Let's talk a little more about tires. When your tire is low do you fill it up by eyeing it or do you check your tire pressure with a gauge? Do you know how much air to put in your tires? On the side wall of the tire it has raised rubber that tells you all the information you need to know. This picture is my car tire, for example the tires on my car say 44 psi. PSI stands for pounds square inch. I want to check tire pressure with a gauge so I have pressure in the range of 40-44 pounds. It is important to get all the tires at the same tire pressure to ensure a smooth ride and better gas mileage.