How To Check & Adjust Tire Pressure

Learn how to check and adjust the air pressure on your car tires.

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• Automotive: DIY • Automotive: How-To
• Automotive: Maintenance • Automotive: Tips & Tricks

Matt Anderson's Take
An improperly inflated vehicle (or bike) tire is both inefficient to drive on and flat out dangerous. Driving your vehicle on tires with the incorrect amount of air in them can lead to poor fuel economy, premature and uneven tire wear, and even blowouts that can cause injury or death.

Not only is it important to fill your tires to the recommended air pressure, it's just as important to check your tire pressure frequently. Why? Because tires lose air constantly. That's right, your car tire is leaking air right now. Sure, it's probably an incredibly slow leak but it's normal for a tire's air pressure to drop and require a topping off every month or two. Much like a balloon will deflate over time, so does a tire.

Fortunately, checking and filling car tires is incredibly fast and easy to do. Here's step-by-step directions on how to check and fill your tires properly.

Step 1: Find The Recommended Pressure


Every vehicle has a Tire And Loading Information sticker on it. It should be on the door sill on the driver's side of your car. Just open the driver's door and look for the sticker. Failing that, check your owner's manual.


That sticker will show the recommended amount of air pressure each tire should have in it, rated in pounds per square inch, or PSI. Since some cars have different rear tires compared to the front, you'll see front and rear ratings. If you have a spare tire, that PSI rating will be listed for that as well.

It's important to note that air pressure PSI ratings are for "cold tires". That means when your tire is at ambient (aka: room) temperature. If you've driven your car recently the tires will be warm and the air pressures will be different than when they're cold. So always check and fill tires when the car has been sitting for at least a few hours.

Step 2: Prepare The Tire


Every tire will have a tube protruding from the tire, this is called the valve stem. Each valve stem will have a cap on it called a dust cap. Remove each dust cap and set it aside in a safe place. Righty tighty / Lefty loosey!

Step 3: Check Existing Pressure


For each tire on your car, as well as your spare tire, use a tire pressure gauge to check the current tire pressure rating. Don't have a tire pressure gauge? You need one and it should remain in your car at all times!

You can get some cheapy pencil-style gauges for under $10 but they're not the most accurate. Slightly better might be the digitial gauges but they're not all that great and the batteries tend to go dead when you need it the most. My advice is to get a high quality dial gauge like this one for around $20.


To check the pressure, just hold the end of the gauge onto the tire until the gauge registers the number. Hold the end perpendicular to the valve stem. It's normal to hear a tiny bit of air escape as you push it on, but as you hold the gauge on no further air should be escaping. If you hear air leaking out still, you're not holding the gauge straight on or have a cheap gauge!

Step 4: Fill The Tire


Filling the tire is just as easy as checking it. You'll need a source of compressed air, something many gas stations offer for a few coins. The better option, which avoids you warming the tires on a gas station run, is an inexpensive portable air compression like this one. It's money well spent.

The key to filling tires is to not over inflate them. Press the air compressor line on the tire firmly so you're not leaking air out. Hold it for a few seconds and take a pressure reading with your gauge again. Repeat that until you're at the recommended PSI for your tires.

If you put in an extra pound or two (1-2 PSI too much) it's not really a major issue, but if you go too far over the recommended rating then you'll want to let some air out. You can do this with your gauge. Some have a button that will bleed air out while you hold the gauge on. If you don't have that button just gently press the gauge on the valve stem and let some air escape. Check the pressure again when you're done to make sure you didn't let out too much. When you're done, put the dust cap back on the valve stem.

Drive On!

You did it, you successfully checked your tire pressures and filled them to the recommended and safe levels. You're car will drive better, get better gas mileage, and you'll be safer on the road.

Green Dust Caps?

In most older vehicles, the dust cap on your valve will be black, gray, or maybe you have a fancy metal one. In some newer cars you may seen a green dust cap. What do these different colors mean?

A green dust cap is special, any other color is not. Meaning, if you don't have green just fill your tires with air as described above. On the other hand, if you have green caps you have a choice to make. Green caps indicate that your tires are filled with nitrogen rather than simple compressed air. Nitrogen is harmless, and makes up around 80% of our atmosphere.

Why use nitrogen? It reduces the rate at which tires naturally deflate and eliminates moisture inside the tire.

So you now have a choice to make. Assuming you bought the car new and know it's only been serviced with nitrogen you can keep putting nitrogen in. This usually means your dealer or a tire shop has to fill them which isn't always convenient.

Or, you just fill them with regular compressed air. It's really your choice but if you're concerned you can chat with your dealer to make sure it won't void any warranty or cause issues.
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