Tire pressure gauge
A tire pressure gauge is designed to check the air pressure inside the tires on a vehicle. Correct tire pressure is essential for correct vehicle operation and can improve mileage and performance as well. A tire gauge is constructed with a small diaphragm that is attached to a measurement device. The style of gauge can vary from digital to internal slide. A tire gauge is accurate to +/- 3 PSI, however it is possible to buy more advanced models that are capable of determining the pressure to as closely as +/- 1 PSI.
To use a tire gauge, remove the protective dust cap from the tire's valve stem, then insert the tire gauge and press firmly. The gauge will read the pressure inside the tire, add air as needed and recheck. Pressure readings will differ due to change in temperature. Example: If tire pressure is 30 pounds @ 60 degrees it would be about 35 pounds @ 90 degrees, about 5 pound for every 30 degrees. This is a rough estimate because the volume of the tire determines the actual variance amount. Store the tire gauge in a cool, dry place. To determine the proper amount of air pressure for a particular tire consult the sidewall of the tire.