Car shock absorbers - what is a shock absorber and how does it work?

A shock absorber is a damping device that is used on a car to effectively absorb shocks and shocks, dampen vibrations, etc. Also, the shock absorber (car strut) allows you to press the wheel to the road when driving on rough roads, thereby improving traction properties, increasing braking efficiency, vehicle stability, etc.

Today there are several types and types of shock absorbers, which differ not only depending on the axis on which they stand (front shock absorbers or rear shock absorbers), but also in design terms.

Next, we will look at what a shock absorber is and what a car's shock absorber is. So, within the framework of the article, a separate emphasis is placed on what types of shock absorbers there are on cars, types of struts, how they differ, and also the advantages and disadvantages of various types of struts, etc. are considered.

What is a shock absorber

A modern shock absorber is a complex mechanism that dampens vibrations, absorbs shocks and ensures constant contact of the wheels with the road surface when the car is moving. It is installed next to the wheel. Using a lever system, mechanical loads (shocks and vibrations) are transmitted from the rotating wheel to the mechanism.

This part is equipped with a spring, which ensures quick return of the rod after compression when hitting a bump. If this process does not occur quickly, then the car will become uncontrollable off-road.

Diagnosis

The slightest suspicion of a malfunction requires immediate diagnostic work. There are measures that a car enthusiast can do on his own, which will be the first test of the struts.

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Some car owners do without testing at the stand and spontaneously rock their vehicles in order to determine the shock absorbers. True, this check is very ineffective, since the weakening and performance of the racks does not affect the swaying of the vehicle, in the end it seems that everything is in order.

The history of the shock absorber

As transport evolved, designers came to the conclusion that, in addition to a powerful and efficient power unit with a durable body, the car needed a good suspension that would soften the impact of uneven roads. The first shock absorbers had an unpleasant effect - while driving they strongly rocked the vehicle, which caused the steering to suffer greatly.

Spring shock absorbers partially damped body vibrations due to the friction force between the sheets, but this effect was not completely eliminated, especially when the vehicle was heavily loaded. This prompted designers to develop two separate elements. One was responsible for softening the impacts from the wheel on the body, and the other restored the contact patch of the wheel, springing it, quickly bringing the damper element to its original position.

At the beginning of the last century, a separate damping suspension element was developed. It was a dry friction shock absorber, which included friction discs. The first piston oil telescopic shock absorbers appeared in the 50s of the last century. The basis of their work was the principle of fluid friction.

The design of such shock absorbers was borrowed from the design of an aircraft landing gear. This type of shock absorber design is still used today.

Silent blocks

All moving suspension elements are attached to the body through rubber inserts - silent blocks. They dampen vibrations from one part to another. They consist of two metal bushings with a rubber element between them. Due to its plasticity, vibrations during operation of moving parts of the chassis are dampened and their mobility is ensured.

For example, if there were no silent block at the place where the lever is attached to the frame, the lever would rub against the frame. This connection increased the wear of the metal and produced a terrible squeak when the car moved. In addition, any impacts on the wheel from the road were transmitted to the body, you would hear knocking noises. This would quickly break the fastening unit.

Therefore, when independently diagnosing a car’s suspension, pay attention to the condition of the silent blocks. They should not have cracks or damage. There are times when the inner bushing peels off from the rubber and begins to dangle and knock.

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Shock absorber design

Most shock absorbers consist of the following components:

Steel hollow tube (cylinder). On one side it is muffled. An eye is welded to this part, which allows you to secure the stand to the wheel hub. The reservoir is filled with liquid (a mixture of gas and liquid or gas only), which compensates for the load when the piston is compressed. A rod seal is installed on the open side, preventing fluid from leaking out of the cavity.
Shock absorber rod. This is a steel rod, the cross-section of which depends on the model of the mechanism. It is placed in a tank. On one side, the rod is attached to a support bearing, and on the other, a piston placed inside the cylinder is attached to it.
Piston. This element moves inside the cylinder, creating pressure on the liquid or gas inside the tube.
Bypass valve. It is mounted on the piston and has several holes with spring-loaded valves. When the piston moves, one group of valves is activated, ensuring flow from the cavity under the piston to the part above it. Smooth running is ensured by resistance due to small holes (the liquid does not have time to move quickly between the cavities). A similar process occurs during the recoil stroke (when the piston rises), only in this case the valves of another group are activated.

The design of modern damper mechanisms is constantly being improved, which increases their efficiency and reliability. The design of shock absorbers can differ significantly depending on the modification of the mechanism. However, the operating principle remains unchanged. When pushed, the rod moves the piston inside the cylinder, which compresses the liquid or gas.

Sometimes shock absorbers are confused with gas springs, which are installed on the trunk lid or on the hood. Although they look similar, they each serve a different function. Dampers dampen shocks, and gas springs ensure smooth opening and retention of heavy lids in this position.

What is the difference between shock absorbers and struts?

The shock absorber and strut are attached differently. The rack design eliminates the need for an upper ball joint and linkage. It is attached to the lever and ball only at the bottom, and at the top it is installed in a support bearing.

The shock absorber itself is attached using silent blocks without a support bearing. The rod of the strut has a large diameter, while the rod of the shock absorber has a small diameter. Thanks to this method of fastening, the rack is able to absorb multidirectional loads, and the shock absorber - only along its axis. The shock absorber may be part of the strut.

Why are shock absorbers needed?

When creating vehicles, early developers faced a serious problem. While driving on the road, the driver experienced terrible discomfort from constant shaking. In addition, due to the loads, parts of the chassis quickly failed.

To eliminate the problem, they began to put rubber hoses spread out lengthwise on the wheels. Then springs appeared that dampened bumps, but the vehicle lacked stability. On bumps the car swayed violently.

The first shock absorbers appeared in 1903, and were made in the form of springs attached to levers near each wheel. They were mainly installed on sports cars, since horse-drawn vehicles did not need such a system due to low speeds. Over the years, this development has been improved, and friction shock absorbers have been replaced by hydraulic analogues.

When driving on uneven surfaces, the wheels of the vehicle must be in constant contact with the surface. The controllability of the vehicle will depend on the quality of the shock absorber.

When the car accelerates, the body tilts backwards. Because of this, the front part of the car is unloaded, which reduces the traction of the front wheels with the road. During braking, the reverse process occurs - the body leans forward, and now the contact of the rear wheels with the ground is broken. When turning, the load moves to the opposite side of the car.

The task of shock absorbers is not only to dampen shocks, providing maximum comfort for the driver, but also to maintain the car body in a stable horizontal position, preventing it from swaying (as was the case in cars with spring suspension), which increases vehicle controllability.

Consequences of wear

If there is a skid, we can conclude that the shock absorber has become unusable.

Consequences Failure of the shock absorber system can lead to the following troubles:

loss of control.
a large passage of the path followed by crashing during heavy braking.
decrease in directional stability.
reduction in carrying capacity.
failure of other suspension parts.
feeling every bump, hole, while driving.

Types and types of automobile shock absorbers

All shock absorbers are divided into three types:

Hydraulic. The reservoir contains oil, which, under the action of the piston, flows from one plane of the reservoir to another.
Gas-hydraulic (or gas-oil). In their design, the compensation chamber is filled with gas, which reduces the likelihood of bottom breakdown due to excessive load.
Gas. In this modification, gas under pressure in the working cylinder is used as a damper.

In addition, damper mechanisms are divided into:

single-pipe;
two-pipe;
adjustable.

Each modification has its own design and operating principle.

Monotube (mono-tube) shock absorbers

Single-pipe modifications are a new generation of damping mechanisms. They have a simple design and consist of:

a flask partially filled with oil and gas (among single-pipe models there are completely gas ones);
a rod that moves the main piston inside the cylinder;
the piston mounted on the rod is equipped with bypass valves through which oil flows from one cavity to another;
a separating piston separating the oil chamber from the gas chamber (in the case of gas-filled models, this element is absent).

Such modifications work according to the following principle. As the oil in the reservoir is compressed, the piston valves open. The pressure at the bottom of the cylinder is reduced by fluid flowing through small holes in the piston. The rod gradually lowers, compensating for shocks while the car is moving.

The gas cavity is filled with nitrogen. Due to the high pressure (over 20 atm), the piston does not reach the bottom of the cylinder, which reduces the likelihood of the shock absorber breaking through large bumps.

Twin-pipe types of shock absorbers

Today this is the most common category of shock absorbers. They consist of the following elements:

A body into which another flask is placed. In the space between the walls of the vessels there is a gas and compensation cavity.
The bulb (or working cylinder) is completely filled with shock-absorbing fluid. There are inlet and outlet valves at the bottom.
The rod pushing the piston is the same as in the single-pipe version.
A piston equipped with bypass valves. Some open when the piston moves down, and others open when it returns up.

Such mechanisms work according to the following principle. The rod presses on the piston, causing oil to flow into the upper part of the working cylinder. If the pressure increases sharply (the car hits a bump - a strong shock occurs), then the bottom valves of the working flask are activated.

The leaked oil into the compensation cavity (the space between the walls of the working cylinder and the housing) compresses the air located in the upper part of the chamber. Stabilization of rebound forces occurs due to the operation of piston and bottom valves, through which the oil moves back into the working chamber.

Combined (gas-oil) shock absorbers

This type of shock absorbers replaced the previous type. The design of the mechanisms is identical to the hydraulic modifications. Their only difference is that in combined damper struts the gas is under pressure of 4-20 atmospheres, and in hydraulic struts it is under normal atmospheric pressure.

This is called gas boost. This modernization allows automakers to improve the handling of their cars. The gas boost serves as an additional compensator, increasing the efficiency of the rack. Front and rear damper struts may require different gas pressures in the compensation cavity.

Adjustable shock absorbers

This type of shock absorbers is installed on expensive cars equipped with a road surface selection function. Such mechanisms are identical to two-pipe modifications, only they have an additional reservoir. It can be located next to the rack, or it can be made in the form of another tube placed inside the housing (forms an additional baffle cavity).

Such shock absorbers work in tandem with a pumping station, which changes the pressure in the gas cavity, giving the suspension the desired characteristics. Changes in parameters are monitored by electronics. Adjustment is made from inside the car using the appropriate control knobs. Here are the most common types of settings:

Standard. The shock absorber is operating normally. The suspension with this setting is soft, which makes the ride more comfortable. In this case, the shock absorber travel is significantly greater than with other settings. Potholes on the road are practically not felt in the cabin.
Comfort. The gas pressure in the compensation chamber increases slightly, providing increased rebound rigidity. Most drivers use this feature. It is considered the “golden mean” between ride comfort and car handling.

Highway. The rod stroke in this mode becomes even shorter. It is turned on for driving on smooth roads. This setting exposes any deficiencies in steering precision (if any). The machine will behave more softly when heavily loaded.
Sport. If you drive on regular roads in this mode, the driver may soon need a chiropractor. The car body accurately conveys every bump in the road, as if the car had no suspension at all. However, the presence of this mode allows you to check how well the car is made. The steering feels responsive. Minimum body sway ensures maximum traction.

Expensive car models are equipped with such shock absorbers. They are also used for professional tuning. With the help of such a suspension, you can not only change the rebound stiffness, but also change the vehicle's ground clearance.

More primitive adjustable shock absorbers look like a regular two-pipe combination. The strut body has a thread on which a stop for the spring is screwed. This modification is called a coilover. Adjustment is made manually using a wrench (turning the support nut, moving it either up or down).

Watch also a video about the design and classification of shock absorbers:

Shock absorber. Device, difference, purpose, gas, oil.

Which shock absorbers are better

Each type of shock absorber has its own advantages and disadvantages. The ideal option is to select struts and springs in accordance with the recommendations of the machine manufacturer. “Soft” models will provide increased comfort during the trip, but at the same time reduce the grip of the wheels on the road. With “hard” ones, the opposite effect is observed - the stability of the car is improved by reducing comfort for the driver and passengers.

1. Monotube. The advantage of such damper struts is:

High precision machine control. They prevent the car from swaying and reduce roll when cornering.
They can be installed upside down. Gas pressure and oil do not mix thanks to the floating piston.
The working cylinder is cooled more efficiently because the air blows directly onto its walls. Due to the absence of a housing, the size of the piston and reservoir are increased, due to which the range of operation of the shock absorber is expanded compared to twin-tube analogues.

Among the disadvantages are the following:

Vulnerability to damage. Since they are not equipped with a shell, even a slight deformation of the flask leads to failure of the entire mechanism - the piston can no longer move freely inside the tank. The only solution to this problem is to replace the rack.
High sensitivity to changes in ambient temperature. The warmer it is outside, the higher the gas pressure, which increases the stiffness of the suspension.

2. Two-pipe. The advantages of this modification are:

Simple design, which makes them cheaper than previous analogues.
The working cylinder is protected from external damage. The rack body serves as a buffer.
They belong to the category of “soft” shock absorbers.

The disadvantages include the following factors:

High oil aeration. The air in the gas cavity is under atmospheric pressure, so it is easier for liquids to mix with it. The problem does not go away even when replacing regular air with nitrogen.
Poor cooling. The working cylinder, in fact, has a double shell, due to which, when the piston rubs, the oil heats up, its fluidity increases, and the shock absorber becomes even softer.

3. Combined. Since gas-oil shock absorbers are an improved version of conventional twin-tube shock absorbers, their advantages and disadvantages are the same. Their main difference is the absence of aeration due to high pressure in the gas supply.

4. Adjustable. This category of dampers is the next step in the evolution of the car's adaptive suspension. Their advantages:

Adjustment of damper operation to the appropriate road surface. This will allow you to choose the optimal position between vehicle stability and ride comfort.
Budget coilovers are easy to adjust - just turn the retaining nut to compress or loosen the spring. More expensive automatic models provide fine-tuned suspension firmness. In this case, it is enough to move the regulator to the appropriate position. Some models allow you to adjust the front and rear struts separately.

If the vehicle was not equipped with adaptive suspension from the factory, installing it may damage the mounting location of the strut. Changing the factory characteristics of a car can improve the performance of the car, but at the same time significantly reduce the service life of various suspension and chassis parts.

When choosing between oil and gas-filled shock absorbers, you should pay attention to:

cost - gas ones are more expensive than oil ones;
comfort and durability - the gas version is stiffer than the oil version, so it is not suitable for traveling on country roads, but they last longer than the liquid version;
car controllability - the gas-filled version is ideal for sports driving, as it ensures vehicle stability on turns and small inclines, and also reduces braking distance. Oil-filled models are designed for measured driving, since at high speed, due to sway and roll, traction with the road deteriorates.

Here is another video that will help you determine which shock absorber is better:

Which shock absorbers are better and more reliable - gas, oil or gas-oil. Just something complicated

Sports

Designed to withstand high loads. The working fluid is temperature stable and does not lose viscosity when heated. To maintain constant adhesion of the wheels to the road, they have an increased compression force and a short rebound time, which ensures constant adhesion of the wheels to the road and good handling on turns.

How to check shock absorber struts

To determine if the racks are faulty, you need to follow a simple procedure. At speeds between 20-30 km/h. press the brake sharply. If the shock absorbers have exhausted their service life, then the car will “peck” forward, or the rear part will noticeably jump.

You can also check the suspension on bumpy and winding roads. If the car begins to sway more than usual, then the service life of the struts has expired and they need to be replaced.

Another way to check shock absorbers is on a vibration stand. This procedure will help determine what condition the mechanisms are in and how urgently they need to be changed.

The need for replacement appears as a result of natural wear and tear of parts, as well as due to excessive loads on the damper mechanism (frequent overloads and fast driving over potholes).

Shock absorber life

Each part of a car or motorcycle has its own working resource. This is especially true for mechanisms that are regularly subjected to heavy loads. The service life of shock absorbers directly depends on the accuracy of the driver (he avoids potholes or rushes over them at high speed), the condition of the roads and the weight of the car.

The average car operated in the CIS needs to replace shock absorbers after approximately 60-70 thousand kilometers. In this case, it is recommended to carry out diagnostics every 20 thousand.

Malfunctions and how to identify them?

Visually, shock absorber malfunction can be identified by the nature of damping during driving. If the car begins to sway unnaturally when driving on uneven roads, then the shock absorbers should be diagnosed. To do this, first of all, you need to inspect the condition of the shock absorbers and their anthers.

A failed damper will be coated with oil (the working fluid has leaked out of the container). Oil leaks on the body or boots are a reason to replace the shock absorber. The performance of this part is checked by trying to swing the car body in a vertical direction (press and release several times, trying to increase the amplitude of the vibration, applying more effort each time). A working shock absorber will prevent the car from swaying and will stop the oscillation almost immediately.

Bench testing

If you are unsure of the accuracy and correctness of your own conclusions regarding the proper operation of the racks, it is recommended to rely on specialists who perform diagnostics on a vibration stand. Naturally, the verification procedure is paid, but with the help of verification, you can get an opinion from specialists and precise instructions for the next action.

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To avoid wasting money, you should use the following tips:

Check the computer settings by technicians to diagnose a specific vehicle model.
Taking into account the age of the machine, the weight of the body, settings and standards may have certain discrepancies.
Check wheel alignment and tire pressure before the test.
Contact a good service center that suits you individually.

Checking the racks is not as simple as it might seem initially; it is a very difficult and laborious process, taking into account every little thing and detail.

How to replace shock absorbers

Replacing shock absorbers is carried out in the following sequence.

Raise the car on a lift. If it is raised with the help of jacks, then when changing the front shock absorbers, the car must be put on the handbrake, and when installing the rear ones, the gear must be engaged (in rear-wheel drive cars, the front wheels must be blocked in a different way, for example, using wheel chocks).
Unscrew the fastening on the steering knuckle.
When replacing the front struts, the steering tip is removed.
Unscrew the rod mount on the support bearing.

The rack is installed in the reverse order.

The example of a VAZ 2111 shows how the procedure is performed:

Replacing front shock absorbers VAZ

Recommendations from professionals:

Before installing a new strut (applies to a two-pipe modification), the shock absorber must be pumped so that the air leaves the working cylinder. If this is not done, then “dips” of the piston will appear while driving. Pumping is carried out as follows: the shock absorber, turned upside down, is smoothly compressed, fixed for 2-3 seconds, in this state it is turned over and after 3-5 seconds. release smoothly. Then the rack is turned over with the rod down, wait a couple of seconds, and repeat the procedure three or four times. After bleeding, the shock absorber should be stored in a vertical position, just as it will be installed on the car.
Do not use a pneumatic impact wrench to tighten the rod mount. Because of this, the rod may turn and damage the seal. If this does not happen, over-tightening will create tension in the shock absorber rod, due to which it may break over a large bump.
It is strictly forbidden to fix the rod with pliers or other clamping tools. This will damage the rod mirror. To fix it, use a special key.
Before final tightening of the rod nut, the vehicle must be lowered from the lift or jack. This way the rod will be twisted evenly and will not break or break the silent block while driving.

Motorists disagree about the comprehensive replacement of shock absorbers. Some believe that all the racks need to be changed at once, while others are sure that replacing the damaged part is enough.

Although each motorist decides for himself how to repair his car, experts insist on pair replacement - even if one is faulty, then replace both on the side (either front or rear). Due to fatigue wear, old parts combined with new ones can significantly reduce the efficiency of the entire assembly. In any case, remember: one faulty part can negatively affect other important suspension or chassis components.

When to change

Here are the cases in which it is definitely necessary to change the racks:

as a result of a visual inspection, traces of liquid leakage were revealed on the body;
deformation of the rack body;
The stiffness of the suspension has increased - noticeable impacts to the body occur on potholes;
the car sagged noticeably (most often one shock absorber fails, so the car will sag on the corresponding side).

The following video shows one of the options on how to diagnose a suspension fault yourself:

Tips for Drivers - How to Diagnose Shock Absorbers (Chassis)

If a knocking sound occurs in the suspension, you should immediately contact a service station. Such changes in the car cannot be ignored, because the safety of not only the owner of the damaged car, but also other road users depends on them.