How To Tell If a Tire Is Flat Or Just Needs Air

As an amazon associate motorhills.com earns from qualifying purchases.
Close up of a flat tire

We’ve all been there. You start your car in the morning, and you’re greeted with a “Low Tire Pressure” warning. The car isn’t smart enough to tell you if you have a flat or the tire just needs air.

If it’s the same tire over and over, then there’s probably a puncture. If multiple tires are low, the weather is starting to get colder, and the pressure normalizes after driving to work, then it’s likely that your tires just need some extra air.

To help out, I put together this guide. I’ll walk you through the troubleshooting process, give you some important questions to ask yourself, and teach you more about how your tire works. By the end, you’ll be able to tell if your tire is flat or just needs air.

Parts of a Tire

Before getting into the specifics, I want to talk about how your tire works. Each tire is made up of the same parts:

The tread. This is the textured rubber on the outer face of your tire. With a healthy tire, the tread is the only thing that comes in contact with the road. The different grooves help your tire get traction on the surface your car is driving on.

A sidewall. The sidewall is the rubber part that goes vertically on your tire. This gives your tires some added lateral strength and keeps everything together.

Close up of the car tire sidewall with the size and specification

Plies. These are layers of different fabrics inside of your tire. When air is put into your car, it gets pressurized between these plies.

Air valve. There’s a little nub that sticks out of each tire. This is the air valve where you pump air into the tire. It has a hose that feeds into the center of your tire between plies. As you add air, you’re pressurizing the inside of your tire and expanding the rubber. This is easier to see on a bike tire which is smaller and requires less air.

The Importance of Air in Your Tires

The importance of this guide revolves around how important air is inside of your car tires. There’s a reason why alarms start going off when your tires have too little or too much pressure.

As I mentioned, adding air to your tires increases the pressure. When the tire is pressurized, the rubber will expand outwards. With too much pressure, there’s too much expansion and the opposite is true with too little pressure.

Tires are manufactured for their tread to sit on the road a specific way. This optimizes how much grip your tires have without ruining your fuel-efficiency or car’s performance.

Checking the car tire pressure with an air pressure gauge

Since pressure determines how the rubber sits, it also changes how the tread acts on the road. If you have way too much pressure, then your tread will have an arc to it which leads to a worsened traction.

With too little pressure, your tread falls flat and some of your sidewalls could be compromised while you drive.

The goal is to keep your tires within the golden pressure range at all times. This is the PSI value posted on your doorframe.

If your air pressure is too low or high, you might notice:

  • Worsened performance
  • Poor traction as you take turns too fast
  • The road feels bumpier and louder
  • Poorer fuel efficiency
  • It takes you longer to come to a complete stop

Why Do Tires Go Flat?

As a new driver, you might have been taught how to change a flat tire. If not, check out my quick guide to learn for yourself. Either way, we all learned that tires will go flat and that’s a big problem.

A flat tire occurs when something punctures your tire deep enough. If there’s a hole in one of the plies of your tire, then air will be able to escape, and pressure will be lost. Remember, the goal of these plies is to create an air-tight place for pumped-in air to live in your tires.

Bad road with pot holes visible in winter season with trees visible in the background

In general, the tread of your tires is pretty strong. A piece of gravel or hard rock probably isn’t going to puncture your tire deep enough to make it go flat.

Instead, it’s things like nails, screws, and broken glass on the road that can cause a flat tire. All it takes is a deep-enough puncture, and air will start escaping from your tire. Even a tiny hole can flatten your tire over enough time.

Tires Might Need Air Seasonally

If you live in a state where the weather changes noticeably from season to season, you already know that your tires need to be refilled a few times each year.

This is due to the chemistry inside your tires. When temperatures rise, air particles get bigger and more energized. This raises tire pressure and causes your tires to expand. When temperatures drop, the air particles compress, lowering the tire pressure and shrinking your tires.

If you go through a few cycles of hot-to-cold temperatures, then your tires will be underpressurized and they’ll need a quick fill-up.

How to Tell if a Tire is Flat for Just Needs Air

I just explained a little bit about a flat tire and how your tires need air sometimes. Now, let me give you some examples and questions to ask yourself to tell if your tire is flat or just needs air.

Check the Thermostat

The most common reason why your tires need air is because of a change in temperature. If you want to quickly rule out a flat tire, take a look at the calendar and check the temperatures over the past week or so.

Close up of the dash instrument cluster panel with the center LCD showing the cold outside temperature

If they have been fluctuating a lot and it’s near Winter, then it could just be a matter of chemistry tanking your tire pressure.

This will happen when your tires get especially cold.

How Many Tires are Low?

If all four tires are low at the same time, there are two options: either someone really dislikes you and slashed your tires, or the cold air got to your car.

It’s very uncommon for all four tires to pop at once while driving unless you went over a spike strip or did something really bad in your car.

In cases where more than one tire is low, there’s a good chance that you can thank Mother Nature.

Drive Around a Little

The way that I personally tell if a tire is flat or just needs air is to take a quick drive.

If your tire just needs air, your air pressure will go up as you drive. Driving creates friction and heats up the rubber in your tire. As it heats up, the air expands and increases the pressure in your tire. This only happens when the tire is fully sealed and doesn’t have a hole.

Side view of a sedan car driving on a sunny day

If your tire is punctured, then driving around will either have no change on your tire’s PSI or it will lower it even further. As the gas expands, it will just travel out of the puncture even faster.

You’ll only be able to do this if you have a safe route to drive near your house. There’s a chance that you can get stranded if your tire is flat and the air keeps escaping, flattening your tire further — so be careful when you use this method.

Even if you don’t have a flat tire, it doesn’t hurt to add a little bit of air just to get your tire pressure up.

Did You Just Refill this Tire?

If you have a problem tire that you keep refilling, there’s definitely a puncture somewhere. I mentioned it earlier, but even a tiny hole in your tire will break the air-tight nature of your car and allow the PSI to drop. It might not happen in a few hours, but it could take a few days to drop your PSI again.

In this case, it’s technically a flat tire. The only difference is that the hole isn’t big enough to drop your PSI as dramatically as you’d expect. I would still suggest checking out your tire and looking for the puncture. You can either patch the hole or replace the tires.

How Low is the PSI?

With seasonal changes, your tires will only drop a few PSI below the manufacturer’s suggested values. For instance, you might notice that your front tire is 28 PSI and it’s supposed to be 32. Not a huge difference, but you still need to add more air.

Rhino USA Heavy Duty Tire Pressure Gauge (0-60 PSI) – Accurate, Large 2 in.

Rhino USA Heavy Duty Tire Pressure Gauge (0-60 PSI) - Certified ANSI B40.1 Accurate, Large 2 in.
Rhino Tire Pressure Gauge (0-60 PSI)

Based on some other troubleshooting, a small difference like this is likely due to just the weather.

If you look at your tire and you get a reading of 14 PSI, then there’s no way that’s related to temperature. That’s a flat tire. Whenever you have a big drop in PSI like this, then you can rule out anything but a flat tire.

Look for a Puncture

The best way to tell if you have a flat tire is to take off the tire and inspect it. A flat tire has some sort of puncture somewhere.

If you don’t see a puncture, you can use the bubble test. Fill a spray bottle with water and a little dish soap. Shake up the bottle to combine them.

Grab the spray bottle and spritz it all over your tire, focusing on the tread. If there’s an air leak, there will be a lot of bubbles in the area, and you’ll see the motion as the escaping air produces more bubbles.

What if you don’t find the puncture? It doesn’t necessarily mean that there isn’t a puncture, just that it’s so small or in an obscure place.

If It’s a Flat, Fix it

If you determine that the loss of pressure is due to a flat tire, don’t waste any time. If the puncture is anywhere along your tire’s sidewall, there’s a chance the tire will explode. This is called a tire blowout, and it’s devastating for your car.

AUTOWN Tire Repair Kit – 67pcs

AUTOWN Tire Repair Kit - 67pcs
AUTOWN Tire Repair Kit

Any puncture results in a loss of structural integrity in your wheel. Some hole locations are a lot worse than others, but none of them are good. Once you find out you have a puncture, drop everything and fix it.

Conclusion

Now you’re a tire expert. Refer back to this guide if you’re unsure if your tire is flat or just needs air. For more troubleshooting guides, refer to the rest of my blog. I also have a list of products that can help you out, so take a look.

Your subscription could not be saved. Please try again.
Welcome to Motor Hills!

Subscribe now to get access to the top 10 helpful articles!

Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

Leave a Comment