Importance of Proper Tire Inflation

A tire is a pneumatic system, which supports a vehicle's load. It does this by using a compressed gas (usually air) inside to creat tension in the carcass plies. It's important to realize that a tire carcass has a high-tension strength, but has little or no compression strength. It's the air poressure thta creates tension in the carcass and allows the tire to function as a load-carrying device.

That's why inflatoin is so important. In an inflated, but unloaded tire, the cords pull equally on the bead wire all around the tire. When a tire is loaded, the tension in the cords between the rim and the ground is balanced or relieved. The tension in other cords is not changed. Therefore, the cords opposite the ground pull upwards on the bead. This is the mechansim that transmits the pressure from the ground to the rim.

In addition, a tire must transmit handling (acceleration, braking, and cornering) to the road. Cornering forces are transmitted to the rimin a similar manner to load. Acceleration and braking forcesrely on the friction between teh rim and the bead. Inflation pressure also supplies the clamping force, which creates fricitoin. A tire also acts as a spring between the rim and the road. This spring characterisitic is very important to the vehicle's ride. Too high an inflation pressure cause the tire to transmit shock loads to the suspension and reduces a tire's ability to withstand road impacts. Too low an inflation pressure reduces a tire's ability to support the vehicle's loadand transmit cornering, braking, and acceleration forces.

Inflation problems

Under-inflation can cause may tire-related problems. Since a tire's load capacity is largely determined by its inflation pressure, under-inflation results in an overloaded tire. An under-inflated tire operates at high deflaction resulting in decreased fuel economy, sluggish handling and may result in excessive mechanical flexing and heat buildup leading to catastrophic tire failure.

Correct inflation is especially significant to the endurance and performace of radial performance tires. For example, because of a performance redial's aspect ratio and design, it may not be possible to look at a radial tire and actually see under-inflation of 5 psi. However, under-inflation of 5 psi can reduce a performance tire's tread life by 25%. A typical tire may lose 1 to 2 psi a month, if not checked and adjusted.

Temperature Effects

Air pressure is affected by temperature. The air pressure in a tire is no exception. Typically, an inflation pressure can change by 1 psi for every 10 degrees in Fahrenheit of temperature change. Higher temperature means increased pressure.

For example, if a tire is inflated to 35 psi on an 80 degree F July day, it could have an inflation pressure of 23 psi on a 20 degree F six months later in January. This represents a normal loss of 6 psi over the six months and an additional loss of 6 psi due to the 60 degree F temperature change. At 23 psi, this tire is severly under-inflated. All tire makers recommend that consumers check their tire inflation pressure at least once a week, and as often as possible when tires are cold (ambient air temperature and if the vehicle has not been driven for several hours).

Excessive inflation loss (more than 2 psi per week), visible damage and irregular wear, or tires experiencing severe impacts, vibration, or pulling require removal along with an expert inspection of tire and rim to determine reparability or the need for replacement. Damaged tires may fail suddenly or burst upon re-inflation, resulting in serious injury.

For an expert evaluation of your tire please see our service department. http://www.saturnofsiouxfalls.com/

Article by Tire Review Magazine