Why Your Tire Pressure Keeps Fluctuating and What It Could Mean

As a certified ASE and General Motors Master Technician, vocational instructor and consumer, I have almost 60 years working in and around the automotive industry. One item about cars that is always a topic of discussion is tires. Everything from handling and performance, tread design, noise, mileage, braking, vibrations, abnormal wear, damage, of course, to even making repairs. However, in my experience, the main issue drivers have with tires: maintenance, especially why air pressure keeps changing.

With the advent of modern Tire Pressure Monitoring Systems (TPMS) and the dreaded Tire Pressure Warning Light, concerns have grown exponentially. Before panicking, let’s read what the experts have to say about why tire air pressure changes and what to look for.

Normal Tire Pressure Fluctuations

Tire pressure fluctuation is nothing out of the ordinary. Changes in temperature are the most common reason air pressure fluctuates. “The air’s response to temperature causes it to expand and contract, and your tires can lose around one pound per square inch (PSI) for every 10 degree drop in temperature, and the reason why drivers get a low tire pressure warning light during the colder months,” said Fang (Bob) Shusheng, Owner and CEO of Nilight, manufacturer of high performance and off-road automotive equipment.

“Air pressure increases as tires warm up while driving and temperatures rise throughout the day,” said Jim DeLeo of  Hunter Engineering. “Conversely, as your tires sit overnight and cool down, air pressure can drop.

“Temperature fluctuations should affect all four tires equally, with pressures normally rising once the tires heat up,” added Shusheng.

Common Causes of Ongoing Fluctuations

Large temperature swings, especially in colder climates, are the most common cause of tire pressure fluctuations. “Cold can cause a tire to contract slightly,” DeLeo added, noting this can reduce a tire’s internal volume, resulting in lower tire pressure until the tires warm back up.

When Fluctuations Are a Problem

While small tire air pressure fluctuations are totally normal and should be expected, other issues to look out for include:

• One tire consistently loses more air pressure than the others, and air pressure drops within days of refilling with air.
• The TPMS light constantly comes on for the same wheel.
• Air pressure drops even when temperatures remain relatively stable

What to Do About It

DeLeo explained, “Always set your tire pressure [first thing in the morning] when the tires are cold.” Use the Tire and Load Information placard—usually located on the driver’s door jamb or owner’s manual—specifications, not the maximum air pressure found on the sidewall. “Check pressures at least one time a month, and more often during the winter,” said DeLeo.

If one or more tires keep losing air pressure, have your tire checked for:

• Punctures from a nail, road debris or even a toothpick (yes, I saw this once!) will cause a tire to keep losing air pressure.
• Wheel bead corrosion from the build-up of water or moisture inside the tire. This is usually caused by poorly installed wheel weights, a bent wheel or tire damage.
• Wheel porosity (usually undetectable by eye) is microscopic fissures triggered from corrosion in an aluminum or composite wheel that causes very slow air pressure loss.
• Tire dry rot from ultraviolet (UV) rays can weaken and crack rubber, resulting in air slowly leaking through tiny fractures commonly found on the sidewall or tread area.
• Valve stem leaks can be checked using a soapy water solution. Never overtighten the valve stem on a Schrader valve, especially in TPMS valve stems.
• Ensure all wheels have valve stem caps installed.
• You can try replacing “air” with nitrogen.

Safety and Fuel Economy Impact

If you’ve ever read my Family Handyman articles, you know that tires, brakes, steering and suspension systems are the most critical safety systems on our cars. Underinflated or overinflated tires have less tread area contacting the pavement. Remember, the part of the tire that touches the road is called the contact patch or footprint and isn’t much larger than the palm of your hand.

That is why maintaining correct tire pressure is vital. ASE and Ford Master Technician Jon Stull said, “Overinflating tires will not stop air pressure loss from temperature changes.”

“Low pressure can not only make tires look deflated, but can affect the way a vehicle drives,” Shusheng added. “They might make steering feel sluggish, increase braking distance and create more rolling resistance, which can contribute to tires wearing out faster.”

Think about the extra effort needed to pedal a bicycle with underinflated tires. The engine having to work harder will use more fuel, lowering fuel economy as well as increasing overall engine wear and tear. “Overinflation reduces traction, causes the tire to become stiff and makes it prone to blowouts. The center tread area wears faster than the rest of the tire tread,” said Shusheng.

In addition, overinflated or underinflated tires negatively affect braking, handling, and cornering, especially on wet or icy roads.

FAQ

Can I drive with the tire pressure warning light on?

Yes, but don’t. “A vehicle’s low air pressure warning light turning on gives drivers an important warning that their tires need immediate attention, and should not be ignored,” said Shusheng. It means a tire is significantly underinflated and you could be on the verge of a flat tire, or worse, a blowout from overheated tires.

As DeLeo explained, “On a really cold night, a considerable drop in PSI isn’t unusual.” That much change can be just enough to turn on the TMPS light, yet as the tires warm up, pressure can increase two to six PSI after 25 minutes of driving, or just enough to turn the TPMS light off. Other reasons the TMPS light comes on include:

• A damaged, corroded or defective TMPS sensor.
• A weak TMPS sensor battery.
• One or more sensors need to be recalibrated after a dead battery.
• Rotating or installing new tires.
• Mismatched tires.
• Worn wheel bearing.

How often should I check my tire pressure?

Avoiding tire problems starts with you, the vehicle driver. Performing these basic maintenance steps including:

• Check tire pressure every month, more often in winter.
• Visually inspect tires once a week.
• Rotate and balance tires and wheels every 5,000 to 8,000 miles and have the pros perform a wheel alignment once a year.

About the Experts

Jon Stull has been an ASE Master Technician for 28 years. (Email correspondence Feb 6, 2026)

Jim DeLeo has been in the automotive repair industry for over 40 years and held positions as an ASE master technician, shop foreman and service manager, and is now Northeast Division Manager for Hunter Engineering Company. (Email correspondence Feb 6, 2026)

Bob Shusheng got his start in business, by selling a variety of products on eBay as well as a variety of products, including Nilight automotive equipment and accessories, to sell on Amazon. As sales of Nilight light bars started taking off, Bob decided to fully expanded the Nilight car and truck accessory parts catalog and starting his own factory so he could control part quality, features and value. (Email correspondence Feb 10, 2026)

Resources

AutoZone: “Why Does Tire Pressure Drop in Cold Weather?” (Feb 2026)

Bridgestone: “What is TPMS and How Does it Work?” (Feb 2026)

Consumer Reports: “Why Does Your Tire Pressure Drop in the Cold?” (Oct 10, 2025)

Kelly Blue Book “What Does ‘TPMS’ Mean on a Car?” (Apr 12, 2024)

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