What pressure should be in the tires?

If you study the requirements for a car wheel, you can distinguish only two groups: those that you have to pay attention to only once (when buying) and those that need to be monitored constantly. Among the latter, there is such a criterion as tire pressure.

What is tire pressure and how is it measured?
At the initial stage, the tire acquires the necessary rigidity due to the correct proportions of the components in the rubber. But you can start using it only by pumping in the necessary amount of air, which creates internal resistance. The force with which it acts on the tire is the pressure in it.

Service technician measures tire pressure

The most common units of measurement are bar (Russia) and PSI (Europe and USA). In the first case, pressure is measured in atmospheres or kilograms per cm². And the second uses the ratio of pounds per square inch. Converting PSI to bars is easy: just divide the value by 14.5 (or do the opposite if you need to convert bars to PSI).

What does tire pressure affect?
A number of important characteristics depend on whether the wheels are properly inflated.

Controllability. The easiest way to understand that the tire pressure is incorrect is to follow the behavior of the car. A stiffer ride than usual, when every bump and pit is felt, and low brake sensitivity indicate that the wheels are overinflated. A decrease in reaction to gas and steering turns signal a lack of air in the cylinders.

Tire wear. Incorrectly set pressure leaves a mark on the tread. An overinflated wheel touches the road only in the central part instead of the entire tire area, therefore, over time, it turns out to be worn out in the middle. And the deflated, on the contrary, rests on the canvas with its edges, which are the first to surrender. In both cases, the tires will have to be changed ahead of schedule.

What wear looks like at low, high and optimal tire pressure

Fuel consumption. It happens that tires are pumped intentionally in order to reduce gas mileage. And in this case, it really falls. But this method can hardly be called economical: an extra tank per year will not pay for the premature replacement of rubber. Lowered tires will hit the budget even harder – in addition to tire wear time, the number of visits to gas stations will also increase.

What does the normal rate depend on?
The main difficulty in controlling the pressure in the wheels is due to the fact that there is no single standard for all wheels and cars. This variable is affected by several conditions.

Type and model of the car. If you remember that the tires must provide sufficient resistance to the weight of the car, it becomes clear that the pressure in the wheels of a small car and a crossover cannot be the same, even if you can put wheels of the same diameter on them – these cars have different weights. Therefore, do not take as a starting point the recommendations indicated on the tires themselves. And because of the differences in the production standards of automakers and body sizes of the same class, it is important to know the recommendations for a particular model. Usually this information is placed in the driver’s door opening or on the gas tank cap from the inside.

Wheel diameter. In those cheat sheets that were mentioned above, most likely there will be several values – one for each recommended wheel size with a different disk radius. It’s all about the size of the balloon.

Example of a manufacturer’s recommendation label

Season. As hot air expands and cold air compresses, the tire pressure also changes. Therefore, in winter, the wheels will have to be pumped up by 0.2-0.3 atmospheres more – you can more accurately navigate by the temperature difference: for every 10 degrees there is about 0.1 bar.

Road surface. It is almost impossible to guess which particular road you will have to go today. But you can navigate by the purposes for which the car was purchased: a frame SUV for fishing is unlikely to often drive on flat surfaces, and a comfortable sedan will not have to constantly overcome potholes and bumps. In the first case, it is recommended to increase the contact surface of the tires by lowering them by 0.1-0.3 bar, and in the second case, focus on standard values. And if you have a long trip on the highway, it is worth increasing the pressure by 0.2-0.3 atmospheres.

driving style. Inflated tires combined with aggressive behavior on the road is a dangerous cocktail: a small contact patch with the canvas will not allow you to slow down in time, and the rubber can burst from a sharp blow in a small hole or on a bump. Therefore, impatient drivers should stick to the standard values ​​or even lower the wheels slightly for their own safety. And for calm motorists, it is enough to adjust the average pressure indicators depending on the season and type of roads.

How to track pressure?
Having calculated the optimal value, you can begin to check the current pressure. For this you need a tool and a little theory.

Pressure gauge. This is the name of the device for self-measuring tire pressure. There are three types of pressure gauges: pointer, mechanical and electronic. The former are distinguished by accuracy and fragility, the latter by strength, and the third by very high accuracy (error of only about 0.05 bar) and modernity. It is recommended to check the indicators with such a device at least once a week.

Measuring pressure with a mechanical pressure gauge

Electronic sensor. This built-in device in the car will let you know when the tire pressure changes significantly, but does not eliminate the need for a manual pressure gauge: as any electronics, the sensor may be faulty. To get the full picture, it is better to purchase a pointer or mechanical pressure gauge in pair with such a sensor.

See also: Tire Marking : Decoding Of Symbols On Tires
What to look for when checking tire pressure?
In order not to be mistaken, having even the most accurate instruments, it is worth remembering the laws of physics and following two rules.

Pressure is measured only on cold tires. Tires heated by traffic can affect the behavior of the air inside the wheel and, accordingly, the pressure gauge. Tires are considered cold if they have not been driven for 5 hours or more.

The vehicle must not be overloaded. Excessive mass will cause the air to be distributed unevenly, creating a difference in pressure. In this case, it will be almost impossible to determine the real value.

Methods for correcting the indicator
If the pressure turned out to be too high, it is enough to remove the cap from the nipple and bleed the air, controlling the readings with a pressure gauge. Otherwise, there are several ways to achieve the desired value.

At the service station. This option requires not only money, but also time – not every car service is ready to accept a client without an appointment, even for tire inflation. But here you can relax a little instead of manipulating the pump and dirty wheels, and at the same time check the accuracy of your pressure gauge by comparing its readings with those of a professional one: they will definitely measure the tire pressure at the service station again.

On one’s own. The advantage of this solution is the efficiency and relatively low cost: you only need to purchase a mechanical pump or an electric compressor once. This is also worth doing because trouble with a wheel can also happen outside the city, where there is neither a service station nor a modern gas station with a wheel swap station.