Anyone who owns a car should also own a tire pressure gauge. Tire pressure gauges are used to measure the air pressure that is in each tire. It is useful for any type of tires from bicycles all the way to pickup trucks.
Pressure gauges come in different styles. The one most people have has a ball at one end and a long pencil like form with a slide that pops out when checking air pressure. The ball like the area is a piston that fills with air from the tire when inserted into the tire valve. When measuring it pops the slide out and you can see how much pressure is inside the tire. You can also get the type that has a dial that looks somewhat like a clock. There are also digital pressure gauges where the number is shown on a screen.
Pressure gauges are relatively easy to use. On the side of the tire near the hubcap, you will find a stem or a valve. There is usually a small cover that just twists off. Remove the cap and insert the gauge pressing in firmly. You will hear a small escape of air and you can remove the gauge and see what the pressure is. It is advisable to check the tires before the vehicle has been running. This will give you a more accurate reading.
Not every tire takes the same amount of pressure. It often depends on the tire size and how heavy the vehicle is. You can find requirements on a sticker that is usually yellow in color and placed in the door jam of the car door on the side of the driver. Sometimes pressure requirements are printed right on the tire on the sidewall. Other places manufacturers hide the sticker is under the door for the fueling area and in the glove compartment. PSI is the increment in which air pressure is measured. It means pounds per square inch. Most car tires take about 30 to 40 pounds each tire.
If tires are under inflated you use much more fuel than if they were filled correctly. If they are overfilled you run the risk of having a blowout. In the winter it is often a practice to slightly under inflate tires so that when in contact with winter elements they will stop better. It is questionable as to whether this actually works or not.
Keep your gauge in a dry and cool place. The glove box is a good place to keep it so it is handy. Never drop a gauge because this can damage the measuring mechanism and you will no longer get a good reading. In general, a tire gauge is not in need of calibration so their readings are only close to accurate. There are those that can be calibrated but they cost a lot more money.
Air pressure should be checked in tires on a regular basis because tires lose a little bit of pressure every day they are used. In winter, because of lower outdoor temperatures and because of potholes in the road, air pressure can diminish anywhere from 1 to 2 pounds of pressure per month. When it is hot outside they go down more. Some people check tires with a gauge every time they fuel up the car. That might be a little too much checking. Suffice it to say that checking every three to four weeks will keep your tires in tip-top condition and at the correct tire pressure.
You can find tire pressure gauges at any dollar store for just one dollar. The digital style costs more at about $25. These are necessary for saving money on gasoline and for keeping tires good longer. Gauges do not do any good if they stay in the glove compartment so check your tires every once in a while and when you do always replace the valve cap when you are done adding air.