The mysterious term "clearance" is defined as the distance from the road surface to the bottom of the car. That is why instead of the concept of clearance, the phrase " ground clearance". But in addition to what the clearance of a car is, it is important to know a number of other parameters directly related to this concept.
The amount of clearance depends on the type of car and its design. The clearance of SUVs, whose main task is cross-country ability, tends to a reasonable maximum, averaging 300 mm. For cars with "sporting genes", the most important goal is to lower the center of gravity, which significantly improves handling and is determined mainly by proximity to the roadway. Their clearance value is about three times less than that of SUVs.
For passenger cars, with their practicality and asphalt “habitat”, the ground clearance is somewhere in the middle and is about 150 mm. The most compromise option is the clearance of crossovers, the value of which is about 200 mm. This ground clearance, combined with a relatively stiff suspension, defines the car's demeanor, instilling confidence in the driver, both in high-speed cornering and on moderate off-road. Add to this the ease of parking at the curb and improved visibility. No wonder crossovers are so popular. Although, in fairness, it must be said that the clearance of cars adapted for our roads is often no less than that of crossovers. So for VW Polo it is 17 cm, for Citroen C4 Sedan and Peugeot 408 - 17.5 cm, and for Lada Vesta- almost 18 cm!
Comparative clearance of cars is a loose concept. So for some machines it can be "floating", i.e. changeable. To do this, the machine is equipped with a hydropneumatic or pneumatic suspension. The range of clearance for cars with such a system is quite wide. It allows you to satisfy the ambitions of both the racer and the lover of rough terrain. This option could be considered optimal if it were not for the high price of a car with adjustable suspension. By the way, despite the bad roads, low ground clearance in our country even has its own caste of fans - the BPAN communities and the like, where car owners achieve a beautiful low landing of their cars due to handicraft installed air springs.
If desired, the clearance of the car can be changed by quite affordable methods. To reduce the clearance, the springs are replaced with shorter ones or trimmed. There are not many connoisseurs of meager ground clearance. Much more willing to increase it. The easiest way is to install wheels with a larger diameter. True, the choice of a non-standard wheel should be treated with all care. Otherwise, there is a high risk of tire friction in a turn against the body. In addition, you should immediately put up with the distortion of the speedometer and odometer readings and the incorrect operation of some electronic systems. You can increase the ground clearance with the help of interturn spacers (1000-3000 rubles per pair), which reduce the compression of the springs. That's just in combination with the inevitable in this case, a decrease in the stroke of the shock absorber, this method, although budgetary, affects the handling of the car for the worse. As well as replacing the springs with non-standard ones.
The most common is the use of spacers between the strut support and the body. Spacers can be made of rubber, polyurethane, aluminum, etc. They differ from each other in price and quality. So, rubber ones are more affordable (500–1000 rubles), but less wear-resistant. Polyurethane (1000–4000 rubles) last longer, but are more expensive and can deform the body. And aluminum (1000–2000 rubles) can cause corrosion at the junction. It should be borne in mind that an increase in clearance by more than 30-40 mm threatens the unpredictability of the car's behavior on the road, especially in corners, as well as increased wear and failure of some chassis components, such as expensive CV joints, due to the increased angle of the drive shafts.
Before embarking on radical transformations to increase the vehicle's ground clearance, it would be useful to study its bottom on a lift. Depending on the design, it may have many protruding parts or be relatively smooth. Perhaps, according to the results of the “revision”, it will be possible to calculate weak spots design and develop an individual style of operation, taking into account the existing standard clearance. In addition, you should remember about the size of the wheelbase. Sometimes a car with low ground clearance and a short base is more passable than its long-wheelbase opponent with impressive ground clearance.
And further. Although the crankcase is usually the lowest point of the machine, it is worth protecting it with metal or Kevlar protection. Yes, the ground clearance in this case will decrease by 10–15 mm, but insurance will appear against an unforeseen breakdown of the crankcase and, as a result, expensive repairs.
In many cities, roads that are slowly falling into disrepair are rarely repaired, and where yesterday the car passed freely, today it begins to touch the bottom of the bumps, as a result of which the owner thinks about how to increase the ground clearance. But despite the fact that everyone would like to solve the problem with a minimum of effort and financial resources, not every method is safe for the vehicle itself. Let's take a look at a few of the methods used.
How to increase ground clearance in front of the bottom of the car
Not a single vehicle, except, perhaps, a trolley, has an absolutely smooth bottom, there is always a protruding part, the distance from which to the roadway is called clearance, according to GOST. But where is the lowest point? In the area of protruding parts of the engine compartment from below? Among and shock absorbers? Or maybe this exhaust system? In fact, any knot under the car can be caught on a stone or earthen hill, and it is difficult to think of a better way out, except to increase the ground clearance.
The part of the car closest to the obstacle in the way is the front bumper.. Despite the fact that this detail is somewhat higher than many others, it may suffer in the first place. For passenger cars, the ground clearance to the bumper is from 14 to 20 centimeters, for SUVs this gap corresponds to 18-25 centimeters, and for full-fledged SUVs - 20-35 centimeters. You can increase the clearance in this place by removing the so-called "skirt" that protects the bumper, but this will increase its vulnerability. However, instead of a protruding safety pad, parking sensors are often used.
Which is better - cars with variable ground clearance or increased?
Overcoming an obstacle, forcing the car to literally go on tiptoe, albeit at the expense of a fair amount of speed reduction - isn't this the dream of every driver? However, vehicles that have nodes to increase the clearance at will are somewhat more expensive than models that do not have such a function. And only a few can afford cars with variable clearance. But how convenient: the speed is reduced to 20 kilometers per hour, the toggle switch is pressed, liquid is pumped into a special cushion between the body and the shock absorber by hydraulics, and the clearance increases. When the speed increases, the car itself sags to its previous position.
But what about those who do not have such a system? You can raise it artificially, however, it is not always safe. In particular, inter-turn prefixes can be installed in the suspension springs, as a result of which, under the weight of the body, the elastic elements will compress less, but be prepared for an increase in the rigidity of the movement. Installing more powerful springs reduces the rebound travel of the shock absorbers, and at the same time quickly disables these components. Motorists sometimes install aluminum attachments between the body and the pillar support, but there is a drawback here too - such elements provoke corrosion with the salt mixture that is used to treat icy roads. The best option- installation of rubber attachments instead of aluminum ones.
Is it really necessary to increase the clearance of the car?
The greatest risk area is the oil pan. This is where the lowest point is usually located. At the same time, damage to the pallet always has the most unpleasant consequences for the motorist. The clearance of cars in this place is 12-17 centimeters, SUVs - within 17-21 centimeters, and SUVs - abroad 20 centimeters. However, increasing the clearance of the car by removing the protection, although not difficult, is quite dangerous, on the contrary, it is better to sacrifice one or two centimeters by installing an additional shield made of carbon fiber or thin metal.
The clearance may also decrease, since the springs tend to sag over time, and by replacing them, you can get the same clearance.
Another area that is often tested for strength by various uneven terrain is the exhaust system. Since it runs under the bottom, it is constantly subject to impacts, and the further the system is from the surface of the landscape, the better. Also vulnerable rear suspension, can be easily damaged cardan shaft all-wheel drive vehicle. Unfortunately, it is impossible to close all these nodes, however, having carefully studied their location, while driving, it will not be difficult to avoid breakdowns on rough roads, skipping hills under safe areas of the bottom.
In the 21st century, the era of nanotechnology, modern drivers still have to try on the "skin" of off-road conquerors. Broken roads, pits, rails and steep curbs - just not full list obstacles that we have to overcome every day. Alas, sometimes our car lacks some centimeters. As a result - a rattle, an annoying scratch on the bumper and ... the inevitable repair. Is it possible to counter this by changing the ground clearance of your car? And is it realistic to do this without becoming the object of close attention of the traffic police? Let's find out.
The main goal of changing the ride height is to improve the vehicle's patency. Of course, the topic of improving cross-country ability is the lot of off-road enthusiasts who are trying day and night to increase the travel and performance of suspension elements. But not only for the sake of overcoming road troubles, car owners want to refine their suspension. Some Practical drivers resort to this method in order to increase the carrying capacity. And young people, on the contrary, lower the suspension of the car for better handling, and sometimes for the sake of frank "show-offs".
It should be noted here that for the sake of security traffic From June 1, 2014, the operation of cars is prohibited in Russia, the ground clearance of which does not correspond to their passport data. As noted in the traffic police, first of all, this rule is aimed at those drivers who underestimate the ground clearance and thereby “slow down” the flow of cars when driving through road bumps. The same rule applies to them as to any other car owner who has made changes to the vehicle design that are not provided for by the manufacturer. For this today, an administrative fine of 500 rubles is threatened.
Therefore, everything that is written below is by no means a guide to action. This is more of an educational program for those who decide to make an exhibition sample out of their car for some kind of auto show. Or participate in trophy raids, overcoming obstacles somewhere in the impassable wilderness. Ride on such a modified vehicle on public roads is prohibited.
Springs and dampers
This type can be called the simplest and cheapest. After all, in fact, to change the ground clearance of the car, it is enough just to replace the struts, consisting of springs and shock absorbers with the characteristics we need. This "reset" will allow you to change the clearance up or down. But, nevertheless, for yourself you need to understand the following. There are two types of shock absorbers - hydraulic and gas-hydraulic (often called gas-filled or simply gas). In hydraulic shock absorbers, vibration damping occurs due to the flow of liquid (usually oil) from one reservoir to another and back through a special valve system, which ensures sufficient smoothness and ultimate comfort for the driver. In the second type of shock absorbers, liquid is also present, but it is pre-compressed with a small volume of gas. Gas shock absorbers make the suspension travel stiffer and the car feels more manageable on the road.
Springs are standard and reinforced, raising and lowering. The standard ones are designed for average operating conditions, and the reinforced ones - due to increased compression - help to better overcome country roads. Lowering and raising allow you to change the clearance of the car. The former are necessary to increase the clearance of the car, due to an additional turn and contribute to its better cross-country ability. The latter, as the name implies, reduce the ground clearance of the car and improve its handling at high speeds.
The primary advantages of such changes include their low cost, a noticeable increase in improved road performance and sufficient reliability. The replacement operations themselves can be performed independently. But keep in mind that increasing shock absorbers and springs can adversely affect the stability of the car at high speeds, while lowering ones, on the contrary, will worsen patency on our roads. And this is a very serious disadvantage.
The most famous and popular springs and shock absorbers from manufacturers such as DEMFI, KYB, SS20, SAAZ, KONI, MONROE, SACHS, etc.
The cost of shock absorbers and springs as an assembly is low: about 3,500 rubles per set. The threshold ends in tens of thousands of rubles. But here it is worth paying attention to manufacturers. Indeed, on the market, these spare parts are most susceptible to counterfeit production. Therefore, when buying, check the integrity of the package. Spare parts must not contain chips, cracks, shells and traces of corrosion. Avoid shopping at junkets and one-day markets. Remember that the handling of the car directly depends on the suspension, and with it your life.
Spacers
These special devices are installed between the suspension elements. The front spacers are designed in the form of a box-bracket with mounting holes, and the rear spacers are made in the form of rings with three lugs. The materials from which the spacers are made can be different - metal, plastic, polyurethane, or a combination.
The advantage in upgrading the suspension with spacers is that they allow you to increase the clearance of the car and "return" the clearance to its original position when the springs shrink from the increase in carrying capacity. Plus, installation is also not a problem. It is quite possible to do it yourself or use the services of a service center.
However, spacers do have their downsides. The increased clearance shifts the center of gravity of the car upwards, which will undoubtedly affect the stability of the car and its handling. The stiffness and reliability of the suspension changes for the worse due to changes in camber, toe and angle of rotation of the wheels. The wear of the steering units is increasing, the operation of the suspension shock absorbers is changing.
A set of spacers (2 pcs.) in automotive stores and markets costs from 1000 rubles, depending on the brand of car and manufacturer. Spacers from manufacturers such as ABS, Leoni, PC "Polymer", etc. are in the greatest demand. When buying, be sure to require a certificate of conformity or a patent for these products to make sure that you are not looking at frank "handicraft".
Air suspension
All of us, for sure, have seen cars in movies or videos on the Internet, the suspension of which rises or lowers at the request of the driver. The magic of what is happening lies in the fact that the suspension of the cars is pneumatic. Currently, this type of suspension is not outlandish and is serially installed on a number of business class cars, trucks and even semi-trailers.
As the consultant of the Togliatti tuning company "LowFamily" told Volga News Alexander Isaev, simplified air suspension consists of special pneumatic elements on each wheel of the car: a compressor, receivers, air lines and control electronics. "The compressor supplies compressed air to the receiver and actuators that regulate the vehicle's ground clearance. Air lines connect all parts air suspension into one system. And the electronic unit, using special sensors, "scans" the parameters of the position of the body, its inclination, acceleration of the car and adjusts the suspension," Alexander explains.
Installation of such a system can be made on almost any type of suspension - from MacPherson struts to a complex "multi-link".
Air suspension can be one-, two- and four-circuit. A single-circuit system is placed on any of the axles of the car, allowing you to adjust the rigidity depending on the load on the car. The system with two circuits allows you to install both on one and on two axles at once. The four-circuit system can be attributed to the most complex systems, since it uses an electronic control unit that takes control "on itself" in automatic mode. But due to the complexity of installation and high cost, such a system is rarely used in Russia, and even more so in Samara.
In order not to get confused in the complex installation of compressors, pneumatic elements and risers, it is better to leave this work to professionals who will be able to mount all the elements of the air suspension and set it up correctly. With self-installation, the air suspension will only have the function of changing the height of the body.
The main advantages of the air suspension are a high level of comfort, safety and cross-country ability, due to the smoothness of the ride and the absence of noise due to the operation of compressed air. Among the shortcomings, it is worth noting the sufficient high cost of buying air suspension elements and installing it with constructive changes. The fattest minus can be called low maintainability and exposure to road chemicals and low temperatures in the winter. “Also, the disadvantages of the air suspension relate to the periodic revision of the system,” notes Alexander Isaev.
“Air suspension should be installed in cases where you have a “show car”, for lowering and spectacular appearance and so that the car can “dance,” advises Alexander Isaev. “It is also suitable if you have a jeep and there is a need increase the ground clearance. And if it's a truck, then such a suspension will be very useful so that when loaded it does not sag or roll."
The cost of a pneumatic system depends primarily on the number of circuits. A single-loop system will cost much less than a two- or four-loop system. But, in general, the price of such a refinement of the suspension is much higher than the previous options. Plus, the final cost is superimposed good price for installation work. On average, the price range starts from 40 thousand rubles for a complete set of all four wheels and ends at the level of 100-120 thousand. It is worth choosing components from the world-famous companies Viair, AirLift, Stinger, etc. “When choosing, you should pay attention to the manufacturer of pillows and other components,” the specialist explains. bodies".
The design of the car is always controversial. The engineer is forced to choose between a variety of factors, sometimes directly opposite. So, for good cross-country ability, you need a large clearance, and aerodynamics (and, therefore, top speed and fuel consumption) it only hurts. For comfort, a soft suspension is good, but it does not achieve polished handling. Etc. That is why attempts to combine the mutually exclusive properties of the car together do not stop.
One of these attempts resulted in the creation of an adjustable suspension. Its essence lies in the ability to change the ground clearance of the car on the go, thereby radically changing its properties.
High ground clearance (and, as a result, a high center of gravity) is incompatible with good exchange rate stability, so it is impossible to quickly take turns on an SUV. And vice versa: low ground clearance, short-stroke suspension and its rigid setting put a bold cross on the use of a car on the road.
This contradiction is exactly what the adjustable ride height is designed to solve. A car with this option is able to change the center of gravity and aerodynamics on the go (it is known that it depends very much on the height of the car). In addition, its off-road properties can also be changed at the touch of a button, or even without driver intervention, automatically. The ability to arbitrarily change the ground clearance also gives a side effect - a car with such a device can maintain a constant ground clearance regardless of the level and nature of its load (that is, the distribution of cargo over the car), which has a positive effect not only on the stability of the car, but also on the distribution headlight beam.
Regulation algorithm
For safety reasons, the ride height control system must necessarily have automatic modes, which could prevent dangerous maneuvering (both highway driving at high speed with a "raised vehicle" and driving on broken roads or rough terrain with a "lowered vehicle"). And such systems are indeed being established. So, when a certain speed is reached (usually 35 km / h), the vehicle's ground clearance automatically switches from the highest position to a step lower (of course, if the ground clearance was set to any other position than the highest, switching does not occur). At a speed of 80 km / h and above, the car automatically switches to the "normal level" of clearance. If the vehicle is moving faster than 120 km/h, the ride height is automatically reduced to a low level. Thus, it is possible to reduce aerodynamic drag, improve handling by lowering the center of gravity and reduce fuel consumption.
High levels of ground clearance, on the contrary, usually do not have automation and are turned on forcibly, with a button.
System Composition
Lifting and lowering of the car are carried out with the help of pneumatic elastic elements. When air is supplied to them under pressure, they change their volume and raise the car. Bleeding air, you can lower the car.
The system often has a receiver that allows you to start lifting the car body immediately after starting the engine, without waiting for the pressure to rise in the system, and also reduces the noise from the compressor.
For the full and correct operation of the system, it must include ride height sensors. The sensor is attached to the body and through a special lever is connected to lower arm pendants. Any vertical movement of the body relative to the wheel (and hence the suspension) causes movement of the sensor arm, which is converted into a rotational movement. The rotational movement is detected by an inductive sensor, which generates an electrical signal proportional to the angle of rotation of the lever. Using the readings of the sensors, the system monitors the position of the car and eliminates possible distortions in the operation of the pneumatics, that is, it controls the uniformity of lifting and lowering the body, as well as its position relative to the ground plane or roadway. Clearance sensors help the system eliminate vehicle skew (for example, due to different air supply on the left and right).
Variable ride height vehicles are also equipped with automatic dynamic headlight range control. Since ride height sensors are part of the system, their readings can be used to automatically maintain the headlight beam at a constant level. In order to exclude too frequent operation of the corrector when driving over bumps, the system reacts to changes in sensor readings without mechanically repeating the terrain, it analyzes these readings and works with a large delay, calculating some average position of the body relative to the surface.
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Transport » The project of a service station with the development of a site for the repair of the running gear of cars for the State Institution sanatorium "Primorye" st. Okeanskaya Vladivostok » Determining the need for electricity, heat and water
The first suspension with variable ground clearance for a passenger car was created by the French company Citroen. The elastic element in the shock absorbers was compressed nitrogen, and the power element (forming and transmitting pressure in the system) was liquid. Therefore, such a suspension is called hydropneumatic. The hydraulic pump pumps liquid from the reservoir, and the spheres fixed next to the shock absorber. Inside each, liquid and gas are separated by a membrane. Thus, the necessary pressure is maintained in the shock absorbers, and the rolls of the machine are constantly compensated. In addition, a crane built into the hydraulic system allows you to adjust the amount of fluid circulating in the circuits, which means increasing or decreasing ground clearance.
In 1954, this scheme was first applied to the high-end model "Citroen 15-6". And already in October 1955, the company's novelty - "Citroen DS" - caused a real sensation at the 42nd Paris Motor Show. At the time, it was a miracle machine. Its hydropneumatic suspension ensured constant ground clearance regardless of the number of passengers and luggage and a stunningly smooth ride. This car could roll forward and backward, as well as hang any wheel without a jack! And finally, the driver of the Citroen DS could, at his own discretion, stepwise change the ride height. This not only increased stability and active safety car on the highway (the center of gravity lowered, the air flow under the bottom, which creates lift, decreased), but it also made it easier to drive off-road, which is important for France, which abounds with country roads.
Subsequently, such a suspension scheme was used on most Citroen cars and was improved all the time. The latest development of the company - the Hydroactive III suspension - received electronic control using sensors, computer and actuators. As a result, the clearance of the Citroen C5 model is not only maintained, but also automatically adjusted depending on the speed, quality pavement and driving style. The range of changes in ground clearance reaches 20-30 mm. "Citroen" made hydropneumatic suspension his "horse", applying it before others. However, the British Leyland Motor Corp. installed a similar Hydrolastic suspension on its small cars, and Lotus developed hydropneumatics for the Scorpion reconnaissance tank.
In Russia, an airborne combat vehicle (BMD) with a hydropneumatic independent suspension Since 1968, all rollers have been produced by the Volgograd Tractor Plant. The car had to lower the bottom of the body to the ground, so that it is better on the ground and easier to load into the aircraft. Studying the possibilities of using a purely air suspension in cars many firms have been involved. For example, in the 60s "Daimler-Benz" ("Mercedes - Benz 600" and "Lincoln" equipped it production models. And the first SUV equipped with wheel suspension on "air bags" that replaced the springs was in 1992 " range rover LSE. Great research in this area was carried out in the 70s by Volkswagen and Audi together with Fichtel und Sachs.
As a result, in the spring of 2000, Audi launched the all-wheel-drive Allroad model with independent air suspension of the wheels, equipped with an electronic control unit. At speeds above 120 km / h, the clearance is set to 142 mm, at a speed of 80 km / h - 167 mm, and below the car rises 192 mm above the road. In addition to automatically changing the clearance, it is possible to manually change it, allowing the driver to “raise” the car to a height of 208 mm.
Similar to " Audi Allroad The air suspension design was given to the all-wheel drive Volkswagen AAC concept car: it has an independent long-travel suspension on double wishbones. The range of ground clearance with three fixed positions is simply huge - from 280 mm to 390 mm. Currently "Toyota" for its SUV " Land cruiser 100 (aka Lexus LS400) offers Automatic High Control (AHC) as an option. The change in clearance occurs in four fixed positions by 50 mm down or up from the base value of 220 mm. Position switching occurs within 7 seconds after the driver presses a button on the center console.
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