How To Check Tire Pressure: Everything You Need To Know (2024)

When something is seriously wrong with your car, you may hear weird noises or see flashing lights, and in some cases, it might not even start. But when there's something wrong with your tires, there's a chance you won't know until you experience a catastrophic tire blowout or other dangerous event. Being a responsible and safe car owner means checking your tire pressure regularly, but it's often something that's out of sight, out of mind.

AAA Roadside Assistance has helped thousands of drivers stranded with tire issues over the last 100 years. Learn everything you need to know about how to check your tire pressure so you can stay safe on the road.

Table of Contents

• How To Check Tire Pressure
• How To Adjust Tire Pressure
• Why Tire Pressure Matters
• What Should My Tire Pressure Be?
• What Impacts Tire Pressure?
• When Should I Check Tire Pressure?
• FAQ
• Experience a Tire Problem on the Road? AAA Can Help

How To Check Tire Pressure

Fortunately, you don't have to be a mechanic to check your tire pressure. Here are some ways you can check it on your own.

Use a Tire Pressure Gauge

A tire gauge is the most accurate method for checking your tire pressure, especially if you have your own. While you can check your tire pressure at a gas station air pump, the pressure gauges may be damaged due to weather exposure and overuse.

There are three types of tire pressure gauges:

• Stick pressure gauge: This type of gauge is roughly the size of a pencil and has a rod that slides out of the valve when you press the gauge to the valve stem. It is relatively cheap and easy to store in your glove box, but reading the stick can be tricky, making it harder to read than other gauges.
• Dial pressure gauge: This gauge is used the same way as the stick pressure gauge, but its readout resembles a blood pressure cuff, with the pounds per square inch (psi) listed around the face and a hand that points to the appropriate pressure. It's easier to read than the stick pressure gauge, but it's harder to store in your car and more expensive.
• Digital pressure gauge: This gauge has an LCD screen that displays the tire pressure instead of the stick or dial. It's the most accurate except when the batteries wear down.

To check your tire pressure with a tire pressure gauge, wait for the tire to cool (usually about three hours after you've been on the road), then remove the valve stem cap and press the gauge to the stem.

Without a Gauge

If you don't have a gauge, there are a few things you can do in a pinch, although most of them will only identify significant problems:

• Look at the wheels. An underinflated tire will appear flat where it meets the road.
• Feel the wheels. If the tire is soft when you press on it, it probably has low pressure and needs more air.
• Load weight into the vehicle. If the tire sags when you add more weight to the car, that could indicate the tire is underinflated.
• Look for handling changes. If your ride is bumpier than usual or you start noticing steering noises or difficult steering, your tire pressure may be off.
• Take the vehicle to a mechanic. This is the most accurate way to check your tire pressure without a tire gauge. Your mechanic will be able to check your tire pressure for you.

How To Adjust Tire Pressure

Adjusting tire pressure isn't complicated once you know what you're doing. You can do it at home if you have a tire pressure gauge and an air pump or air compressor. If not, drive to a gas station with an air service station, but you may have to pay anywhere from 50 cents to $1 for air.

How To Fix Low Tire Pressure

When your tire pressure is low, you need to add more air to your tires.

1. If using a stationary air pump at a gas station, pull up as close as possible so the hose will stretch to all four tires.
2. Find the recommended tire pressure on the sticker on your driver's side door or in your owner's manual.
3. Remove the valve stem cap from the tire. Set it somewhere safe where you won't lose it, like on top of the tire or in your pocket.
4. Use the tire pressure gauge to check the current tire pressure.
5. Attach the air pump hose to the valve stem.
6. Turn on the air pump.
7. Turn off the air pump. (Some pumps may fill to preset psi, in which case you can skip to step 9, while others you will have to stop manually.)
8. Remove the air pump hose from the valve stem and use your tire gauge to check the tire pressure. Repeat steps 5-8 as needed until you get to your tire's recommended pressure.
9. Replace the valve stem cap.
10. Repeat for the next tire until you've checked all four tires on your vehicle.
11. Don't forget to check the tire pressure of your spare tire (if you have one)!

If your tires are hot because you had to drive to the air pump at the gas station, your tire pressure reading will not be accurate. However, you probably don't want to sit at the gas station for three hours waiting for your tires to cool.

Instead, fill the tire to four psi above the minimum recommended pressure. The next morning, or after the tires have had time to cool for at least three hours, release tire pressure until you get to the recommended pressure using the steps in the next section.

How To Fix High Tire Pressure

When your tire pressure is high, you need to release air from your tires.

1. Find the recommended tire pressure on the sticker on your driver's side door or in your owner's manual.
2. Remove the valve stem cap from the tire. Set it aside so that you won't lose it.
3. Use your tire pressure gauge to check the current tire pressure.
4. Depress the center valve pin (brass needle in the middle of the valve stem) with a tool, tire gauge or your fingernail.
5. Use your tire pressure gauge to recheck the tire pressure. If your tire is still overinflated, repeat step 4.
6. Replace the valve stem cap.

Why Tire Pressure Matters

Your tires are the only part of your vehicle that touches the road, so failing to maintain the proper tire pressure can impact every aspect of your car.

Decreases Your Car's Fuel Efficiency

When your tires are underinflated, more surface area of the tire is in contact with the road. While this sounds like a good thing, it increases friction, which means your car requires more energy to move the wheels. As a result, an underinflated tire will decrease your car's fuel efficiency. According to the U.S. Department of Energy, tires that are 20 percent underinflated will increase your car's fuel usage by 10 percent. Overinflated tires don't negatively impact gas mileage.

Shortens a Tire's Life Span

When a tire is properly inflated, it wears evenly. However, overinflated tires wear more quickly in the center of the tire, while underinflated tires wear more rapidly on the edges of the tire.

When tires don't experience even wear and tear, their life span decreases because they become unsafe, potentially causing issues with your suspension and steering systems.

Can Cause Dangerous Tire Failure

When your car is in motion, the air within your tires heats up from the friction with the road. As it heats, it increases the tire pressure. If your tire is overinflated, the hot air may begin escaping from the tire, leaving you stranded with a flat tire.

If your tire is underinflated, the sides of the tire may come into contact with the roadway. The sides are not intended to touch the road, so they are thinner and therefore weaker. That weak spot may give way while you're driving, causing a tire blowout, which can cause you to lose control of the car and crash.

Interferes With Other Systems

Your tires interact with several other systems in your vehicle, so if your tire pressure is off, you may see issues with the following other systems:

• Suspension: Overinflated tires may cause your car to bounce more than it normally would because less of the tire is in contact with the road.
• Steering: Underinflated tires have a sluggish response time because there's too much friction on the tire.
• Braking: if your tires are underinflated, the brakes may require more force to bring you to a stop.

What Should My Tire Pressure Be?

Most recommended tire pressures fall between 30 and 35 psi, although it varies by car make and model. Each vehicle is different, and front and rear tires on the same vehicle often have different recommended tire pressures.

To find your car's recommended tire pressure:

• Check your vehicle's tire placard, a sticker usually located on the driver's side door frame or the glove box.
• Look in your car's owner's manual.
• Ask your trusted mechanic.

You'll probably see a psi indicated on your tire, but this is not a recommended tire pressure; this is the maximum tire pressure your tire can withstand. Do not fill your tires with this psi, as you'll likely experience a catastrophic tire problem.

What Impacts Tire Pressure?

Tire pressure fluctuates for various reasons, which is why you should check your tire pressure frequently.

Weather

Weather is the biggest culprit for tire pressure fluctuations. Research shows that a tire's pressure can decrease 1-2 psi for every 10-degree drop in temperature, or increase 1-2 psi per every 10-degree increase.

Permeation

Tires can lose up to 3 psi per month naturally through permeation. Also called osmosis, permeation is when air escapes through the rubber.

Altitude

Higher altitudes have lower air pressure, which is why some people experience ear popping during flight takeoffs or landings. That same shift in altitude impacts your vehicle's tire pressure. Tire pressure will increase 2-3 psi for every 5,000 feet in altitude increase. It will decrease 2-3 psi for every 5,000 feet you drop in altitude.

Because ideal tire pressures are a range, you can drive safely through the mountains without stopping to check your tire pressure. Before you go somewhere with a higher altitude, release some tire pressure until you are at the lower end of the range to allow the air pressure to increase safely while you are at a higher altitude.

Road Hazards

Tires are made of rubber because it is stiff enough to keep the tire's shape but flexible enough to adapt to a road's surface for a safe drive.

However, that flexibility means a road hazard can impact your tire pressure. Running over a nail or screw may poke a hole in the rubber, causing a slow leak. Potholes and bumps can put extra force on a tire or break down the rubber over time, increasing the rate of permeation.

Most likely, road hazards contribute to slow and steady pressure changes, although there have been occasions where a road hazard has led to an immediate flat tire, requiring roadside assistance.

When Should I Check Tire Pressure?

Most modern cars are equipped with a tire pressure monitoring system (TPMS), which automatically monitors your tire pressure. An indicator light , usually a U shape with an exclamation mark inside it , will light up on your dashboard near the check engine light when your tires are under or overinflated. However, the indicator light will only come on when there is a significant issue, so it's best to monitor the pressure yourself.

Mechanics recommend checking the pressure of your tires (including your spare) at least once a month or any time you experience the following:

• Your TPMS indicator light comes on
• A substantial shift in temperature
• A change in seasons
• Lower gas mileage
• Sluggish response time
• Change in altitude
• Driving over rough roads

Your mechanic will also check your tire pressure whenever you take your car in for regular maintenance.

FAQ

Below you'll find answers to a few frequently asked questions about tire pressure.

How Long Can You Drive With Low Tire Pressure?

If you know you have low tire pressure, add air to your tires as soon as possible to avoid a potential tire blowout.However, that may not always be possible. In ideal conditions, you can drive a short distance safely, but the more time you drive on it, the more likely a tire failure will occur.

How Do You Reset the Tire Pressure Light?

The tire pressure light should turn off automatically once you adjust the tire pressure. If it doesn't, you can reset the tire pressure light with any of the following methods:

1. Drive your car on the highway for roughly 10 minutes.
2. Start your vehicle and let it run for about 20 minutes.
3. If your vehicle has a TPMS reset button, turn the key in the ignition so the radio and lights work but the car isn't on. Then hold the TPMS reset button until the icon flashes three times.

Should I Replace Tire Pressure Monitors When I Get New Tires?

Like any other system in your car, the TPMS needs regular maintenance to keep it functioning correctly. When you have your tires rotated or you have new ones installed, the mechanic will service the system and test it. If they notice any issues, they'll recommend replacing the system.

Fortunately, most tire pressure monitoring systems last for about a decade without a problem as long as they are regularly serviced. If you need to replace your TPMS, the cost will vary based on the make and model of your car.

Experience a Tire Problem on the Road? AAA Can Help

Even with regular tire pressure checks, it's possible you'll experience a tire blowout or a flat tire at some point in your driving career. Sign up for a AAA membership today so you can join the millions of members who are prepared for such an event. AAA Roadside Assistance will come to you to install your spare tire or tow your vehicle to an approved facility if the spare tire is unsafe.

AAA does more than help with tires , our roadside assistance team can also help you jump your car, and our AAA-approved repair facilitators can help determine whether you need a new alternator or a new battery.