How To Check Your Car's Tire Pressure and Inflate Tires

Drive Safely While Saving Money and Gas


  • Filling Up

    Filling Up

    Most gas stations have air compressors (which attendants will often turn on for free). Many compressor hoses have built-in gauges that show when you've filled the tire to the right level. | June 12, 2014

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Underinflated tires increase tire wear, reduce fuel economy and can potentially cause a blowout.

Inflating your car's tires to the specified pressure is important. But simply looking at the tire and checking the information on the sidewalls is the wrong way to do it. If the tire looks slightly under inflated, chances are the pressure is way below the recommendation. Make it a habit to check and refill your tires at least once a month. Here's how.

Checking Your Tire Pressure
Here's how to check the pressure in your car's tires with the least amount of muss and fuss. You'll need a tire pressure gauge. These are available at auto part stores and cost about $10.

1. Find the tire pressure level recommended for your car. This information is usually on a yellow sticker in the doorjamb on the driver side (and it is also contained in the owner's manual). It might call for different pressure levels for the back tires and the front tires or different pressures depending on the load or use of the vehicle.

2. Check the pressure when the tires are cold, as this is how the automakers list these recommended tire pressures. Tires heat up as you drive, so measuring them while they are hot will give you an inaccurate (overly high) reading. They take about a half hour to cool down. You also can just check the tires first thing in the morning.

3. Unscrew the valve cap and set it to the side or in a pocket where you won't lose it.

4. Press the tire gauge onto the valve stem. There might be a slight hiss as you press down on the valve stem and again as you release it. You only need to do this for a second or two, long enough to get an accurate reading.

5. Read the tire pressure on the digital gauge. You might consider writing down the pressure of the tires as you go around the car. You can refer to this when you fill up the tires.

Now you can compare the tire pressure readings you got with the specified amount called for by the manufacturer (on the doorjamb or in the manual). If the level of pressure in your tires is below the specified amount, you need to fill the tires with air.

For example, the sticker on the doorjamb may say that the recommended level is 32 psi (pounds per square inch). When you check your tire you find it is 29 psi. You need to bring your tire pressure up to spec. It's estimated that for every 3 psi below spec, you burn 1 percent more fuel (and add 10 percent more tire wear). It's not uncommon to be 10 psi below spec, which would waste 3 percent more fuel and increase tire wear by 45 percent.

Filling Your Tires
There are at least two ways to refill your tires to bring them up to specification. You can go to an auto parts store and buy a portable air compressor. If you do this you can refill your tires at your house or in your garage.

Most people, however, will just refill their tires at a gas station. Even though many stations charge 75 cents to use their air compressors, you can usually get the attendant to turn on the machine for free.

Adjusting Your Tire Pressure
Here are the steps needed to adjust the pressure in your tires:

1. Pull your car in close to the air compressor so the hose reaches all four tires.
2. Remove the valve stem caps and set them to the side or in a pocket.
3. Insert coins or if the gas station attendant turned it on, you will hear the compressor motor beginning to run.
4. Press the hose fitting down on the valve stem and press the lever. You should feel air flowing through the hose and hear it inflating the tire. This can take a little effort to hold the hose on the valve stem.
5. Check to see when you have enough air pressure in the tires by releasing the inflation lever. The gauge on the hose fitting will show if you have approximately enough air pressure. You can check it again later with your own gauge. At this point, it is better to slightly overinflate the tire.
6. Adjust the pressure in all the tires in the same way. (Note: If the tires are warmed up, you can inflate the tire pressure to 3 psi over the specified amount as a general rule of thumb, but you'd still want to officially check the tires later.)
7. Recheck the tire pressure with the digital gauge. If the pressure is too high, press the gauge down just far enough to release some air from the tire. Check it again.
8. Replace the valve caps on all the tires.

Now it's time to enjoy improved fuel economy, reduced tire wear and (above all else) safe driving.

Comments

  • a1cmugs2 a1cmugs2 Posts:

    I don't agree, The label on the door jam maybe at good reference but every manufacture of tires have different inflation. Some tires have 45Lbs some have 32lbs and this varies by brand of tire. You need to look at the tire and see what the tire pressure is cold. The sticker on the door jam maybe for the tires that were on the vehicle at time of production but if most operators have replace there tires the brand of tire may have different cold pressure inflation.

  • jweebs86 jweebs86 Posts:

    You can also buy a good quality air compressor at most hardware stores and keep it in your garage, rather than buying a cheap portable one at an Auto Parts Store. This is a good way to go if you have several drivers in your home and want to check all of the cars at once.

  • jweebs86 jweebs86 Posts:

    In response to a1cmugs2: From my experience, the pressure ratings on tires are often the maximum pressures that the tires should ever be filled to. Even if a tire has a maximum pressure of 45 PSI, it doesn't mean that this is the best pressure for your car.

  • I'm cheap so I used an analog pressure gauge and a bike floor pump. Although it takes some effort to manually inflate the tire, after you do it a few times you can roughly calculate how many pumps it will take to raise the pressure 1 unit, which is pretty nice. Also, you get a decent workout when inflating all of your tires.

  • ajb999 ajb999 Posts:

    Should the pressure be checked when the car is fully loaded to capacity or before it is fully loaded? Several hundred pounds added to the back of a minivan should increase the pressure reading versus unloaded. Will pressure be too high if filled to recommended level and then the load is put in?

  • carvel carvel Posts:

    If “cold” always meant the same temperature, and if the temp. inside tire shops was always “cold”, I’d be happy. I phoned Goodyeare Tire Co. & asked the customer service rep., “If I inflated my car tires to 32 psi at zero degrees fahrenheit, and then heated them up to 100 degrees, what would be the pressure in the tires?” He replied, “That is a secret. I’ve heard that question before, and the answer is a secret.” Personally, for each car I own, I make up a chart w/2 columns: Temp. & pressure. I assume that the cold temp. outside is ALWAYS zero. Then I write in pressures, w/ the top pressure being whatever is the “Maximum Pressure” on the tire’s sidewall. By filling in the remaining blank spaces, I can assume that the tire isn’t underinflated any day of the year. Of course, all this presumes that car tires are designed to run safely at 44 psi at 100 degrees, etc. I wish tire manufacturers would publish a “tire pressure safety margin” range of pressures for each temp. from zero to 100 or 115 degrees. I forbid tire mechanics & oil change shops from checking pressure on my cars, so they won’t let air out.

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