We all know that routine maintenance is important for everything from our computers to our cars. But sometimes, we fall short. One of the most neglected routine car maintenance tasks is to check tire pressures and inflate them as necessary. That’s why newer cars have tire pressure warning lights, or tire pressure monitoring systems (TPMS), that let you know when you have under- or over-inflated tires (when any tire is 25% underinflated).
Older vehicles don’t have this useful warning light. So, don’t wait for a rupture to check or change a tire. Use this guide to learn how to check the pressure (PSI) of your vehicle tires and how to inflate them to the proper air level.
Why should you check your tire pressure?
The number one reason why you should periodically check your tire pressure is SAFETY, but there are monetary and handling reasons as well:
- Longer lasting tires
- Improved handling and control
- Reduced risk of accidents and blow outs
- Better fuel economy
- Reduced carbon footprint
Proper tire pressure (as recommended by the manufacturer) is needed to drive safely and efficiently. According to a 2009 report by the National Highway Traffic Safety Administration:
“…about 28% of light vehicles on our Nation’s roadways run with at least one underinflated tire. Only a few psi difference from vehicle manufacturer’s recommended tire inflation pressure can affect a vehicle’s handling and stopping distance. Poor tire maintenance can increase incidences of blowouts and tread separations. Similarly, underinflation negatively affects fuel economy.”
When your tires are underinflated, the tires get fatter, increasing their surface area. This causes high heat generation and extra resistance that could result in higher fuel costs, blown out tires, tire wear, and loss of control.
If you feel like you’re spending too much at the gas pump, it might be your tires. According to the US Department of Energy:
“You can improve your gas mileage by 0.6% on average—up to 3% in some cases—by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by about 0.2% for every 1 psi drop in the average pressure of all tires.”
In addition to safety and fiscal concerns, keeping your tires properly inflated will also reduce your impact on the environment. When your tires are properly inflated, you’ll pay less for gas, replace your tires less often, and improve your handling and stopping distance. You’ll also feel better knowing that you are emitting less carbon dioxide and other harmful substances into the atmosphere.
What is the right PSI level?
PSI stands for pounds per square inch. The recommended PSI for your vehicle’s tires is determined by the vehicle’s manufacturer and the recommended tire size.
One big question that we get is whether you should follow the recommended PSI level on the tire itself or the recommended PSI level printed in your owner’s manual or on the placard inside of door edge, glove box door, or fuel door.
Do NOT use the max PSI that is printed on the tire sidewall. This is not the recommended PSI level. The pressure amount on the tire is normally the maximum allowed pressure. The correct PSI level is almost always less than what you see printed on the side of the tire. Over-inflation can lead to poor handling and comfort, overheating and blow outs. Over 40 PSI is a dangerous level for most vehicles!
Make sure you always use the recommended PSI as provided in your owner’s manual and don’t go any more than 5 PSI over the recommended level. You should make sure, however, that your tires are appropriate for your vehicle. You can do this by checking the car’s owner’s manual or the placard that is on the inside of the driver-side door, glove box, or fuel door.
Most car tire pressure recommendations range from 30-35 PSI.
How often should I check tire pressure?
A question in many minds is when is the appropriate time and frequency for checking and inflating vehicle tires.
A quick google search will reveal a variety of different opinions and suggestions. Some say that you should check your tire pressure every 2nd visit to the gasoline station, while others say once every 3-6 months is OK.
Most tire and vehicle manufacturers, on the other hand, will say that you should check your tire pressure at least once every month, or every second trip to the gas pump. Your tires will lose around 1 PSI each for every month that goes by.
Unfortunately, not one answer will fit every situation. There are several factors that influence how often you should check your tire pressure, including:
- The weather (hot and cold seasonal changes)
- Driving frequency and distance
- Weight carried or towed
Did you know that for every 10°-drop in temperature, you lose 1 pound of pressure?
If you have a leaky valve or a small puncture, you will lose air pressure much more quickly. This is one more reason why you should frequently check the tire pressure on all of your tires.
Since tire pressure constantly fluctuates, it’s important to check it periodically (at least once a month) and add air as necessary.
How to Check Tire Pressure
Finding out the tire pressure of your tires is incredibly easy. All you need is a pressure gauge (click here for additional items you should have in your vehicle).
Just make sure that you are checking your tires when they are relatively cold. If you check your tire pressure after a long drive, you will get an inaccurate reading since heat will temporarily increase the tire pressure reading.
Unfortunately, not all pressures gauges are created equal. Some are better than others. We recommend shelling out a couple extra bucks for a digital reader. The pop-up, stick-type versions are notoriously inconsistent and unreliable. A reliable gauge will be well worth the investment. Prices range from about $5 for the stick-type and about $30 for the digital and dial-type pressure gauges.
You can also check your tire pressure at most gas stations or auto repair shops. Discount Tire offers free tire pressure checks and inflation.
Here are the steps for checking your tire pressure:
- Check the tire pressure when the tires are cold—first thing in the morning is best. If you’ve been driving for a while, you’ll want to wait several hours before checking your tire pressure.
- Remove the caps to your tires’ air valve (keep them in a safe place, like your pocket).
- Place the tire pressure gauge on the air valve firmly to receive a reading.
- Take the tire pressure reading 1-3 times to get a good average and reduce the risk of anomalies.
- Check the tire pressure gauge reading against the recommended PSI levels recommended by the manufacturer.
- Add some air until your reach the recommended PSI level.
- If the reading is above the recommended PSI level, push down on the air valve to release air. Check the tire pressure again. Release more air if necessary. If you release too much air, you can always add some air back.
It should only take you a couple minutes to check the air pressure of your vehicle’s tires. As soon as you restore tire pressure to the recommended levels, you’ll start experiencing the safety and savings that come with this regular maintenance task.
Watch this video for more information on how to check your tire pressure:
How to Inflate Tires
Here are the steps for adding air to your tires:
- Remove the valve stem caps on all of your tires (keep them in a safe place, like your pocket).
- Use an air pump to fill the tires. Even though it’s possible to fill your tires with a regular old bicycle pump, this is not the most efficient method. Instead, go to your local gas station that has a coin-operated air pump (ask the attendant if you can’t find it). You can also purchase your own automatic air compressor, but it will cost you around $50-$150.
- Inflate your tires when they are cold. If you’ve driven more than a couple miles, you’ll want to wait until they are cold. The best time to refill your tires is first thing in the morning.
- You can usually set the desired PSI level on the machine at the gas station (probably around 30-35 PSI). If your local gas station’s air pump doesn’t have this capability, then you will need to fill up the tire, check the pressure with your gauge, and then add or release air as necessary. Some air pumps will have a built-in tire pressure gauge. Once the PSI level is set, feed coins into the machine until you hear the air coming through. It will be pretty noisy.
- You want to act quickly because you only have a few minutes before the pump turns off. Bring the tip of the air valve to your closest tire valve (or the lowest tire). Hold it firmly against the valve as you listen to the air filling the tire.
- Make sure your vehicle is close enough to the pump so you don’t have to move and pay for another air session.
- Give the pump some time to fill up your tires. If you pre-set the PSI on the machine itself, you will hear a loud beeping noise when the desired PSI is reached. If not, fill up the air for around 5-10 seconds and then check the tire pressure with your pressure gauge. Check the air pressure as you go and refill or release air as necessary.
- If you go over the recommended PSI, you can release air from the tire by depressing the center valve pin with your tire gauge or a similar tool (a fingernail can also do the job). Release the air in small increments and check the pressure as you go.
- When you have reached the desired pressure, make sure you check all your tires again with your pressure gauge. If all is well, you are done adding air.
- Remember those valve caps we told you to keep safe. You’ll want to screw them back on now.
Remember, just one drop in PSI can lower your gas mileage by about 0.2%. For every 3-4 PSI units that your tire is underinflated, you are burning around 1% more fuel.
If your tires are flat, then you probably have a leak. Add air and see if you can drive around without the pressure dropping. If you hear air escaping the tire while you are filling up, then it’s time to replace the tire.
Tip: Learn how to use the air pump properly first. Some automatic air pumps at gas stations have a handle/switch that you need to depress in order for the air to flow. When you let go of the handle, a tire pressure gauge will pop out showing you the tire pressure. At the same time, air will be slowly released. If your air pump has this kind of handle, then you will want to hold down the handle for most of the time, periodically releasing it to check the pressure reading. Consult your own tire pressure gauge for accuracy.
When should I replace my tires?
If you check your tire pressure at least once a month as recommended, you’ll also get a good idea of the general condition of your tires and when you should replace them.
We recommend using the penny test:
- Take a penny and insert the top part of Lincoln’s head (head down) into one of the tire treads. If you can see his entire head, it’s time to replace your tire immediately.
- Consider a replacement soon if only a small part of his head is cut off. You are good to go if Lincoln’s forehead is covered. Use the penny test on a few areas of each tire to get a more accurate reading.
Click here for more car maintenance tips. Click here for car winterization tips.
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