How to Read a Tire Gauge at a Gas Station

Read the tire pressure guage on the air hose while filling

Car tires are manufactured in a way that each style and type requires them to be inflated to a specific amount of air pressure, measured in pounds per square inch. The tire's specific needed air pressure requirement is printed on the outside of the tire near where the tire meets the metal rim of the wheel. If the printed pressure rating is 35 PSI, the tire must be filled to this pressure. A tire pressure gauge is included on the tire fill nozzle at most gas stations, and provides a reasonably accurate indication of the pressure in your tire during filling.

Instructions

1. Press the tire's air hose valve onto the valve stem of the tire and press the filler handle permitting air to enter the tire. Hold the handle down for only a few seconds and then let go of the handle while keeping the valve pressed onto the stem. The tire gauge indicator will be pushed forward showing the current air pressure in the tire.

2. Read the number on the tire gauge where the moving gauge indicator meets with the metal portion of the filling handle, as this is the number that accurately designates the air pressure in the tire. If the numbers are printed on the gauge by tens (10, 20, 30, 40) and there are nine other markings between them with the center mark slightly longer than the others, the center marks represent 5 pounds. For example, the center line between 20 and 30 would be 25 pounds. In this case, each smaller mark represents one pound.

3. Press the handle of the nozzle to apply more air into the tire if the tire is still under-inflated, holding the handle only for ten to twenty seconds at a time. Let off of the handle after every ten or twenty-second interval and read the new pressure reading on the gauge, continuing until the gauge indicates the pressure needed for your given tire and then fill no further.

Tips & Warnings

• Gas station tire gauges tend to experience a high amount of abuse, and they may be off by any number of pounds per square inch. If committing yourself to many miles of driving, a digital tire gauge may provide you with far more accuracy than many of the gauges found at gas stations. Accurately filled tires function in a way that fuel use is reduced.

• Pay attention to any documentation you may have received with your tire, as the manufacturer may recommend keeping the tire under-inflated by 3 to 5 pounds during the hot Summer months. This is generally recommended because air expands in a tire as the temperature of the pavement increases. Hot weather may cause a tire to blow if no room is permitted to compensate for this air expansion.

References

• AA1CAR: Tire Inflation Guages