What is PSI and how to convert pressure to atmospheres
One of the main tasks of every car owner is to maintain the correct pressure in the tires. For this you need very little. It is required to arm a pressure gauge, connect to the onboard network or to the battery some compressor and start pumping the wheel.
Thus, domestic motorists are used to the fact that the pressure in all the manuals and operating manuals is always specified in atmospheres or, at most, in bars.
But recently the situation has changed. More and more often it is possible to see cars, manufacturer of which indicates the recommended optimum pressure in such unit of measurement as PSI.
And here, the domestic motorist is confused. After all, everyone is used to the fact that the wheel should be pumped to about 2 atmospheres. And here are the values, many times exceeding them. What it is and how to correctly decipher PSI – these are the key questions in such situations.
Units of Pressure Measurement
There are a few basic variations of what units car tire pressures can be measured in.
- Atm (atm);
- Bars (bar);
- pascals (Pa);
One wheel, and how many ways to measure the pressure in it.
Motorists are accustomed to the fact that the technical documentation prescribes the pressure specified in atmospheres or bars. This is what should be maintained in the wheels during the operation of the vehicle, because this is how the automaker has calculated that the machine will work in optimal conditions. That is, the best ratio between stability, fuel consumption, traction, acceleration and braking dynamics.
It is necessary to adhere to the rule that the wheels on the same axle should have the same pressure. Otherwise, the steering ability will be disturbed, there will be uneven wear of rubber, etc.
At the same time, it is allowed that the wheels on different axles have different pressure. For example, when the trunk is heavily loaded, and then the rear wheels can be inflated by 0.1-0.2 atm more than the front ones.
It’s important to understand the units of measurement and how different they are and whether one unit can be converted to another.
A Little About Atmospheres
As mentioned above, in most cases the unit of pressure is an atmosphere. But only not everyone understands what it even means.
Atmosphere refers to a pressure that is equal to 1 kilogram per cm2. This is about 0.1 MPa (megaPascal).
There are 2 standards for atmospheres:
- Technical. It is denoted as at or at. In the case of technical, 1 at corresponds to 735.56 mm of the mercury column.
- Physical. This is already atm or atm. The difference is small, as it is 760 mm of the mercury column.
Regarding the pressure in the wheels of the car, it is customary to put an equal sign between the technical and physical atmospheres.
It should not be forgotten that the difference between 1 atm and 1 bar is also insignificant. The latter corresponds to 750.06 mm. of the mercury column. Because of this, 1 atm=1 bar. As far as motorists are concerned, the slight error between the two units of pressure measurement is not taken into account. It will not affect the condition of the tire in any way.
Read also: GAP insurance as an additional payment to a hull insurance or a guarantee of preserving the value of the car
Getting to know PSI
Now we should talk about what the unit of measurement is PSI.
When applied to tires, PSI can also often mean pressure. This unit of measurement is widely used in the U.S. and other countries that use the inch system of measurement.
If you ask a person who lives by the inch (English) system what tire pressure means, he will answer about the same as our man about PSI. Probably nothing at all, since such units, familiar to us, are not used there. And so you should not worry about it. Everything can be fixed.
Dealing with the question of PSI, it is important to note the following.
1 unit of PSI corresponds to 51,715 mm of the mercury column. This is about 14 times less than in the case of the atmosphere. It is measured in pounds per square inch.
And it is legitimate to ask how much PSI should be to create the correct pressure in the tires of any vehicle where other units of measurement are used.
In the case of domestic motorists, it becomes necessary to convert one unit to another. This will go a long way in figuring out just how much PSI should actually be in your car’s tires.
Actually, the translation between atm and PSI does not cause any great difficulties. There is no need to be a mathematical genius and do complicated calculations in this case.
If you want to make sure your tires are at the right pressure, but don’t understand how many atm’s are PSI, you can use one simple rule of thumb.
To convert PSI to our more familiar bars or atmospheres, just divide that value by 14.
Suppose you have PSI units in your technical documentation, but you can create tire pressure by relying on a pressure gauge with a unit of bar. It’s elementary. You take the PSI that the automaker specified in the regulation and divide it by 14.
Let’s assume you know exactly how much PSI your car’s tires are supposed to be properly inflated according to the technical regulation. The documentation says that the tires should be inflated to 26 PSI. Simply divide 26 by 14, and you get the required value. You end up with an output of 1.8 atmospheres or bar. There is no fundamental difference between the last two units.
As you know, for many cars, the pressure at 1.8 atm is quite normal and quite common.
Guided by this principle, you can easily quickly determine how much PSI should be in your car tires to ensure proper and optimal car behavior.
If you need a more precise measurement, which is hardly necessary for motorists, then a pressure chart will come to your aid. It clearly shows what number of atmospheres or bar corresponds to PSI, and vice versa. But to maintain tire pressure, it’s usually enough to simply divide the pressure in the inch system by 14. And everything will immediately become clear and obvious.
There is no urgent need to sit with a calculator all the time, to multiply or divide something in a column, at all. If you own one car, constantly operate it, but in the recommendations prescribed values PSI, then it will be enough to do the calculation once, translate the values into bars or atmospheres and continue to operate quietly.
It is not necessary to buy a new pressure gauge, throw away your old gauge, which shows atm or bar. For convenience, you can check the table after the calculation, and then on the inner surface of the gas tank hatch with an indelible marker write what pressure you should have in the tires. Only in the usual units of measurement.
It will be a kind of a memo for the rest of the time, while you drive this car, have not changed to new tires, which are different from the regulated ones, and they may require a slightly different pressure.
Just remember that the automaker may recommend using different tire pressures depending on the season of the vehicle’s use. In the warm season, the values are usually higher, but in winter you need to make the tires softer, provide a larger contact patch with the surface and achieve better traction.
In practice, the pressure units in the form of PSI should not cause any problems and panic. Take this figure, divide it by 14, and now you see what the pressure should be in bars or atmospheres.
How to convert pressure from PSI to atmospheres: the nuances of converting pounds per square inch to physical atmospheres for tires
The tires of an automobile vehicle must always maintain a pressure that allows it to move normally without inconveniencing its occupants.
Thus, such a task for the motorist is regarded as one of the highest priorities. If the pressure level in each of the tires is normal, it is a guarantee that driving becomes safe and fuel consumption does not exceed the established standard.
The operation of the vehicle in the conditions of Russia is different because it is considered more usual for motorists to measure the pressure level of the tires in atmospheric values. However, the use of new generation machines makes a little retraining, because, enclosed to them instructions for use contain data values in other units of measurement. These are PSI.
It is worth to understand why exactly it became necessary to introduce such units in practice, as well as to learn how to translate PSI into a more understandable atmosphere without any problems.
Pressure units used in practice
The use by Russian motorists of atmospheres, as values to measure the pressure level present in the tires of the wheels is justified by the long practice. However, this option is not considered the only one, as all over the world, such value has long been used to measure differently.
Different countries use different units of measurement. Somewhere, the level of pressure that is present inside the tires is usually measured in bars. For someone, the way using Pascals along with PSI became more understandable.
To make it clearer which value and how it differs from the other, it is important to understand thoroughly the different units of measurement:
- Atmosphere is commonly referred to as the pressure value when a mass weighing one kilogram is applied to an area the size of one centimeter squared. The atmospheric value can be a physical concept, or it can be a technical term. The first case refers to seven hundred and thirty-five and a half millimeters of mercury column. The other case refers to seven hundred and sixty millimeters. If it refers specifically to automobile tires, then both the atmosphere, technical and physical, are quite identical;
- As for bars, they are in practice one-to-one ratio to atmospheres. In reality, though, one value corresponds to seven hundred and fifty-six hundredths of a millimeter of mercury column;
- The rarest unit that can be used for practical purposes in relation to tire pressure is the Pascal. But if you increase your level of general knowledge somewhat, you will know that one atmosphere corresponds to a value equal to one hundred thousand one three hundred and twenty-five Pascals;
What is PSI?
The best-known PSI for the Americas is naturally indicated in many of the manuals for the models produced by the manufacturing firms of that country. The pressure value of one pound per inch squared is what such a unit of measurement means.
That is why it is so important to understand and be able to quickly translate PSI units that are marked in the technical documentation of a particular car brand into understandable and so convenient atmospheres.
Translating PSI units into atmospheres
When it comes to use for an automotive vehicle, it is worth noting that the one-to-one ratio, as noted earlier, is used in relation to values for bars and atmospheres.
And despite the fact that in what follows we will be talking exclusively about atmospheric values, but at the same time it can also be clearly attributed to values expressed in bars.
After correlation between different units of measurement used in different countries and, accordingly, for different models of automobiles becomes clear, the process of translation of PSI values into atmospheric values will not be difficult at all.
- For this purpose, the indicated numerical value will simply have to be divided by fourteen. If, for example, in the documentation with the performance characteristics of the vehicle there is an indication of the fact that the wheels of the front axle pressure level in each tire must be equal to twenty-eight PSI.
- This is in the case of two people in the cabin. Then such a condition would mean that the pressure value corresponds to two atmospheres or two bars, which is unambiguous.
- Since the arithmetic action of dividing twenty-eight by fourteen gives in the answer a numerical value equal to two.
Thus, it turns out that the pressure value indicated in the attached technical documentation is given in units – atmospheres, and the device itself, which is designed to measure the indicators, gives results in the form of PSI, it will be necessary to make a simple calculation.
Multiply the pressure reading in atmospheres by the number fourteen. Then the result will show the pressure value in PSI.
Note this. In practice it is quite common to have the information about what pressure is recommended for a certain brand of car directly on the gas tank under the hatch.
It may be that the information is stated in PSI units. The pressure gauge device used to measure the pressure, however, is set to display the measurements in bar or atmospheric units.
For such cases, you will need to do the following once. Translate the numerical values using a factor of fourteen. Then take a suitable sticker to write the information on it in the unit of measurement that is most suitable and convenient for you.
Tabular form for translating pressure values
The numerical value of fourteen is the average value. To save yourself the trouble of more meticulous calculations, it is convenient to use the table version: It can always be found on the Internet to print out or rewrite for your needs.
7.31 psi = _______ mmHg psi x 760 mm Hg = 378 mm Hg psi torr = _______ kPa torr x kPa = 152 kPa. 760 torr psi = ________ kPa psi x kPa = 131 kPa. 202 kPa = ________ atm. 202 kPa x 1 atm = 1.99 atm kPa. Rmv psi.