Bar and psi are tire pressures. Measurement and translation of quantities

All owners of wheeled vehicles - motorists, motorcyclists and cyclists - have to monitor the pressure in the tires. For each of the modes of transport there is a range of optimum pressures, which, among other things, you can learn by marking the rubber.

Most often you have to deal with units bar or psi. The pressure in inches per square meter (psi) is used to mark tires produced in England and America. Ba r-unit for measuring pressure, adopted in European countries, including ours. It is almost equivalent to a technical atmosphere.

Most modern manometers have a double scale on which you can immediately see the pressure in bar and psi. Still there are electronic manometers for motorists, they choose the desired display mode. But the hand-to-hand translation of the psi into the bar and back has to be done quite often, since there are not any measuring instruments for every motorist.

For a single calculation, it suffices to use the equality:

1 psi = 0.069 bar

1 bar = 14.504 psi

Accuracy of three decimal places is usually not required. In most sources you will find that 1 bar ~ 15 psi. But the higher the pressure, the greater the error in calculating according to this approximate equation. Therefore multiply by 14.5 - the most optimal option.

Translate from bar to psi pressure and you can use special electronic gauges, which are sold in stores for motorists. But if there is no such device, and the transfer of psi units to bar and back should be done often, it makes sense to make a table. In the garages, tables are used with a range of values of 1 and 0.1 bar or 5 to 15 psi. And if you have access to the Internet, it's easiest to translate the value using the search calculator.

Errors in the measurement

The pressure in the tires is quite dependent on the temperature, so the gauge reading will differ in the warm and cold season, even if the same volume of gas is pumped. The tire heats up also during driving, from friction to road surface.

Measurements are usually carried out "cold" when the car has traveled no more than 3 km at low speed or stayed at least 2 hours. When the condition was not met, it is necessary to subtract 0,3 bar ~ 4.5 psi from the received indications. The pressure measured in winter and summer can differ much more: with decreasing temperature for every 5 degrees Celsius, the reading decreases by 1 psi.

The car or motorcycle tire every month naturally loses about 1 psi (the pressure in the bicycle tire drops by as much as 15 psi). Thus, with a smooth increase in the average monthly temperature during the spring period, it is often not necessary to pump up automobile tires. And in the autumn and especially with a sharp cold snap - this is a guarantee of safety on the road.

It is sometimes difficult for a layman to determine the exact pressure, since in mechanical devices the error appears almost always. Now you can buy pressure gauges with "smart" chips, which correct for temperature. Whether it's worth buying a multifunctional device, trusting your intuition or the skill of a STO employee - it's up to you. The main thing is that the tire pressure is suitable for a comfortable and safe ride.