What gives the pumping of tires with nitrogen. Injection of nitrogen into tires - are there real benefits? Is there an effect of nitrogen in tires

These are the headlines that many truck and passenger tire changers are full of.

Nitrogen is a stable tire pressure!Significant reduction in tire pressure fluctuation, regardless of vehicle speed, load and ambient temperature

I pumped up the tire with nitrogen - check your tire pressure three times less often!

Nitrogen is economical and safe! Reducing the likelihood of tire explosion.

Nitrogen - prevents tire aging!

Nitrogen in tires is the reduction of noise and vibration from the contact of the tire with the road surface,increasing the smoothness and softness of the passage of irregularities in the road surface, improving traction with the road surface and reducing the braking distance

Tire nitrogen - reduces wear on truck and car tires and ensures even wear

Nitrogen in the tire is a decrease in the load on the car's suspension, improved wheel shock absorption

The advantages of pumping tires with nitrogen do not end there, you also "get:"

- Improving car handling

- Improved stability when cornering, changing lanes and exits

- Reducing wheel slip during emergency start

- Improving the performance of wheels at increased loads and temperatures

- Reducing the likelihood of disc damage when falling into a pit, hitting a curb, etc.

- Elimination of oxidation processes of the tire metal cord and disc material

The benefits of using nitrogen have long been appreciated by Western Europe. There, in tire workshops and specialized centers, such a service is a common thing.

This topic is especially relevant for truck drivers who use solid-metal cord tires with a very high internal pressure (about 8 bar) on their Euro trucks.

However, it is not harmful for the driver of a car to know that a tire inflated with nitrogen keeps the pressure more evenly. This means that when the tire heats up too much in summer or when the ambient temperature drops significantly in winter, there is no sudden change in tire pressure. And that too high or low pressure is harmful to the tires, there is no need to explain. If a tire costs 12-18 thousand rubles, then spending a little money on maintaining its "health" is a sacred cause.

In addition, the natural pressure drop occurs more slowly in a tire inflated with nitrogen. This process occurs constantly at the molecular level, and since the nitrogen molecules are large enough, they are less likely to pass through the molecular structure of rubber. In this case, wheel pumping is required less often.

The air we breathe and fill our lungs and tires contains about 21% oxygen and 78% nitrogen.

Oxygen is harmful to rubber. First, it accelerates aging. Secondly, oxygen penetrates through the thinnest holes, "flows out" from the most sealed reservoirs, and hence from the tire. Nitrogen does not come out of the tire as easily as air, that is, the pressure loss is much lower than when the tire is filled with air. It is also known that pressurized oxygen in a tire accelerates rim corrosion. Oxygen contributes to damage to the sidewalls and carcass of tires.

Filling tires with nitrogen, i.e. without oxygen, reduces the moisture in the tire, which increases its durability. The advantages of filling tires with nitrogen have long been known and have been used until now mainly for filling tires of trucks and buses, as well as in all cases where it was necessary to achieve special properties of tires, for example, when reaching record speeds of cars.

Although there are no official regulations for filling tires with nitrogen yet, many tire services are already offering this service widely to their customers.

After filling tires with nitrogen became widespread for tires of trucks, buses, tractors, now widespread use of nitrogen begins for tires of passenger cars. The effectiveness of using nitrogen instead of air for filling tires is based on the fact that it is a "noble" (inert) gas, it does not contain dust, oil, wet particles, and other components that reduce the durability of the wheel. Therefore, nitrogen is synonymous with safety for tires and those who use it. The advantages of using nitrogen to inflate tires are as follows:

1. There is no oxidation process of the tire steel cord. Oxygen in the air is an oxidizing agent, and high humidity inside a tire inflated with air leads to moisture condensation at temperature extremes. Together, these factors lead to corrosion of the steel cord and therefore reduce the life of the tire. The moisture content of nitrogen is close to zero; moreover, it is not an oxidizing agent.
2. The pressure in a tire inflated with air changes sharply depending on the current temperature of the tire, and in summer, naturally, this pressure reaches its maximum values. The coefficient of thermal expansion of air is large: for a wheel of a car, the increase in tire pressure can reach 0.5-0.8 atmospheres. Under load, the slightest bump on a car tire can cause an explosion, and if the front wheel bursts, the result will be unpredictable. For nitrogen, the coefficient of thermal expansion is much lower: as a result of heating, the pressure in the tire changes by only 0.1 atmospheres, therefore, the stability of the pressure inside the tire at any temperature is ensured.
3. The wheels of sports cars, from Formula 1 to circuit racing, are only pumped with nitrogen. For fans of high speeds, we recommend following the example of professional racers.
4. Pressure stability is also important for the tires themselves, which, with changes in temperature and pressure, wear with greater intensity. By inflating tires with nitrogen, you will significantly extend their service life.

So, the savings are obvious - tires last longer, never burst or explode. By the way, practical foreigners have been pumping tires with nitrogen for many years. At every gas station or car service, along with a conventional compressor, there is a nitrogen compressor. Service workers will learn to pump the wheels with nitrogen over the colored valve caps. When purchasing a car driven from abroad, pay attention to this.

Now let's take a closer look at all the advantages of pumping tires with nitrogen., but to begin with, let's refresh our memory of a course in physics of a general education school, and for many tire fitters this may become just a discovery and will turn the whole idea of ​​pumping tires and not only nitrogen. And those diligent students who did not smoke a physics textbook earlier and made it to the 9th grade could learn the following in their lessons:

The law of proportional dependence of the volume of gas on the absolute temperature at constant pressure, named after the French physicist and chemist Joseph Louis Gay-Lussac, who first published it in 1802.

In the Russian and English-language scientific literature, there are some differences in the naming of the laws associated with the name of Gay Lussac. These differences are summarized in the following table.

Whoever retained the priority of this discovery, Gay-Lussac was the first to demonstrate that the law applies to all gases ... (ATTENTION! We repeat once again: THE LAW APPLIES TO ALL GASES, and not nitrogen or oxygen or any other gas separately). Mathematically, he expressed his discovery as follows:

where V- gas volume, T- temperature.

Now let's try to analyze all the miraculous properties of nitrogen injected into the tires separately:

Misconception # 1. Improving the stability of the tire pressure. The thermal expansion coefficient of nitrogen is much lower than that of air, and therefore, when the tire heats up, the pressure practically does not change.

- This statement contradicts the laws of physics, namely Charles's law (gas pressure in a constant volume is directly proportional to temperature) and Gay-Lussac's law (the coefficient of volumetric expansion of all gases is the same), which we passed in the 9th grade of a comprehensive school.

Physicists can be trusted, which means that "service sellers" cannot be trusted.

Misconception # 2. You can check the tire pressure three times less often. Due to the fact that there are more nitrogen molecules than oxygen molecules, the wheel is lowered more slowly.

- nitrogen molecule 3.1x10 ^ -8cm, and oxygen molecule 2.9x10 ^ -8cm. Those. an oxygen molecule is 6% smaller than a nitrogen molecule. And given that there is only about 21% oxygen in the air around us, and the remaining 78% nitrogen, it turns out that the difference in leakage is very insignificant (about one percent).
And nevertheless, if we still assume that oxygen leaks out of the tire faster than nitrogen. So if all the oxygen flows out of the tire on its own, there will be only nitrogen left there? I pump it up with air (in which, as always, 78% nitrogen) and the tire will have 94% nitrogen. The second time I pump up - it will be 98%, and from the third run - the tire is almost completely filled with nitrogen. It turns out that we are already skating on pure nitrogen. Or are they confusing something?
In fact, modern ones (if they are in good working order) hold pressure for years. And if there is a problem in the bus, i.e. it is leaking, it does not matter whether the nitrogen is injected into the tire or with oxygen impurities - the tire will still deflate.
In addition, clause # 2 contradicts - clause 70 - Check the internal pressure in cooled tires with a manual pressure gauge at least once a week.

Misconception # 3.Reducing the likelihood of tire explosion. Nitrogen is an inert gas and does not support combustion.

- the tire does not "explode" as we imagine it, but bursts. The balloon also bursts regardless of whether it was pumped up with air or helium. Those. the sound we hear is a sudden loss of pressure in the tire, which is usually caused by a collision of the car with a foreign object or destruction of the structure of the tire itself.
In Formula 1, nitrogen is pumped into tires primarily for fire safety. Pure nitrogen, if the wheel is damaged, coming out of the tire really does not contribute to combustion.

Misconception # 4. Prevents tire aging and rim corrosion because there is no moisture, oil, dust, particles that reduce the durability of the wheel.

- tire aging mainly occurs outside the tire, because in addition to oxygen, solar radiation and other harmful influences (reagents, bitumen, etc.) act on the tire, and there is no way to get rid of this aging, because they have not yet come up with special tire covers, then the tires would not be tires, but products in cases.
Corrosion of the disc from the inside is really reduced due to the lower amount of oxygen in the tire, but mainly due to the absence of moisture in the air, it should be removed from the air mixture by a little decent compressors at any tire service. But it is worth noting that the disc again mostly rusts and oxidizes on the outside, although some of the benefits of using nitrogen in this case are present.

Fallacy # 5. Reducing noise and vibration from the contact of the tire with the road surface, increasing the smoothness and softness of the passage of irregularities in the road surface, improving the grip of the tire with the road surface and reducing the braking distance.

And no matter what miraculous properties nitrogen has, it cannot affect the noise of the tire and the grip - he cannot change the tread pattern!

Fallacy # 6. Reducing the load on the car's suspension, improving wheel shock absorption.

The reduction in unsprung weight "will be noticeable in terms of vehicle dynamics and fuel consumption." Imagine how many tenths of a gram the 15-kilogram wheel will become lighter! How not to notice the fuel consumption! Probably two grams a year can be saved. And who's lucky - all three!

There are other dubious statements, many of which contradict the laws of physics, but there is little point in commenting on them.
So let's summarize: most of the theses that are advertised are not valid. And some are just outright deception.
Although there is also a psychological factor - people who spent their money and pumped up tires with nitrogen often say: "They pumped nitrogen into my tires - and the car began to drive smoother." Softer, softer, softer ... A person gets into a car, and it seems to him that the suspension really behaves softer. But remember how the car suddenly gets faster and sportier when you drive in high spirits. And how the engine barely pulls when you're out of sorts ... In addition, they get colored caps on the wheels. The most surprising thing in this story is that many motorists have taken the side of the "gas workers". They sincerely assure that the car has indeed become softer. But it is not physicists or automotive technicians who should understand this phenomenon, but rather psychologists. People are prone to suggestion, often turning into self-suggestion.
And if you want to check the laws of physics at your own expense, then please, there is such a service. But still, there is one really positive point in this procedure, and this can be said for sure - it will not get any worse!

Just attention! Some savvy tire changers have long realized that, in fact, there is no use from tires filled with nitrogen. Curious motorists have already seen "master innovators" pumping ordinary air under the guise of supergas. The cunning set up a pumping stand in such a way that the hose with the gas "mixture" goes somewhere inside the tire building. If you carefully trace where it ends, it turns out that the hose is connected to a pipe coming from a compressor that pumps ... ordinary air. I think it's very funny to look at people who buy air from you at the price of nitrogen ...
Be carefull! Check the pressure in the "cold" tires with your pressure gauge (for example, in the morning, before driving). Because often, to obtain a "soft effect", tire changers inflate tires with nitrogen (or just air) at a reduced pressure. This can lead to tire puncture and wheel damage, especially at high speeds.

What for? Filling tires with an air mixture has a number of disadvantages, which can be avoided using the modern method of inflating tires with nitrogen:

1. The air mixture causes oxidation processes inside the tire. Oxygen and moisture contained in the air mixture destroy the inner hermetic layer of the tire and provoke corrosion of the steel cord. Nitrogen contains no oxygen and moisture impurities that cause corrosion.
2. The pressure inside a tire is unstable when it is inflated with an air mixture, as oxygen expands when heated by movement. Driving on tires with the wrong pressure leads to increased tire wear, reduced vehicle stability, reduced braking and adhesion properties of tires, ride comfort (the car reacts more sharply to unevenness), and overall road safety. The thermal expansion coefficient of nitrogen is lower than that of oxygen and avoids the dependence of pressure on temperature.
3. The need for swap. The nitrogen molecule is larger than the oxygen molecule, due to this, nitrogen seeps through the rubber micropores more slowly, pumping is required 40% less often.

To summarize, Benefits of Using Nitrogen to Inflate Tires are as follows:

• Increased tire life - preventing premature aging, tire depressurization and rim corrosion;
• Reducing the likelihood of tire damage as a result of improper pressure in it;
• Stability of tire pressure, frequent checks and inflation are not required;
• Fuel consumption is reduced, the correct pressure ensures low rolling resistance.

Thanks to these factors, not only the efficiency of the tire is increased, but also the safety of its operation. Thus, increased safety is the main advantage, which ensures the inflation of tires with nitrogen.

How is it going? The process includes the following steps:

1. Compressed air is pumped into the working system of the nitrogen generator for processing, at least eight atmospheres.
2. Multilevel filtration is carried out, during which moisture, impurities and oils are removed from the air.
3. The purified air is passed through membranes separating only nitrogen -n2 molecules. The result is nitrogen with a purity of more than 95%.
4. Nitrogen supply to the inner cavity of the tire by means of a compressor.

Why MBO? Using the service of filling tires with nitrogen in the Trade and Service Centers of the Moscow Military District, you can be sure that we use high-class equipment and the quality of the work performed. Tires are pumped with nitrogen in the MVO Trade and Service Centers using professional equipment Nitro Ride (Great Britain), which allows you to get and pump nitrogen into tires with a purity of up to 99.9%, without moisture and other impurities.

Providing the service of inflating tires with nitrogen, we take care of your safety and your car.

The idea came from motorsport: the tires of Formula 1 cars are really pumped with nitrogen. Typically, in the event of a car fire accident, a burst tire will pressurize oxygen, much like pumping air into a forge to raise the temperature. But tires inflated with nitrogen do not add fuel to the fire under the same conditions.

But that's in sports. And "in civilian life" we see fires in case of car accidents much less often. In the end, the designers did a lot of work to reduce the fire hazard in an accident.

The price of the issue

Arriving at the tire service and yielding to the persuasion to refuel the tires with nitrogen, you will see that air is first pumped out of the tires of your car, and then they are filled with nitrogen from a special installation. will be installed according to the technical requirements of the vehicle manufacturer. This procedure will cost from 180 to 260 rubles per wheel. The larger the diameter, the more expensive.

Advertising move

At a branded expensive tire fitting, almost any car owner, and especially the owner, will probably be offered. There are a lot of arguments in favor of this procedure. Let us analyze which of them are true and which are fiction:

1. The tire pressure will be stable because the nitrogen hardly expands from heat. But there is already 78% nitrogen in the air, so the changes are accounted for by the rest of the gases, which also do not expand beyond measure. The difference in the coefficient of volumetric expansion is negligible with a significant digit in the fourth decimal place.
2. Nitrogen molecules are larger and therefore not so quickly penetrate the tire walls to the outside, keeping the pressure stable. But do not forget that there is not so much oxygen with other gases - about 22%. And when they begin to evaporate, and we start pumping up the tire, the nitrogen concentration will increase. So, a 5-6-year-old wheel forms an almost purely nitrogen "atmosphere" inside.
3. A wheel filled with nitrogen is lighter than a wheel filled with atmospheric air. This allows . Simple calculations show that the wheel of a midsize crossover will only get a few grams lighter. And how much do the stones stuck in the tread weigh? Let's better clean the tread more often, especially since the tire design engineers highly recommend it.
4. The lack of oxygen protects the tire material from premature aging. The tire workers support this thesis, but you do not hope that after a century your tires will be located on a pedestal, like the wheels of Lenin's armored car. The wear and aging of the outer layers of rubber under the influence of the sun, ozone, and moisture occurs much faster.
5. Better grip and greater safety due to performance stability. I disagree: it is still necessary to check the tire pressure periodically, and with each "zigzag" precious nitrogen will come out. And after all, you cannot disappoint. So the servicemen strive to tie the car enthusiast to their workshop, even for such an insignificant problem as checking the pressure and pumping the wheel.

Real alternative

It is difficult to save money on "nitrogenous" tires, but there are more effective methods. Moreover, both free and very expensive:

• Timely seasonal tire change that meets both legal requirements and common sense. Summer tires are definitely easier to roll!
• Before long journeys on the highway at 0.2 bar. It will be a little tougher, but significantly more economical.

• Use lightweight wheels, and not any light-alloy wheels, but preferably forged ones, they often have a noticeably less weight. And in general, not by design, but by weight. But for the relief without sacrificing durability, look for certified rims.

• Use tires made using Energy saver technology. Many manufacturers have these today. They have a slightly lower rolling resistance due to the use of technologies that are sharpened specifically for resource saving.
• Select tires using the results where rolling resistance is measured for each applicant.
• Install light-alloy (and really light) wheels with a larger diameter and use the tire calculator to select the appropriate tires, while maintaining the outer diameter of the old wheel. Well, or a little more.
• You drive a lot on the highway, but with little load, or the gears in the box of your car can be called “short”, as, for example, in Renault Logan or Lada Largus. That is, at 100 km / h, the engine makes more than 3000 rpm in top gear. Then slightly larger tires can be fitted. This will make all gears slightly longer and will save fuel.

At some tire shops, drivers are offered a service of filling tires with nitrogen instead of regular air, since it has many useful properties, which will make the operation of the vehicle easier, more comfortable and safer. Of course, this service costs significantly more than a simple pumping of the wheels from the compressor, however, following the trends of the time, many motorists agree to this service and leave the service station with cylinders full of this volatile gas.

Nitrogen inflation is a worldwide trend of filling tires with a nitrogen / air mixture instead of regular air. This method originated in Formula 1 races, when to increase the efficiency of the car, its tires were filled exclusively with this mixture, and the pilots really noted it as one of the advantages for the desired victory.

Tire inflation with nitrogen

Further, this method was adopted for ordinary cars by tire fitters from the United States several decades ago. And more recently he came to our country, many craftsmen willingly offer this service to their customers during vehicle maintenance.

Why are the wheels pumped with nitrogen and how does this affect the operation of the vehicle? According to the assurances of numerous experts around the world, this service has the following advantages over filling cylinders with ordinary air:

• The physical properties of nitrogen do not change its volume under the influence of temperature differences, the pressure in the tire, regardless of the season, remains unchanged, which allows maintaining the same speed and fuel consumption.
• Nitrogen molecules are somewhat larger than air and also less volatile. This leads to the fact that the wheel needs to be pumped up much less often in the absence of holes or defects in the nipple.
• Due to the fact that oxygen is an oxidizing agent, it gradually corrodes the rubber from the inside, and nitrogen does not have this property, which is why the wheels pumped with this gas will last much longer, especially when the driver drives carefully.
• Nitrogen is less dense than air mixture, which makes the tires weigh less, and this is especially important in rally competitions, where thousandths of a second matter.
• During a long ride at high speed, the wheel is heated, but when nitrogen is pumped in, heat removal will be many times more efficient, and the likelihood of overheating the rubber is much lower.
• Nitrogen can never ignite or sustain combustion, so there is less chance of an explosion in a car fire.

Formula 1 tire inflation

Skeptics believe that many of the above properties of nitrogen are grossly exaggerated, and in reality things are completely different. However, this is not the case, and the effect of each of these properties takes place, albeit on a very small, sometimes invisible scale.

Negative aspects of pumping wheels with nitrogen

There are pros and cons to pumping tires with nitrogen. What should a driver who is offered this service at a service station do? Of course, this method cannot be limited only by the positive aspects, and in the end it is not as effective as it might seem from the words of the consultants. So, the main disadvantages of pumping wheels with nitrogen, which are a reality of life and based on scientific facts and long-term practice of driving a car by professionals, are listed in the following list:

• The cost of the procedure, since when the wheels are pumped with an air mixture, it is pumped by the compressor directly from the atmosphere, which reduces the cost of the service to almost zero.

As for nitrogen, it is practically impossible to extract it in domestic conditions directly from the surrounding air, despite the fact that it prevails in the chemical composition of the earth's atmosphere. Thus, it is produced in laboratory conditions, filled with cylinders and delivered to the place of sale at the request of the seller.

All these procedures are very expensive, and given the commercial interest of the craftsmen at the service station, a rather high price falls on the client's pocket for a simple pumping of wheels, and this often repels motorists.

• The second important problem is that with a leaky nipple or some other reason for a loss of pressure in the wheel, it is, of course, possible to pump it up right on the road with a portable car compressor. But all the positive effects of nitrogen inside the wheel will be immediately lost.

To prevent this from happening, the compressor must have a special adapter to be able to switch the source of the gas intake from the atmosphere to a nitrogen cylinder, and it must also be in the arsenal of a motorist.

Composition of atmospheric air

It is almost impossible for a driver who decides to fill their wheels with nitrogen to avoid such disadvantages. He will only have to accept and more carefully control the risk of gas leakage from his tire, checking the serviceability of the nipples on each wheel, as well as the integrity of the rubber.

Myths and reality of nitrogen pumping

Every car enthusiast who knows this method of tire inflation has a certain opinion on this matter, and it does not always coincide with the facts advertised by consultants in service centers. So, numerous reviews of drivers about the use of nitrogen in the tires of their own cars speak of the following facts and myths:

• Why are the wheels pumped with nitrogen and how effective is it? There is an opinion that the driver, when driving on tires, pressurized with nitrogen, will experience more comfort than the one who uses regular air. Yes, indeed, the same pressure created by nitrogen will somewhat soften the depreciation of the vehicle, but this factor is almost invisible. If the driver sets the air pressure inside the wheel not to 2.2 atm., As it is written on the threshold of the driver's seat, but to 0.05 atm. less, then the effect will be absolutely comparable.

Bursting a tire inflated with nitrogen

• Experts also say that nitrogen makes the car a lot lighter - yes, it does. But the difference in the density of air in the lower layers of the atmosphere is only 7% different from the same indicator for pure nitrogen, as a result of which, even for 50 liters of air on all wheels of a car, the difference in mass will be hundredths of one gram, and for a car weighing 1.2 tons it is minuscule.
• Formula 1 cars are pumped with nitrogen because of the incombustibility of this gas, as it is believed to be safer to drive. However, as a rule, a rider is killed or injured not from a fire in tires, but from loss of control due to tire rupture, and this can happen both with air mixtures and with nitrogen inside the wheel.
• The fact that inflating is less frequent is also debatable, since a high-quality tire, a serviceable nipple and a quiet, neat ride contribute to keeping the air inside the tire, and it should be inflated no more than once every 3 months. In the case of nitrogen, this indicator can stretch up to 3.5-4 months, which does not compensate for the overpayment for this fashionable way of pumping pressure into the wheel.

Checking tire pressure

• On the subject of longer aging of tires, the fact is subject to refutation almost immediately. The fact is that a wheel at rest can undergo air oxidation for several decades. However, those people who pump nitrogen into their tires tend to operate the vehicle frequently by subjecting the tires to friction from the outside against the roadway.

Thus, no matter how carefully the vehicle is operated, wear always begins from the outside - when the protectors come into contact with asphalt or other rubber elements with an aggressive environment. It is this part that will deteriorate much faster than the inner layer of the tire.

Based on the factors listed above, only one completely reliable fact can be cited - refueling tires with nitrogen to some extent affects those fractions of a second that racers at professional rallies sometimes really need, but this is 100% the lot of professionals only.

The same individuals who are trying to present these highly specialized methods of forcing pressure into the life of an ordinary car enthusiast simply conduct commercial activities and try to give the most effective advertising campaign.

Nitrogen cylinders for tire fitting

We can say with full confidence that an ordinary driver who operates his car on city roads or suburban roads, without setting himself any competitive goals, does not need this service at all. They can always get by with practically free pumping of the wheels with atmospheric air, which can be done in any conditions - both at a tire shop and just on the road with a small household compressor.

At the same time, the level of safety of the driver and passengers on the road while driving does not depend in any way on how to pump up the wheels - nitrogen or air.

Why did this topic turn out to be so tenacious at all? On the one hand, "it is obvious to any adequate person" that this is a divorce - they joked and forgot. But on the other hand, there is motorsport. Where a car is built by dozens of engineers who know everything about physics. And where "the wheels are pumped with nitrogen."

The man laid out the essence well. He even remembers the laws of Charles and Gay-Lussac. And he concludes: “In Formula 1, nitrogen is pumped into tires ONLY! for fire safety. Pure nitrogen, if the wheel is damaged, coming out of the tire really does not contribute to combustion. "... This statement is incorrect.

Now to the point. In motorsport, the wheels are really pumped with nitrogen. I'll tell you why.

Firstly, it is not always nitrogen, it can be a mixture of similar gases or simply dry air. Specifically, in Formula 1, it is now forbidden by the regulations to pump something other than air, so they pump air - the key word - dried. (By the way, as you can see, the danger of fires :) did not prevent this point from being included in the regulations.)

A simple Google search finds us interviewed by Paul Hembri, CEO of Pirelli Motorsport, with the answer to this question.

- What gas do you use to inflate tires?
- Previously, the use of special gases was allowed, but now it is prohibited and we inflate the tires with dry air - the moisture is removed to ensure the necessary stability.

But from the link above, we read:
Statement 1. Improving the stability of the tire pressure.
- This statement contradicts the laws of physics, namely Charles's law (gas pressure in a constant volume is directly proportional to temperature) and Gay-Lussac's law (the coefficient of volumetric expansion of all gases is the same), which we passed in the 9th grade of a comprehensive school.

Wasn't the head of Pirelli Motorsport in ninth grade? Paul Hembri, Charles with Gay-Lussac, and a respected Dviv citizen - I suggest you make a bet right now, which of them "is not catching up with something." :)

In fact, everything is simple. The essence of the problem is the moisture contained in the gas.

Indeed, "the gas pressure in a constant volume is directly proportional to the temperature" (Charles's law itself sounds like P (gas pressure) / T (temperature) = const and is true for an ideal gas, which, with a very high degree of accuracy, is also air with nitrogen in the tire) ... That is, in this case, the higher the temperature inside the tire, the higher the pressure. Therefore, when the car starts to move and its wheels start to heat up, the pressure in the tires increases. Two-four-tenths of the atmosphere, even a tire already warmed up before the start, gains easily. Nitrogen is absolutely no exception to this law - even if you pump up the wheels with nitrogen, the tire will pick up the same two to four tens of pressure as in “normal air”.

There is no need to explain how important tire pressure is for a race car. Moreover, it is the pressure “on the hot” that is important. What is the pressure in a cold wheel - it does not matter, it should be correct, when the wheel starts running, it heats up and starts working. And the essence of the problem is that if humid air is pumped into the wheels, then when the wheel cools and heats up, the amount of gas in the tire will start to change arbitrarily - and the pressure will start to jump arbitrarily.

In practice, it looks very simple - before the start (during collection), the same pressure is set in the wheels of the car, say, 2.0 atm. The car drives several laps (or - in the rally - additional), the pressure is measured, and it turns out that the pressure in one wheel is 2.2, in the other - 2.4. (At this point, the mechanics who assembled the wheels are given the brains - the procedure for collecting the wheels has been violated.)

Why it happens? There is such a thing - dew point. This is the temperature to which the air must be cooled in order for the water vapor contained in it to reach saturation and begin to condense. The dew point is determined by the relative humidity of the air - the higher the relative humidity, the higher the dew point and closer to the actual air temperature. If the relative humidity is 100%, then the dew point is the same as the actual temperature.

That is, 100% air humidity means that there can be no more water vapor in a given volume of gas - then it will begin to condense. When we pump such air into the tire, that is, we raise its pressure, and then let the wheel cool down, then water vapor condenses inside the tire into water droplets. Checking the pressure in such a wheel, we will see, for example, 2 atmospheres. When the car starts to move and the wheel starts to heat up, some of these water droplets will begin to evaporate, adding additional gas to the tire. The added amount of gas will add pressure (see "partial pressure" - the total pressure of the gas mixture is the sum of the partial pressures of its components). It is impossible to predict how much water will evaporate (how much of it got into the wheel during inflation?), So the pressure will cease to linearly depend on temperature. And when the car starts moving, there may be 2.2 atm and 2.4 atm.

For a race car, this pressure difference is dramatic.

Therefore, in big sport, wheels are assembled according to a certain procedure. And indeed, many people pump it with nitrogen. Other teams use compressors that dry the air.

In a time attack, where more than half of the participants do not have their own team of mechanics, and the wheels are assembled and pumped up with a regular pump, often even without a dryer (or with a simple one), you just have to check the pressure after each session and, accordingly, deflate / inflate the tires, setting the optimal pressure until it "settles" at the desired level. If "civilian" tire fitting provides the service of "pumping tires with nitrogen", then it should also be used "carefully". In order to pump up the wheel with nitrogen, you first need to blow it off. When the gas is blown off, that is, the pressure decreases, it cools, which can also lead to condensation of some of the moisture inside the tire. Therefore, in big sports, to minimize the presence of moisture inside the wheel, it is left "open" for several hours, then pumped with dry air (nitrogen) and left for several hours, again to equalize the temperature, and then the final pressure is set. With this procedure, you can already count on the fact that when driving, the pressure in the wheel will increase linearly, in direct proportion to the temperature, and this increase can be predicted.

Well, in conclusion - does all this have to do with a civilian car? Virtually none. The tires of a civilian vehicle hardly get warm while driving. (By the way, many people think that the tires get hotter from friction on the road, but in fact they first of all heat up from the brakes through the discs, friction on the road is already the second factor even for a racing car, and for a civilian wheel the second most important factor - internal friction in the tire, which arises from deformation during the rolling of the wheel).

The only case when the temperature changes perceptibly, and, accordingly, the pressure in the civilian wheel is if you inflated the wheel in the spring at +5 and did not check the pressure until the summer, when it became + 30 ... and even left the wheels in the direct sun. Then, indeed, some kind of pressure spread can turn out in the wheels (although it will not be critical for civilian driving anyway). But it's easier to just check the tire pressure once a week than to bother with nitrogen or dehumidification.