You will need a tire pressure gauge, which you can find at most service stations or auto parts stores. You should check the pressure when the tires are cold, as the friction from driving causes them to heat up and affects the pressure. Check them first thing in the morning or, if you’re already driven the car, Consumer Reports recommends waiting at least three hours for the tires to cool down.
Once you have a tire gauge in hand, this is how to check your tire pressure:
Remove the cap from the air valve on the tire, and put it somewhere you won’t lose it.
Press the tire gauge against the open valve stem for a second or two. It’s normal to hear a hiss of air.
Read the air pressure gauge. For manual gauges, a dial points to the pressure or a bar indicates the pressure by how far it was pushed out. The pressure will appear onscreen on a digital tire gauge.
Compare this number with the recommended tire pressure.
Replace the tire’s air valve cap. (Hold off on this step if you need to adjust the air pressure.)
Repeat this process for each tire.
How to Inflate Your Car’s Tires
If your tires are lower than the manufacturer’s recommendations, follow these steps to inflate the tires:
Park close enough to the air compressor so you can reach all four tires with the hose.
If the valve caps are still on, remove them.
Press the hose nozzle down on the valve stem. Air may flow automatically or you may need to press a lever. You should notice the tire inflating and feel air flowing through the hose.
Remove the hose fitting or release the inflation lever. Check the air pressure, as described above, using the gauge on the hose or your own tire gauge.
Repeat steps 3 and 4 as needed until the tire is inflated to the correct psi.
Repeats steps 3-5 for the vehicle’s other tires.
Once the tires are inflated properly, replace the valve caps
When You Should Check Your Tire Pressure
Tire air pressure should be checked once a month using the same tire gauge, says The Family Handyman. Remember to check when the car has been parked for at least a few hours and the tires are “cold.” Tire pressure can vary 1-2 pounds per square inch (psi) for every 10-degree difference in ambient temperature, says Car Talk — the psi typically rises in the summer heat and drops when it’s cold outside. If you’re in the habit of checking your tires every month, you can adjust the pressure as it fluctuates throughout the seasons.