Tire Pressure and Temperature
Using the proper tools to arrive at the correct tire pressure is critical to making your race car perform at the optimum level.
Air is about 78% nitrogen and it is free. But air also contains about 21% oxygen and water vapor. Filling a tire with 100% nitrogen has some important advantages over filling with air.
One is that nitrogen molecules are larger than oxygen molecules, so tires leak less gas over time. Another benefit is that pure nitrogen doesn’t heat up as fast, so tire pressure gain is significantly less!
Another commonly overlooked factor that affects tire pressure is the temperature of the tire when the pressure is set before hitting the track. Since air or nitrogen is a gas, it expands when heated and contracts when cooled.
The rule of thumb is that for every 10 degree Fahrenheit change in air temperature, your tire’s inflation pressure will change by about .8 psi (up for higher temperatures and down for lower).
For example purposes, let’s assume that your two rear tires are sitting in direct sunlight with an ambient temperature of 85 degrees. The two front tires are left inside the trailer where the temperature is only 65 degrees. Prior to hitting the track for practice, all four tires are inflated to 30 psi. When the two front tires are heated to 85 degrees (same temperature as the back tires) the actual pressure in these two tires will have increased to almost 32 psi!