The correct amount of air is almost always written on your car, not something you guess. For most cars it ends up around 32–35 psi when the tires are cold, but you should use the exact number listed for your vehicle, not a generic value.

Find the right pressure

• Look for a sticker on the driver’s door jamb; it lists the recommended tire pressure (in psi) for the front and rear tires, and sometimes for a fully loaded car.

• If you don’t see a sticker, check the owner’s manual under “Tires” or “Specifications” for the recommended psi.

• Ignore the big “max pressure” number on the tire sidewall; that is a maximum the tire can handle, not what you should fill to for normal driving.

How to set the pressure

• Check and fill tires when they are “cold,” meaning the car has been parked for a few hours or driven less than about a mile, because driving heats them up and makes the reading higher.

• Use a tire pressure gauge: remove the valve cap, press the gauge straight onto the valve, and read the psi; compare that to your recommended number.

• At a gas-station air pump or with a home compressor, add air in short bursts, rechecking with your gauge until you hit the recommended psi; if you go over, briefly press the pin in the valve stem (often using the back of the gauge) to let a little air out and recheck.

If you tell what vehicle you have (year, make, model), the recommended psi range for that specific car can be narrowed down even more.