Maintaining the correct air pressure in your car's tyres not only increases your safety on the road, but improves the car's petrol mileage. The correct air pressure for a tyre is written on it's side and listed as a number of pounds per square inch (PSI). Once you have located that number, you can take your car to check the tyre pressure at a petrol station.
Go to a petrol station that has an air machine for filling tyres. They are usually located outside and look like small boxes with long, black hoses attached to them (sometimes they are marked 'Air'). Pull your car up to the machine so the machine is centred on your car. This way, the air hose is sure to reach all of your tyres.
Pick one tyre to start with and locate the PSI label on the tyre. It will be written on the side of the tyre: Find the numbers or letters of the brand of tyre and at the end of that label, typically given in a parentheses. For example, the side of a tyre may read: PR300345 All Weather (30-45 PSI). This tyre requires between 30-45 PSI to operate safely.
Remove the tyre air stem cap. The air stem is a black stem that will be protruding through your rim, with a screw-on cap.
Pull the air hose over to the tyre. Most air hoses have a trigger assembly on the end. The tip will fit over the end of the air stem. Press the tip down firmly on the stem for two seconds, and the built in pressure gauge on the top of the trigger assembly will extend a pressure reading bar. Pull the tip of the air hose off the air stem. If the air hose does not have a trigger assembly, purchase a tyre gauge from the petrol station or from an car parts supplier. Press the tip of the gauge over the stem and the pressure bar will extend out the back. Remove the gauge.
Read the pressure bar to see the current PSI level in your tyre. The pressure bar is marked with a series of lines and numbers. Most pressure bars use lines to indicate two pounds of pressure in-between whole numbers. For example, there will be four lines at the very tip of the bar and then the number 10; then four more lines and the number 20, etc. The point where the pressure bar has stopped extending from the case indicates the number you should read to determine the PSI level in your tyre.
Add air, if necessary, by pressing the tip of the air hose down on the air stem and holding the trigger in. Wait a few moments, release the trigger and remove the air hose. Check the tire pressure again. Make sure you have pushed the pressure bar back in before beginning the process, or your reading will not be accurate. Repeat until you have the correct PSI level in your tyre.
If you can't locate the PSI range on the side of the tyre, check out the KwikFit, Tyre Safe and Pure Tyre websites listed in the Resources section to get the required tyre pressure for your car.
Do not drive on underinflated or overinflated tyres. Both instances greatly increase your chances of an accident through tyre failure or loss of steering control.