Modern tubeless tires are a system of three parts that work together in a literally airtight system.
First is the tire itself, which is the black rubber part, even though a modern tire is much more than a just a rubber ring, it has steel belts and is composed of rubber and rubber polymers. The second part is the rim, or wheel. The rim is the metal part, either aluminum or steel, that the tire fits around and is actually attached to the car by the lug nuts and bolts. The last element, and the most important one for us, is the valve stem. This is the part that protrudes from the rim and into which the air goes.
First, look at the tire, the valve stem should be sticking out from the rim, it will be either black rubber, black rubber capped with metal or all metal and will be between one inch and three inches long. Remove the valve stem cap by twisting to the left. Make sure to put the valve stem cap where you can find it. This cap protects the inside of the valve stem from moisture and dirt.
Place the air pump valve over the valve stem end and push down. If the air pump has a gauge on it this gauge should give you a reading. Push down harder and you should hear the air going into the tire. A note on commercial air pumps; do not trust the gauges on them. Chances are they have not been calibrated since they were installed. Buy a good air gauge from an auto parts store and use it to measure the air in your tire. You should check the air pressure in your tires about once a month.
After the tire is filled with sufficient air remove the air pump and check the air pressure in the tire with your store bought gauge. You may need to remove or bleed some air out, if you have over filled the tire. You bleed the air by pushing on the valve stem with the reverse of the air pump; you will hear the air escaping. Or you may have to return to filling the tire if the air pressure is still too low. Now repeat this process with all the tires on your vehicle. Once the tires are correctly inflated replace the valve stem covers.
The question often arises as to how much air your tire needs. Air pressure is measured in Pounds per Square Inch, or PSI. There are two places to find out how much pressure your tires need. The first place is in the car owner’s manual which will also provide the correct PSI for each tire and particular driving conditions. The second place is on the inside of the driver’s door frame which should have a sticker or plate that lists the best air pressure for each tire and conditions.
Do not use the PSI listed on the side of the tire. The PSI listed on the side of the tire is the maximum safe PSI for that tire. It is not the recommended PSI for that particular car.
Properly inflated tires are important as a safety consideration for your car; they insure fuel efficiency and are part of the ride comfort. Improperly inflated tires rob you of gas mileage and may be a safety hazard.