Tire pressure measures the maximum amount of air pressure a tire can handle. The maximum tire pressure rating, measured in pounds per square inch (PSI), is listed on the inside edge of the sidewall so drivers can properly inflate their tires. Tire pressure is lost on a daily basis through practical use, but it can dip significantly due to changes in temperature and altitude. A couple of pounds of air are usually lost each month in cold weather, and even more air is lost during warm months.
Facts about tire pressure