# Until what time do you need to swing the wheels on the bike?

## A short course on wheel pressure or the answer to the question: “how many atmospheres to pump bmx wheels?

All of us, when we just bought the first bmx, wondered this question. Someone pumped more, someone less, and someone did not have a monometer and pumped to the touch. And after a huge number of punctured cameras, a huge number of different patches and boxes of glue, a popular answer arose: “3-4 atmospheres in the front wheel, from 4.5 atmospheres in the rear”.

Motorists twist their fingers at their temples, and tire changers with round eyes ask: “won’t it explode?”

But let’s figure out why it is so and what should really be.

The answer is this: at low pressure in the wheel, during an impact or landing, the tire flexes and the tube is simply “pressed” against the rim walls. Since the chamber itself is thin, it turns out that the walls of the rim simply cut through the chamber. As a result, we find in the deflated chamber two small holes at the same distance from each other (the so-called “snake bite”), and we can also see dents on the walls of the rim.

As a more striking example, let’s imagine that on the blunt side of the knife we ​​put oil from the refrigerator, in briquettes which. We put the board on top and then hit it. As a result, the oil will be cut. But if you first freeze the butter in the freezer, then the knife will reach the middle as much as possible. Here everything will depend on the oil, the width of the knife and the force of the blow. Essentially the same as in the wheel.

If we take it from the origins, then most of our parents, grandmothers, grandfathers and so on for some reason had the opinion that it is necessary to pump up the wheels in a bicycle so that the tire sags a little with your fingers. And if you pump more, then the wheel will explode. But for some reason, no one thought about the fact that the strength in the fingers is different for everyone, and on the side of the tire it is written how much pressure should be pumped.

So we came to the first answer to the question “how many atmospheres to pump into the wheels on bmx?”:

Many tires have minimum and maximum pressures indicated. But there are exceptions here too. On some tires, the maximum pressure is quite low, and looking at the minimum indicated pressure, it seems that the tire is designed for a 5 year old child. I would also like to note that there are such tires, the manufacturers of which immediately warn that when pumping less than the minimum pressure, the tire begins to wear out and deform quickly (for example, ultra light tires of the KHE Mac series).

At this moment, many will think: “Yes, I’ll pump it up to the maximum and everything will be fine.” Stop, go to the kitchen, put the kettle on to boil and read on 🙂

If you are a beginner and still don’t understand what tires there are, or you are already experienced, but at the same time you have tires of the “lousy” class, then it is better not to greedily pump to the maximum right away.

• The most common thing that happens. the tire simply explodes and as a result, you are in a state of stunning trying to figure out where to get money for a new tire, a camera and a hearing aid.
• At high pressure, the wheels become “stone”, which means that they absorb less shock and do not dampen vibration. As a result, after landing, especially on the front wheel, you freak out from wild pain in your wrists, and while driving, especially on the broken Soviet tiles, not only your wrists, but also your knees and possibly even teeth begin to freak out from vibration.

By the way, from the point of view of medicine, prolonged vibration is considered more destructive than the impact of landing.

Conclusion on high pressure. while you are a beginner, do not pump up the wheels too much, let your joints get used to the loads.

And after so many letters we have read, we are left with the thought: “you can’t pump a little, it’s too early to download a lot”.

And here we come to the most popular answer: “3-4 atmospheres forward, from 4.5 atmospheres backward”.

In addition, I would like to note the following:

• The article is designed for Street riding. If you decide to ride Dirt, then the pressure there can be slightly reduced for better traction and a softer landing.
• Much depends on your goals. Some riders lower the rear wheel for better manual control, while those who like to jump on the footjam lower the front wheel to spring.
• Never ask how many atmospheres are pumped by those who ride Flatland. And if it’s a secret, then they have a pressure in the wheels of 7 and higher. They do this so that the tire does not sag under their weight, thereby increasing roll and simplifying rotation and balance.

And finally. Thanks for reading and go for a drive don’t break through ^ _ ^

### Bicycle tire pressure in extreme summer heat

If the temperature is high outside, it is better to reduce the pressure a little. Remember that the wheel can overheat. The hot asphalt itself and the friction of the tires on it heat the chamber and the air inside it, which accordingly increases the pressure. So, a tire inflated to its maximum value in hot summer can suddenly explode.

In more detail the question of the influence of air temperature on tire pressure is described in a separate article “Dependence of tire pressure on temperature”. Calculation formulas are also given there.

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Here, for example, we give a table for determining the pressure in a bicycle wheel from the air temperature, if it is inflated at a temperature of 20 ° C.

## What pressure should be in bicycle tires (how many atmospheres)

In this article, we will answer the question that many cyclists are asking: How much pressure should the tires of a bicycle be? We note right away that tire pressure is the most important factor that affects the flotation and roll rate of your bike. That is why the pressure in the wheels must be correct.

The required pressure will help you determine the allowable values ​​on the tires. All products, regardless of the manufacturer, must indicate the minimum and maximum allowable pressure. In rare cases, only one value is indicated. the maximum. Also, these values ​​can be specified in different units of measurement: P.S.I pressure in pounds (American designation) or BAR. pressure in bars or atmospheres. In the table below, we have compared all possible values ​​with a person’s weight so that you can easily determine the required pressure based on your weight.

A floor or hand pump with a pressure gauge will help you to correctly determine the pressure in the wheels. Be careful when using compressor pumps, as they deliver a large amount of air at a high speed, which can lead to an explosion of the chamber.

### How is blood pressure measured?

It is customary to designate pressure in three units of measurement:

• Psi. pound-force per square inch. pound-force per square inch;
• BAR. bars, usually equated to measurement in “atmospheres”;
• Pa. pascal.

Since many tire manufacturers focus on the American market, the Psi designation is most often found. In English-speaking sources, it is usually simplified to “pound”, or pound, that is, when they say that a pressure of 2 pounds, they mean Psi. This unit of measurement is outdated, used only in the United States, but, as they say, “more alive than all living things”.

Bars are also obsolete units of measurement, but are actively supported in Russia and many other countries, incl. European. This unit of measurement is actively used, as it has something in common with the “atmosphere”, which is quite convenient for measurements.

Pascal is the only metrically correct unit on the list, but rarely used in bicycle designations.

The ratio between all units is as follows: 1 Bar = 100,000 Pa = 14.504 Psi.

### High lug tires

All toothed tires designed for travel on soft ground, sand, snow are best used with high pressure. In this case, the adhesion will be maximum.

## What to pump up

Bicycle luggage requires maintenance and pumping very often. Even on the most “hardy” city and mountain bikes, it is required to check and pump up the camera every 2-3 weeks, since the air leaks not only through the nipple, but also simply through the rubber. High pressure “helps” air molecules find their way through an insufficiently dense chamber.

### Bicycle Wheel Balancing: Marginal Gains or a ‘Must Do’?

“City”, or, simply, budget bicycles, it is enough to pump up once every 2-4 weeks, mountain bikes. at least once every two weeks, road bikes. once a week, and road and sports bikes. before each trip.

Therefore, the pump is not only an emergency accessory that is used only when a punctured wheel is changed, but also a necessary part of the preparation for departure. Active cyclists should consider purchasing two pumps:

• portable. as part of an emergency kit or on long trips;
• stationary with a stop and a pressure gauge. for periodic maintenance of your tires.

By the way, an ordinary car pump perfectly takes the place of a stationary pump. It is also suitable for bicycles, shows, shows exactly how many atmospheres are pumped up, and does not take up additional space. Some people prefer to pump up on “professional” pumps at gas stations, but the lack of their professional tool can play a bad joke in the event of an unexpected situation or when you deviate from the standard route.

## What is written on the tires

The secret to making the right choice is very simple: just look at the inflated wheel. Next to the information about the size of the tire, there will also be information about the permissible pressure range in the chamber.

Why is this information not shown on the camera itself? Because in it the only point subject to real stress is the nipple, and its mechanism is very reliable. Otherwise, the normal pressure, which increases by an order of magnitude during fast skiing, is taken by the tire, and how much it will be compressed is the main limitation.

So, if the pressure is too low, the tire will break closer to the rim, bite the chamber, leading to a breakdown, and if it is too low, it may just burst on one of the bumps or when driving on hot asphalt.

### Here it is necessary to clarify a little what BAR, PSI and kPa are.

• BAR is the pressure in bars or atmospheres. For our people, the most understandable designation. It is used in many countries, including the post-Soviet space. 1 BAR = 1 atmosphere
• When the pressure in BAR is multiplied by 100, the result is kilopascals. In this case, it will be 250 and 420 kilopascals. Pascals are designated by English letters “Pa” or if in “kilo”. then kPa. They sometimes do the same, indicate the minimum and maximum pressure for which the tire is designed.
• PSI (pound-force per square inch). pressure in pounds per square inch. Used in Europe and some American states. It is designated as PSI or LBS / IN 2. For the given example, these are 36 and 60, respectively.

The relationship between BAR, PSI and Pa is as follows:

1 Bar = 1 atmosphere = 100,000 Pa (100 kPa) = 14.504 Psi,

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With Bar and Pascals everything is simple, but with the translation of Bar to PSI, everything is a little more complicated, so here is a table for quickly converting pressure in bicycle tires from Bar to PSI and vice versa:

Let us mention one more designation for pressure, which is called “kilogram of force per square centimeter” or “technical atmosphere” and is denoted as “kgf / cm²” or “kgf / cm²”. It is quite rare, but it happens. We will dwell on the technical nuances, there are a lot of articles on this topic on the Internet, let’s just say that for a bicycle pressure it can be considered equal to 1 Bar or one atmosphere.

And for lovers of exact mathematics, here are the conversion factors:

1 kgf / cm² = 1 atmosphere = 0.98 Bar = 98.07 kPa = 14.22 PSI

When pumping up a tire, you need to clearly understand that the pressure in it should not be lower than the minimum specified and higher than the maximum. It is worth noting here that it is better to leave a small margin of 0.2-0.5 atmospheres, without pumping the tire to the maximum value so that it does not burst, especially in hot weather.

About what else the manufacturer writes on bicycle tires, as well as what other numbers mean, there is a separate article on it on our website, which is called “What do the numbers on bicycle tires mean”.

## What pressure should be in bicycle tires

When buying a bicycle for themselves, many will not even think about the fact that the convenience and comfort while riding it is achieved by correctly selected tire pressure. How inflated the wheels affect the life of the bike, the riding speed, the degree of tire wear, safety, control of the control of the two-wheeled friend.

## Bike type

The nature, riding style and type of bike also affect the level of tire pressure. Active shoppers often opt for 26-inch mountain bikes that ride well on city streets and off-road.

To understand the pressure to inflate the wheels of a bicycle, it is necessary to take into account the peculiarities of both the bike itself and other, at first glance, weightless factors. For example, tire weaving, rim thickness, driving style. The likelihood of a tire falling off a wide rim is much less than from a narrow one, because a wider rim will hold the tire better than a thin one. A mountain bike, by its very name, suggests the presence of a difficult surface on the track, with possible obstacles and irregularities. Driving style is more aggressive than on a flat, calm trajectory, obliges to increase the tire pressure to a level slightly less than the upper limit.

The diameter of the wheel will also affect the selection of the optimal pressure value, since the larger it is, the higher the volume of pumped air will be. However, for mountain bikes, 26 or 29 inches of wheel diameter is not so important, much more attention should be paid to the parameters of the cyclist’s weight and the type of track.

## Air temperature

Many cyclists do not think about the fact that the air temperature affects the pressure level in the tires of the bicycle. From the course of school physics, we recall that when heated, bodies expand. This means that in hot sunny weather, the pressure inside the air chamber will increase without additional pumping. Conversely, on cold winter days, a drop in tire pressure due to low temperatures is quickly felt. This means that when going on a bike ride in the cold season, the pressure indicators need to be adjusted slightly higher than usual, and in the summer heat, bleed the air a little. It is worth noting that when going on bike rides, you always need to take into account the weather conditions.

## Tire type and rubber surface

The type of tires is determined by the surface of the track, on which the cyclist will mainly ride. Accordingly, the inflation rate of the bicycle wheel will be different. There is a direct dependence on the roughness of the tread and the width of the wheel. the more lugs and the wider the wheel, the lower the pressure should be. Experienced cyclists quickly determine how much atmosphere should be in their bicycle tires.

## Cyclist weight

It is important to consider the load on the bike from the rider’s own weight, especially the fact that most of it comes from the rear wheel. Therefore, the degree of its pumping should be slightly higher than the front, the optimal difference is 10%.

To calculate what the optimal pressure should be in the tires of a bicycle, taking into account the weight of its rider, you can use the table:

Cyclist weight (kg) Pressure (atmospheres) Pressure (PSI)

 50-60 2.4. 2.9 34.81. 42.06 60-70 2.9. 3.2 42.06. 46.41 70-85 3.2. 3.7 46.41. 53.66 85-100 3.7. 4.0 53.66. 58.02 100-120 4.0. 4. 58.02. 59.47

Tire inflation will directly depend on the rider’s weight. The larger it is, the more atmospheres need to be pumped into the bicycle wheel. However, you should always remember that overloading the bike with simultaneous pumping of the wheels can lead to a twisting of the rim into a figure eight or a tire rupture.

### Weight changes

For heavy riders or heavily loaded bikes, it is very important to add pressure, as a lot of mass will squeeze the wheel of the bike and problems with insufficiently inflated cameras can come out much earlier.

Recommended pressure for weight addition is 1% for every kilogram of rider weight over 50.

## How many atmospheres in the wheel is considered normal?

Each vehicle has a specific tire pressure rating. As a rule, this norm is indicated on a sticker inside the driver’s door, but if it is not there, you can find the functions in the owner’s manual (in the manual). It is very important to observe exactly this number of atmospheres, because the correct tire pressure is very important to reduce gas consumption and prolong the life of your tires.

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So how many atmospheres per wheel is recommended? Most passenger cars will recommend 32 to 35 psi (2.21-2.41 bar) in the tire when cold. Why exactly cold? Because the tires roll on the road and the friction between them and the road generates heat, increasing the tire pressure. Do not pump your wheels to the pressure indicated on the tire itself. The maximum number of atmospheres is indicated there, and not a recommendation.

Sometimes drivers do not use the recommendations and adhere to the general rules. pump up pressure on the front wheels. 2.2 atmospheres, while on the rear wheels. 2.0. At the same time, when the car is fully loaded, the pressure in them increases to 2.4 atmospheres. This method is completely unacceptable for some cars, therefore this method can only be used as a temporary one. for example, on the road, when you were unable to find out the recommended data using a pressure gauge.

### What to pump up

Bicycle luggage requires maintenance and pumping very often. Even on the most “hardy” city and mountain bikes, it is required to check and pump up the camera every 2-3 weeks, since the air leaks not only through the nipple, but also simply through the rubber. High pressure “helps” air molecules find their way through an insufficiently dense chamber.

“City”, or, simply, budget bicycles, it is enough to pump up once every 2-4 weeks, mountain bikes. at least once every two weeks, road bikes. once a week, and road and sports bikes. before each trip.

Therefore, the pump is not only an emergency accessory that is used only when a punctured wheel is changed, but also a necessary part of the preparation for departure. Active cyclists should consider purchasing two pumps:

• portable. as part of an emergency kit or on long trips;
• stationary with a stop and a pressure gauge. for periodic maintenance of your tires.

By the way, an ordinary car pump perfectly takes the place of a stationary pump. It is also suitable for bicycles, shows, shows exactly how many atmospheres are pumped up, and does not take up additional space. Some people prefer to pump up on “professional” pumps at gas stations, but the lack of their professional tool can play a bad joke in the event of an unexpected situation or when you deviate from the standard route.

## What pressure should be in tires R13 R14 R15 in winter and summer

Not every driver pays attention to the tire pressure of their car. But the safety on the road, handling and maneuvering of the car sometimes depends on the pressure in the tires. In addition, the tire pressure level affects:

• for fuel consumption,
• uniform wear of the wheel itself,
• can cause hernias on the wheel court.

If the pressure in tires r13 and r14 is increased, then, for example, when hitting an obstacle, the tire may even explode. Incorrect tire pressure r15 will also affect maneuverability when cornering, turning, etc. Best of all, at different levels of inflation of car wheels, the following figure will show.

As you can see, already by the tread wear, you can determine what the problem of pumping the rim is, but it is better not to bring this up to this, but to maintain a certain atmosphere at the required values.

The tire pressure must be checked at least once a month. Professional drivers check every 2 weeks and before every long journey. And an external inspection of the wheels should be daily before starting the car engine. Although if you are a happy owner of low-profile tires, then it is impossible to determine what pressure should be in tires by eye.

### Pressure effect

In fact, the optimal tire pressure of a bicycle is a purely individual parameter, which each biker varies within certain limits for himself: for his riding style, for the planned route and the current level of training. The limits are set by technological constraints, which we will consider further.

Here are the main factors to consider when choosing an inflation level:

• high pressure gives “roll”. rolling speed, saving the strength of the cyclist;
• excessively high, in turn, can provoke a breakdown of the chamber against the rim from the inside;
• similarly, low pressure leads to “snake bites”, when a rim on an obstacle or bump pierces the chamber at two points at once and reaches the tire;
• low pressure prevents damage to mechanisms on numerous bumps;
• at low pressure better “grip” and easier to move on rough terrain.

Taking into account all the pros and cons, a single recommendation can be made: the wheels should be inflated enough to provide good traction and not damage the camera. For this, there are standards for what pressure is considered acceptable. We will consider them further.

Approximate values ​​by type of rubber

You can also give recommendations for inflating wheels with different tires.

Seasonal changes

Seasonal adjustments are quite serious, mainly related to mountain bikes. In the summer, you should slightly underestimate the pumping and not rest on the maximum. Hot asphalt also heats up the air inside the chamber, which increases the volume and therefore the pressure. Also, a pumped-over tire wears out very quickly.

In winter, you should sometimes slightly exceed the maximum in order to achieve maximum work from the tread, especially if the rubber is selected with spikes.