How does tire temperature affect tire pressure?

How does tire temperature affect tire pressure?

According to Ideal Gas Law, there is a proportionate relationship for Tire temperature and Tire pressure. When tire temperature increases the tire pressure will also be increased. Changes in pressure will result in different problems for the vehicle. I will discuss the effects of the change in tire pressure later.

Ideal Gas Equation, PV=nRT

In this scenario,
P             =             Tire pressure
V             =             Tire volume
n             =             amount of substance, measured in moles
R             =             Ideal Gas constant
T              =             Absolute temperature

The tire pressure is being measured with respect to the temperature then, any adjustments in the ambient air temperature will also cause the tire pressure to increase. In every 10 Fahrenheit change, the tire pressure will increase or decrease by about 0.8 Psi. There is a rise in the temperature level due to heat generated by the contact force (friction) between the tires and also the ground.  The temperature increase will definitely cause a rise in tire pressure. For overinflated tires, continued increase in temperature and increase pressure would result in the tires to blow. Similarly, with the increase in pressure caused by a temperature increase, underinflated tires will likely feel like a normal pressure tire. Understanding the relationship between temperature and pressure will not let you know that optimizing the tires according to the pressures. You can get a tire pressure gauge to check pressure level. This will maximize your car tires performance and lower maintenance cost in the long run.

Measure cold tire pressure

The general rule of thumb for the tires to be considered cold is when the vehicle has been stationary for three hours or more. There are an estimated 3 PSI fewer differences between cold tire pressures than tires that have been on the road for quite some time.  The tire pressure may be lowered by one to two pounds in the morning before you head out to work due to the cold temperature at night. Tires are being heated up by friction. We think that it is also better to check a few times per month when the car tires are cold. Cold tires are being used to determine the recommended PSI because it is more consistent to have pressures under the cold condition as compare to the pressure that is from hot tires. PSI is the unit a tire pressure gauge uses to provide readings.

In Texas, has a wide temperature range of up to 50°F.

Is there a maximum tire temperature?

We always wonder if there is a maximum tire temperature for tires before the tires start to have problems. There is a proportionate relationship of a rising tire temperature which will also lead to increased tire pressure. The reverse is also true, tire pressure will be reduced when there is a lower tire temperature. Auto manufacturers usually have a recommended PSI (pounds per square inch)of pressure. The assumption for the recommended PSI is that the tires are cold. A typical auto vehicle recommended PSI is 30 – 40, you are still required to check your vehicle’s manual for a more specific recommendation. Hence by increasing tire temperature, it will cause the PSI to be above the recommended.

Disadvantages with high pressure tires

The disadvantages of overinflated tires will result in rapid tread wear and vehicle harder to manoeuvre. Each tire manufacturer will indicate maximum tire pressure. Normally, tires will be about 45 psi max for a family vehicle. Having a higher than recommended tire pressure might cause some safety hazards. Tires with very high pressure will definitely be worn more quickly than a tire that is normal pressure.

Why are high-pressure tires harder to manoeuvre?

Overinflated tires will cause the tires to be very hard and can also be out of shape thus harder to manoeuvre a vehicle compared to the set of tires that is inflated to a recommended pressure. The user may find the road bumpier as the tire is overinflated, it is very uncomfortable if the journey is long. Overinflated tires are unable to absorb shocks from the road when driving past debris. An overinflated tyre has a smaller contact area with the road, which leads to reduced traction. That is extremely dangerous especially in poor road conditions or rainy days.

Why over pressured tires causes rapid tread wear?

 Tires that are overinflated is very hard and sometimes the contact with the road may be reduced due to a change in shape due to the over inflation. Overinflated tires usually show more wear along the centre of the tire and not on its edges due to friction due to the contact.  The tires uneven tread wear will ultimately shorten the overall lifespan of the tire and you will end up paying more to get a set of new replacement tires over time.

In a worst-case scenario, an overinflated tire might also be punctured easily when you travel over road potholes or contact debris. Running on high speed with a sudden tire puncture might result in a road accident.

How much heat can tires withstand?

There is a max heat tires can withstand either the temperature is too high for the rubber compound or pressure is too high.

In an example, based on a 20-inch diameter, the tire will be running 1008 rotations per mile. Hence by driving faster, it will result in a quicker rotation and also leading to greater friction force with the road. This will cause the temperature of the tire to rise, the tire pressure can be risen by a few PSI due to this.

According to rubber tire material, high temperature developed from running high speed may weaken the ply bonds in a tire. When the temperature reaches to about 350 ° F , tire separations will occur before fatigue type failures.

Why overinflated tires are better in some cases

Car racing requires higher inflation pressures in order to have an improvement in steering response and cornering stability up to a point.

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