How to Use PSI Tire Air Pressure

by Anthony Smith

Overview

The acronym PSI stands for pounds per square inch, and it is a unit of measure of pressure. It is commonly used when referring to the inflation of automobile tires. A person who is unfamiliar with the effects of tire inflation on a vehicle may not know how to use PSI numbers, but with a little guidance and information, anyone can do it.

Step 1

Know the proper tire inflation in PSI for your vehicle. Contrary to popular belief, the numbers printed on the sidewall of the tires are not necessarily the recommended inflation pressure for the vehicle. This can be found in the owner's manual for the vehicle.
Step 2

Buy a good quality tire pressure gauge and use it to take a PSI reading on all of your tires at least once per month. The tire pressure should be checked when the tires are cold and have not been driven on for at least three hours.
Step 3

Take a tire pressure reading by removing the cap on the valve stem of the tire and firmly pressing the tire gauge fitting over the valve stem. To get an accurate reading, make sure that the tire gauge fitting and valve stem briefly form an airtight seal. You will know you have accomplished this when the "hiss" that starts when you push the fitting onto the valve stem stops. The air pressure will cause the gauge to register a PSI reading.
Step 4

Remember to get a PSI reading for your spare tire when doing your check. Keep in mind that this tire may require a different pressure than the others, especially if it is a smaller, "donut" spare.
Step 5

If your tire pressure is below the recommended PSI, add air to your tires in the morning, when the air is cooler, in order to reach the tire's recommended PSI.