Why Does the Air Pressure Inside the Tires of a Car Increase When the Car is Driven?

Last Updated on
Illustration of a car in motion showing increased air pressure in tires, with a thermal graphic overlay, highlighting the physics of tire pressure changes while driving.

One of the biggest threats to your safety while driving is one that you won’t be able to see: your tire’s pressure. Since the inflation levels are not visible by the naked eye (unless your tires are flat), It’s crucial to know how to determine and maintain proper air pressure and be aware of the risks of driving with over or under-inflated tires.

Friction develops between the tires and the pavement during driving, creating heat within the tire. This increases the temperature of the air in the tire. By the Ideal Gas Law, when the temperature of a gas rises, its pressure also rises (assuming the same volume).

Thus, due to the rise in the air temperature within the tire, the pressure inside the tire increases. The tire will heat up, however, not due to friction. The tire does not slide down the road, and the friction between the tires and the road is not working. What happens is the fact that the tire is partially circular. It is squeezing due to the car’s weight.

The vehicle moves forward, and the part of the tire that was squeezed is moved to the back and back to the side of the highway and then regains its shape while the portion of the tire toward the front is rolled down towards the road surface and then is squeezed in its turn. This constant flexing of rubber is what causes it to become hot.

The hot rubber heats the air in the tire. As previously mentioned, if you have an unchanging volume, this leads to a rise in pressure.

Unsurprisingly, tire pressure affects several important aspects of vehicle performance, including driving comfort, steering stability, cornering, brake grip, and general handling behavior.

A vehicle driven with low pressure on the tires will negatively impact any of these vital aspects. Therefore, it is important to check tire pressure regularly for optimal performance.

The tire pressures that are specified for your car are set between the car manufacturer and the tire maker. Psi (pound for square inch) is determined by your vehicle’s weight and size, towing capability, and the recommended size of the tire. The pressures are set to keep you secure and comfortable on the road, so adhering to them is crucial.

How Do You Check The Tire Pressure?

After you have figured out the appropriate tire pressure for your car, as suggested by the manufacturer, checking the tire pressure regularly is recommended to ensure that you are in good health.

You can test your tire’s pressure at auto parts stores, mechanics, gas stations, and even your home. To check tire pressure at home, you do need the following:

  • A tire pressure Gauge(Digital or regular)
  • Air Compressor
  • Pen and paper, or your phone

Test the tire with cold tires

The pressure of your tires can change depending on temperature, and the most recommended pressure on tires are those with cold inflation pressure; you should begin with cold tires if you can.

Check the tire’s pressure using the gauge

Remove the valve cap and put the tire gauge on the valve stem with enough force until the hissing sound stops. It should show a reading when the gauge is properly linked with the tire.

Write down the information you have read.

Note down the pressure on every tire, then check it against the recommended pressure you find in your driver’s doors or the manual for owners. It is important to read it thoroughly since, in some cars, the rear and front tires may have different PSI recommendations.

Fill your tires with the psi recommended.

If your tire is not properly inflated, you can use an air compressor to fill the tires. You can buy an air compressor at the auto parts store or a gas station. Be sure to let your tires rest for at least a half hour to ensure they’re cold and the readings are precise.

If you must fill your tires while hot, increase the pressure by 34 psi over the recommended pressure and test them again using your gauge after cooling. It is okay to overinflate some when filling the tires, as you may let the air out using the gauge.

Recheck the tire’s pressure.

After filling the tires, use the gauge on your tire to measure their pressure again and ensure they are within a safe range. Allow the air to escape some if they’re over-inflated. You can do this by pressing the gauge further against the valve’s stem.

How does tire pressure affect Driving?

Overinflation and underinflation can affect the performance of your tires, and serious issues could result. Driving with improperly inflated tires increases the risk of serious accidents by 300 percent.

How the pressure of tires can affect grip?

The grip is primarily related to the contact area dimensions between the tire and the road. The over-inflated tire drastically reduces the contact area, whereas one under-inflated does the reverse.

A bigger contact patch will give you more grip. This is exactly for racers to reduce their tire pressures to make more contact patches on a dry race course.

However, a tire that needs to be properly inflated will increase fuel consumption and improper wear and tear of the tire tread. To a majority of people who commute every day, it could result in a much more dangerous issue, which is hydroplaning.

Hydroplaning can be dangerous when a layer of water is formed between wheels and road surfaces, resulting in the vehicle losing traction and stopping the vehicle from reacting to inputs of control. (Appx2)

Hydroplaning happens when the pressure of the tire pushing the ground is greater than that of water pushing back on the tire. The contact patch size of the force or mass of the tires is the same and directly influences the pressure the tire puts in the roadway.

The bigger the patch of contact (by inflating the tires), the lower pressure it exerts on that same patch. There’s a direct correlation between tension on your tires and the likelihood of a hydroplaning incident.

How does the pressure of tires affect tire wear?

The contact patch is the sole factor determining the tire use and wear direction. It isn’t a good idea for your tires to wear down prematurely because of an under or over-inflated tire.

The pressure of tires influences fuel economy.

The resistance to rolling between your tire and pavement significantly impacts fuel efficiency, and we’re all aware of the reason behind this. Lower tire pressure results in an increased contact patch, which leads to more excellent resistance and, consequently, lower fuel efficiency.

If you drive on under-inflated tires, you run the risk of:

Safety and tire failure. Not properly inflated tires can greatly increase the braking distance and drastically affect handling and steering. Additionally, when the tire’s pressure is low and the tread surface of the tire touches the road, it causes friction.

The friction may cause overheating, leading to blowouts and tread separation in extreme circumstances.

Wear from premature wear can reduce the lifespan of your tires by 15% or more. Inflating your tires wears them on both shoulders outside because the edges are in contact with roads.

Poor gas mileage. Tires that need to be properly inflated will result in lower fuel efficiency because they force your engine to be more difficult to work with. Underinflated tires create more tire surface direct contact with roads, creating more friction and rolling resistance to the pavement.

The result is poor fuel efficiency and higher fuel prices, which can reach 1.3 cents per gallon! Based on the frequency you use your fuel, that can result in hundreds of dollars in a single year.

Conclusion

When a wheel is moving, friction force exerts itself between the wheel and tire, which causes the loss of energy as heat. This heat raises the temperature, and the kinetic energy of gas molecules rises, which causes pressure to increase.

As we drive around in our vehicles, the tire pressure is increased due to the road. Inside the tire, the air is heated, which causes tire expansion because of the pressure force generated by the friction. The pressure of your tires is always a hot issue concerning safety in driving, so it’s essential to be aware of the pressure of your tires to ensure your vehicle’s efficiency and safety.