Mercedes of the S-class W202
1993-2000 of release
Repair and operation of the car
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Lubrication system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. System of ignition
+ 8. Fuel system
+ 9. Transmission
- 10. Running gear
+ 10.1.2. Shock-absorbers
+ 10.1.3. Forward springs
10.1.4. Stabilizer of cross 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. Electrical circuitries
To understand why the shock-absorber 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 antiquity. Other alternatives of a spring – a pneumosuspension bracket of "Citroën" or a hydropneumosuspension bracket of Rover which use the compressed gas. But we will return to a spring. At movement along the road the car begins to be shaken, and it is inadmissible. The main task of the shock-absorber also consists in extinguishing these fluctuations, or to damp.
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 during the operation of the shock-absorber flows through a special opening of the piston. It also creates the necessary resistance to the movement of a rod. Also in the shock-absorber there has to be a container (the compensatory camera) with the compressed gas (air or nitrogen). In the shock-absorber the piston goes and forces out surplus of liquid, forcing to contract gas.
When as gas air is used, this shock-absorber call hydraulic (the "Soviet" shock-absorbers SAAZ). The lack of air is that it at continuous jolting "makes foam oil", and at stronger jolting there can be bubbles of low pressure that considerably reduces overall performance of the shock-absorber.
Instead of air nitrogen is often used. Sometimes it is downloaded under low pressure in several 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 bubbles of low pressure).
Exit was found when the French engineer De Carbon pumped in the compensatory camera nitrogen under 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 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 were new developments. For example, Koni 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 BOGE developed system of automatic control of a road gleam (Nivomat system). Its sense that when the car is loaded, he "sinks" and it changes a road gleam (clearance). As soon as the car is loaded, fluctuations of wheels at the movement put the pump which is built in a shock-absorber design in action. This pump after several hundred meters restores a necessary road gleam. After unloading the car the pump is automatically adjusted at an old size of a road gleam.
The shock-absorber is that part of the car of which you do not think until until it breaks. 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 begins 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, then and it is clear to the baby – 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 damaged shock-absorbers. And what becomes in the CIS countries with our roads – in general it is unknown.
And shock-absorbers influence not only comfort, but also traffic safety. Here it is pertinent to give results of work of the independent research organization "Tuv Rheinland" which carried out expertize about influence of the shock-absorber on traffic safety.
When braking at a speed of 50 km/h on the dry road with one shock-absorber which is worn out for 50%, the brake way of the car increases by two meters. It is a lot of or a little – to judge to you. But as there are also not enough often these two meters for avoidance of the tragedy.
When the car with the shock-absorbers which are 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 a 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 many details of the car out of action: tires, springs, suspension brackets of wheels, spherical support, etc.
Often motorists think of replacement of the shock-absorber only when from it oil begins to flow: "racks began to flow – it will be necessary to replace somehow". But it is already the last stage of life (more true, already death!) shock-absorber. It is not recommended to bring the car to this state. And to check operation of shock-absorbers, it is optional to go to special stands. It is only necessary "to prozhat" each corner of the car and if after the muscleman there are more than one full wave then, shock-absorbers "will not sustain". They should be replaced.
Manufacturing firms recommend to check a condition of the shock-absorber after each 20 thousand km of a run of the car.
So, you decided to replace shock-absorbers. But how to choose? Remember that shock-absorbers in many respects determine the nature of controllability by the car. Replacement of the shock-absorber it is possible to turn a soft suspension bracket into sports. If you at 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, perhaps, 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 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 those which are delivered directly on the conveyor of manufacturer, and production of the firms working for the secondary market. There are shock-absorbers especially for used cars. Such production is usually much cheaper than "family", and quality and characteristics of such products are not worse, and sometimes and better, than factory.
But replacement of shock-absorbers not it simple business. There are a lot of subtleties and cunnings. And therefore many firms give a guarantee only at the correct installation for service centers.
Now about guarantees. The normal guarantee on the city has to make 1 year, irrespective of a run. We would recommend to buy shock-absorbers in company shops, but not 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 bought.
SACHS – is the European leader in delivery of shock-absorbers to the conveyor. Is established serially on BMW, Audii other.
BOGE – makes hydraulic and gas shock-absorbers. It is delivered on BMW, Saab, Volvo.
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 product sales in the secondary market. Makes gadravlichesky and gas shock-absorbers.
KAYAVA – the Japanese firm. Production is delivered on many conveyors of the Japanese car makers. Also shock-absorbers for cars of the European production are issued.
DE CARBON – the French firm, the first Mc Ferson which released gas shock-absorbers of high pressure for a 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. They are used in "Formula One", races Indikar. Shock-absorbers of this firm are used also in front-wheel VAZs.