Tires are probably the most overlooked part of vehicle maintenance, yet very important for operation.
According to the National Highway Traffic Safety Administration (NHTSA), and under-inflation may influence automobile accidents by contributing to:
The correct air pressure for your tires should be shown on the vehicle door edge or post, glove box door or fuel door. It should also be listed in your owner's manual. If you cannot find this information, contact the vehicle manufacturer.
The pressure listed is for "cold inflation pressure", which is the pressure in a tire that has not been driven for at least three hours. As tires warm during driving, it is normal for pressure to increase. Never reduce air pressure when tires are hot.
Inflate tires according to the vehicle manufacturer's recommendations, not the maximum pressure listed on the sidewall. You should never exceed this maximum pressure.
Tires can lose 1 psi per month under normal conditions. Tires also can lose 1 psi for every 10°F temperature drop.
Check tire pressure at least once a month and before going on a long trip. Also, don't forget to check the spare tire to ensure that it's properly inflated and ready if needed.
Air pressure should be checked when tires are cold. Inflation pressure can increase several pounds during a long trip in hot weather.
When checking tire pressure, also inspect tires for uneven tread wear, cracks, foreign objects, or other signs of wear or damage. All tire valves should have valve caps.
Check the air pressure with your own gauge. Some air pressure towers at service stations are inaccurate because of exposure and abuse. Also, do not check pressure by just looking at the tire. A tire can be under inflated by 10 pounds and not appear to be low.