Why Does My Car Tire Keep Going Flat?

Reviewed by

Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Written by CarParts.com Research Team - Updated on June 17th, 2024

Reading Time: 5 minutes
Summary
  • Tires deflate when their air pressure drops, eventually going flat if uninflated.
  • Tires go flat due to various reasons, such as sun exposure, extreme temperatures, and underuse, which make them lose air pressure rapidly.
  • They can also go flat due to damage, leaky tire beads, and malfunctioning valve stems.

Most drivers will deal with a flat tire at some point in their lives. It’s a painfully common problem, especially in wintertime when temperatures drop and regular tires can’t put up with the weather. Tires can also deflate when they’re not in use and kept safe in a garage.

The best way to prevent getting a flat tire is to know the things that cause it and avoid them.

What Causes Tires to Go Flat?

Tires go flat due to various reasons though it all boils down to air pressure decreasing to the point that the tire deflates. If your tire goes flat or feels softer or weaker than usual, it’s because it doesn’t have enough air pressure.

A tire that only has 50% of the recommended tire pressure can still look like it has plenty of air (see illustration). | Image Source: Richard McCuistian

Air pressure constantly decreases in tires at a rate of approximately 1-3 psi every month. but this process can also accelerate due to external factors. For example, when a tire gets punctured, the air rapidly escapes the tire, causing the tire to deflate quickly.

Here are some of the many reasons why tires go flat.

Age and Damage

As mentioned previously, the air pressure of a tire decreases by 1-3 psi every month, meaning a tire lasts an average of six months before it’s time to inflate again. As such, tires lose air whether they’re used or not. This is one of the reasons for the NHTSA requirement that all vehicles had to have tire pressure monitoring systems (TPMS) after September 1, 2007.

Not driving your vehicle often can also cause its tires to degrade and become brittle, especially if it’s exposed to the elements. This accelerates air leaks, causing tires to go flat.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Tires that are more than 6 years old are out of warranty. Most manufacturers say tires aren’t safe after 10 years even if they still look new.

Gravel, branches, rocks, nails, screws, and other road debris can damage tires as well.If the damage is deep enough, the pressure inside the tire becomes equal to atmospheric pressure, which means the tire will be flat.

Sun Exposure

Sunlight has harmful ultraviolet rays, which can make tires weak and brittle after prolonged exposure. This makes them more likely to rupture, crack, and get punctures from road debris.

Moreover, prolonged exposure to sunlight means being exposed to high temperatures, which causes the air inside a tire to expand. That’s bad for already-weakened tires because too much air can make them burst and become unusable.

To reduce sun damage on your tires, avoid parking your vehicle in areas without shade during sunny days.

Extreme Temperatures

High temperatures are bad for tire air pressure, and the other side of the spectrum is no better. Cold weather causes the air inside tires to contract, resulting in a drop in air pressure and rapid deflation.

Because of this, experts recommend using winter tires in low-temperature conditions because they’re specially designed to withstand the cold. They can also maintain good traction when driving over snowy and slippery surfaces.

Leaky Tire Bead

The tire bead is the part of the tire that sits at the edge, resting on the rim. If it’s not secure, air can out of it every now and then.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Steel rims can rust around the bead, and aluminium rims can cavitate at the bead due to oxidation.

One way to test if your tire has a leaky tire bead is to lather the bead with soapy water. If the liquid bubbles, there’s air leaking from the tire bead. If you have a large enough water tank, you can submerge the tire and look for air bubbles.

Malfunctioning Valve Stem

Valve stems let air in and out of your tires. If it’s damaged or faulty, air can leak out, causing tires to lose air pressure and become flat. This problem also happens when a valve stem gets clogged with dirt, gunk, and other debris or when the Shrader valve seal is compromised with time.

Underusing the Tires

Last but not least, letting your daily driver gather dust in your garage does more harm than good for your tires.

While not driving will save your tires from wear and tear, the lack of use can affect their structural integrity and accelerate deflation. Tires need to be used to keep the chemicals in the rubber effective.

Fortunately, driving your vehicle at least once or twice a week can prevent your tires from drying up and becoming cracked and brittle.

If you have a large enough water tank, you can submerge the tire and look for air bubbles.

Richard McCuistian, ASE Certified Master Automobile Technician

How to Prevent Tires From Going Flat

While it’s good to know what causes tires to go flat, it’s better to know how to prevent your tires from going flat in the first place. Here are some of the things you can do to prevent tire deflation.

Frequently Asked Questions

Why does my tire keep going flat in cold weather?

As mentioned previously, low temperatures reduce tire air pressure because they make the air contract. The tire can go flat when the air pressure decreases enough.

Why does my back tire keep going flat?

If a specific tire keeps going flat while the others stay in good condition, there’s a good chance a leaky tire bead is responsible. To fix this, find the source of the leak and address it. If the leak is too extensive, it might be better to replace the tire.

Why do tires go flat when not used?

When tires are seldom used, their rubber tends to oxidize, which hardens or softens them, depending on the tire’s structure. Either way, this reduces the rubber’s flexibility, increasing the risk of cracks and other forms of damage that can cause air to leak.

Where to Get High-Quality Tires for Your Vehicle

While patching tires is a good way to preserve your wheels, there are times when it’s best to get a replacement instead. When this happens, it’s best to look for high-quality tires that are sure to last. Lucky for you, CarParts.com has you covered.

We have a great selection of tires, and other parts and accessories, carefully handpicked by industry professionals. You can count on us to provide OE-grade parts for your ride.

Enter your car’s specifications into our vehicle selector to start shopping. Narrow down the results according to your personal preferences using our search filters, and check out securely in a matter of minutes.

All our products come with lifetime replacement and low-price guarantees to help you get the best value for your money.

Shop now at CarParts.com, and we’ll deliver your order straight to your doorstep in as fast as two business days.

About The Authors
Reviewed By Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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CarParts.com Research Team and Richard McCuistian, ASE Certified Master Automobile Technician