By Anthony Santiago - Editor-in-Chief

September 15, 2022
how to refill car tires

When was the last time you checked your car tire pressure? Do you even remember how to do it? We will cover in this article, the steps on how to refill car tires.

It's very common that the (TPMS) tire pressure warning light will pop up if the ambient temperature drops as the seasons change and lose pressure over time. Most likely your car was beeping with the low tire pressure indicator light on the dash. What should you do and what is the best way to fill your tires up with air? 

Typically the PSI that triggers the warning light is 24 PSI. If your air pressure drops to this range then the dash will trigger this light. This is very common in cold temperatures.

Depending on the monitoring system in your vehicle, you might be able to determine the pressure or to see which tire is low. If you have a basic system then you will have to check each tire separately since it does not report exactly which tire it is.

The good thing about modern TPMS is that you can easily maintain the proper pressure for better fuel economy and reduced tire wear. And as we've seen from recent events, it's important to get your car tires properly inflated.

I'm going to tell you everything you need to know about how to refill your tires, portable solutions and the ins and outs of nitrogen air.

Steps to Pump Up Your Car Tires with Air

Refilling your car tires is fairly easy. Just be aware that you will be bending over or squatting to reach for the tire valve stem in order to refill the air. In order to have an accurate reading, you will want to check your tires when they are cold (preferably overnight) or cool the touch, after you have been driving.

When checking your tires, always try to do so when they're cold. If you do so, the pressure readings won't be completely accurate because the tire heats up during the ride, which causes the pressure to increase.

1. Check Car Manual or Sticker for the Recommended Tire Pressure

You can check your owner's manual or the driver's door pillar for the official numbers for the proper tire pressure for your vehicle. Depending on the load and the number of passengers, the pressure can vary.

2. Get a Tire Gauge

A tire gauge will help you measure the actual pressure in your tire. You can not visually determine if the tire pressure is low or not just based on looking at the sidewall. Most tires today have some flex where the tire meets the road and it may look low but it might be ok.

Tire gauges come in different designs. There is a pencil side or the gauge face style. I have used both and both are easy to use. I prefer the dial gauge because it's easier to read.

3. Remove the Valve Cap

Look at your wheel and locate the rubber stem that is sticking out of the face of the wheel. There will be a valve cover that you will remove in order to fit the tire gauge on. Be careful to not lose the valve cap as it is used to protect the valve stem from water and the elements.

If your valve cap is GREEN, then at one point your tires were filled with nitrogen. You can mix nitrogen and regular air together. Nitrogen is used sometimes since it is less likely to leak out since the nitrogen molecules are larger in size than oxygen. However, nitrogen is still a gas and is sensitive to temperature fluctuations, just like regular air.

If you lose your valve caps, you can easily purchase new ones for a few dollars.

4. Place the Tire Gauge on the Valve Stem

There should be some pressure in the tire. When you place the tire gauge on the valve, some air will naturally leak. Continue to press the tire gauge firmly until the air stops leaking and the pressure is taken.

For pencil style tire gauges, you can remove and the measurement will be recorded. Otherwise, the tire gauge with dial face will need to be read while placed on the valve stem.

However, if you have a flat tire, then it will read with 0 PSI and the gauge will not move.

5. Keep a Mental Note of the Pressure Reading

If the pressure is under 30 PSI, this might be the tire that needs to be filled up. Before you start filling up the tires with air, it would be good to get an overall picture of all the tire pressures on all four corners.

Move to each corner and check the tire pressure readings.

6. Get Ready to Fill the Tires with Air

The reason we have not filled the tires yet is because we want to ensure we have enough time to move from tire to tire as the pump at gas stations runs for only 3 minutes. You don't want to waste time checking the pressure and removing the valve stems.

When you are ready, remove the hose from the air pump at the gas station and check to make sure it will reach all of the tires sufficiently.

Start the air pump and fill the tire that had the lowest pressure. It may take a while for this to pump but most gas station pumps are pressurized and will fill the tires quickly.

DO NOT OVERFILL the tires. I would fill the tires MAX of 40 PSI - 42 PSI or to the desired optimal pressure per the recommended rating. You will be able to adjust the pressure to the correct number after the air pump stops.

You just want to make sure that all tires have enough pressure to be adjusted.

7. After All Your Tires are Filled. Check your pressure.

When your time is up with the air pump, the machine will automatically shut off. Return the air hose and coil it back properly on the machine.

Now, double check the tire pressure using your tire pressure gauge.

If the air pressure is too high, then use the nub on the tire gauge to remove some air. You should remove air little by little and recheck the pressure. Continue until you have reached the proper tire inflation pressure.

Replace the valve cap on the air valve and move on to the next tire.

Remember, don’t over inflate your vehicle’s tires. This could damage your car’s suspension system and cause it to lose traction. Overinflating tires can also lead to blowouts and punctures.

The Best Time to Check Your Car's Tire Pressure

Cold weather causes tires to lose air faster than warm temperatures do. As a result, you should check your tire pressure more frequently during cold months. In fact, it’s recommended to check your tire pressure once per month.

If you notice a significant drop in pressure over a short period of time, you should contact your local auto repair shop immediately. This might be a sign that you have an air leak. This might be caused by a bad valve stem, nail or bad tire bead. Your tire shop will be able to determine the best course of action.

How to Refill Car Tires - portable air pump

Should You Buy a Portable Air Pump?

Yes, based on my experience it's a small investment to have peace of mind. Most tire air machines can cost anywhere from $1.00 to $2.00 to fill your tires. If you multiply this 4 times a year, you can easily see this adding up if you have multiple cars.

You don't need a very expensive one. I purchased a simple one on Amazon for around $35 (back in 2020). This has helped keep my tires pumped up and helped a few family members with filling tires as well. Look for air pumps that have long hoses and power cables so you have enough slack to move from front to back easily.

The good thing about this pump is that it has an auto shutoff once the set air pressure is reached. It has been used at least a dozen times already.

Is Nitrogen Better than Regular Air?

Nitrogen makes up about 5% of air. If you fill your car tires with it, you'll increase the pressure inside the tire by about 20%. This increases the amount of force exerted on the tread area of the tire, making it harder for dirt and debris to penetrate the rubber. In theory, this could help prevent flats.

As mentioned earlier, Nitrogen is less likely to escape from the rubber since its molecules are larger than oxygen.

The Reason Nitrogen Works Well for Tires

Nitrogen works well when it comes to tires. Why? Because nitrogen-filled tires stay properly inflated without causing damage to the rubber. This makes them safer and reduces wear.

Nitrogen Benefits

Air and water are both great insulators against heat, but nitrogen is much better. Air heats up when it gets hot, while water evaporates into steam. Nitrogen doesn't change phase like either of those elements do. Instead, you don't lose energy to evaporation. And because it's a dry gas, there's no moisture to attract oxygen and oxidize rubber.

Final Thoughts on Tire Air Pressure

Gas station air pumps are expensive. Plus, if you don't have coins it might make it difficult to pay for the machine. Filling tires with air can be oftentimes overlooked but it's very important to maintain the right pressure for better performance and fuel economy.

Also check your spare tire each year so you are not caught off guard when tire failure happens. You don't want your spare to be one of your under-inflated tires in an emergency.

There are some shops that still offer free air. I know that Costco Centers with Tire Department offers free air to customers. The trick is knowing which tire shops offer free refills and which ones charge extra fees.

Fortunately, we covered plenty of easy ways to help ensure that your car's tire pressure stays where it belongs. First, check your owner's manual for instructions on how to properly inflate your tires. Follow the steps detailed in this article.

Finally, fill your tires to the recommended level whenever possible. Good luck and safe driving.

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Anthony Santiago - Editor-in-Chief

About the author

I am a passionate car enthusiast who likes to help people save money and avoid headaches when it comes to cars. I believe that everyone can find the right car at the right price. I share my tips and experience so you can learn quickly and maximize your next SUV, truck or car purchase.

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