How to check car tire

1. Make sure the tires are "cold" (vehicle hasn't been driven for more than 2km) so the air in the tires isn't expanded from heat.
   
2. Look in the owners' manual or (on most vehicles) on the inside of the driver's side door for the standard cold tire inflation pressure. This number is the lowest PSI one would inflate the tires to and is suggested by the car's manufacturer. Read below for reasons inflation may be placed higher.
3. Unscrew the valve stem cap from the valve stem on the tire. The valve stem is a black pencil-sized extension near the hubcap, about 1" (2-3 cm) long.
4. Press the air pressure gauge onto the valve stem and record the reading given. If there is a hissing sound, the gauge is not tight enough for an accurate reading. The angle of the gauge may need to be adjusted.
5. Note that if the reading is the same as the manual's specifications, you are done after checking all other tires for the same pressure. If inadequate pressure is in the tires then fill air in the tires. Make sure you put in the correct amount
6. Replace valve stem cap. The cap does not hold air in, but it keeps dirt and moisture away from the valve mechanism in the valve stem, which does hold air in.