Replacement of the shock-absorber it is possible to turn a soft suspension bracket into the sports. If you on high speeds, for example, on "eight", you are irritated by an excessive swing of a body, our council: buy shock-absorbers of sports character (Koni, Bistein, etc.), but know that the suspension bracket, probably, will be rigid, and the profile of the road will be transferred in detail sitting in salon.
The "Soviet" shock-absorbers, of course, are cheaper than the foreign. And owners of "our" cars can choose. It is possible to buy SAAZES, and it is possible to buy production of the foreign companies.
At owners of foreign cars the choice lies between "native" shock-absorbers, that is what are delivered directly on the manufacturer conveyor, and production of the firms working for the secondary market. There are shock-absorbers specially for second-hand cars. Such production is usually much cheaper "native", and quality and characteristics of such products is not worse, and sometimes and better, than factory.
But replacement of shock-absorbers not such simple business. There are a lot of subtleties and cunnings. And consequently many firms give a guarantee only at the correct installation on service centers.
Now about guarantees. The normal guarantee on the city should make 1 year, irrespective of run. We would recommend to buy shock-absorbers in firm shops, instead of in the markets. In the markets, of course, cheaper but then racks it is possible to change each half a year. As they say, penny-wise and pound-foolish.
Let's give the characteristic of the main producers of shock-absorbers, whose goods can be got.
SACHS – is the European leader on delivery of shock-absorbers to the conveyor. It is established serially on BMW, Audiи other.
BOGE – makes hydraulic and gas shock-absorbers. Volvo is delivered on BMW, Saab.
MONROE – wins first place in Europe on realization of shock-absorbers on the secondary market. Makes gadravlichesky and gas-filled shock-absorbers of low pressure. It is delivered on Volvo.
GABRIEL – the American firm. The second place in Europe on production realization in the secondary market. Makes gadravlichesky and gas shock-absorbers.
KAYAVA – Japanese firm. Production is delivered on many conveyors of Japanese automakers. Shock-absorbers for cars of the European production are issued also.
DE CARBON – the French firm, the first let out gas shock-absorbers of a high pressure for Mc Ferson suspension bracket.
BILSTEIN – sports shock-absorbers. Mersedes-Benz are delivered on some German cars, for example.
KONI – elite Dutch shock-absorbers. Are delivered on Ferrari, Porshe. Them use in "Formula-1", races Indikar. Shock-absorbers of this firm are used also in front-wheel VAZs.