It may be inevitable during a crisp fall or chilly winter morning that you'll turn on your car and an indicator light will light up your dashboard.
You may know exactly what it is and cross your fingers it disappears as you drive a few miles, or the unusual symbol — often a bright yellow or orange cutaway tire with an exclamation point — may be a complete mystery until you check your owner's manual and see it's for the Tire Pressure Monitoring System (TPMS).
Don't worry, you're not alone. The symbol often pops up to indicate low tire pressure, which is "one of the most prevalent issues motorists contend with in the colder months," according to the American Automotive Association, best known as AAA.
While it may be a nuisance to check it out, studies say tires are the most important part of a vehicle — they are the only components that actually touch the ground — and if left underinflated, cause serious safety risks to not only you and your passengers, but others on the road.
Find out the reasons why tire pressure drops in cooler weather, why it's so risky to drive with tires lower than their recommended pressure levels and how you can check your own vehicle's tires to ensure safety for all.
How does cold weather impact tire pressure?
While there are many reasons a tire can lose air — a slow leak by a punctured nail or damage from a pothole — cooler weather or temperature changes as seasons shift are the biggest culprit for tire pressure fluctuations.
For every 10 degrees the temperature drops, tires will drop one to two pounds per square inch of pressure, known as PSI, according to AAA and several other studies. There's a super fascinating law in physics called Gay-Lussac’s Law — you can read about it later — that can explain, in much simpler terms the relationship between temperature and pressure in this scenario: Cold weather causes air in the tires to contract.
It's also important to note that tires also lose about one or two PSI each month due to normal, everyday driving.
How do I check my tires' air pressure?
Basic car maintenance can improve a vehicle's performance and also keep you safe on the road, so it's important to keep your ride in tip-top shape. In addition to easy car care tasks, such as replacing wiper blades or checking oil levels — here's a short video in case you forgot — knowing how to check your tire pressure is important.
You'll need just one item: a tire pressure gauge. For just a few bucks, the classic pen-style tire gauge is easy to throw in the glovebox, or you can purchase a dial or digital tire gauge.
- Let the tires cool overnight or for a few hours after driving. This gives a more accurate read, since vehicle manufacturers specify PSI by assuming tires are 'cool.' (Recommended tire pressure takes into account the fact that tires heat up from driving, hence the reason the PSI number is for when the tires are cooler)
- Remove the valve cap from your tire.
- Press the tire pressure gauge into the valve firmly so that no escaping air is heard.
- Write down the tires' PSI levels as shown on the gauge and compare them to the manufacturer's recommended PSI. To find the PSI for your specific vehicle, look for a sticker on the driver's side door jam or the owner's manual (common tire pressures fall between 28 and 36 PSI). Note: Not all vehicles have the same tire pressure, and it's common for the PSI to be different in the front compared to the rear tires.
You can now either use a portable air compressor to refill too-low tires or go to a gas station where air compressor stations are common, and in many cases, free or really cheap to use. (The handy website FreeAirPump.com shows free air for tires near you).
Don't have a gauge? Take the vehicle to a mechanic, who can check the pressure for you.
Is it dangerous to drive with low tire pressure?
A total of 562 people died on the road in tire-related crashes in 2022, according to the latest report by the National Highway Traffic Safety Administration, part of the U.S. Department of Transportation.
Poor tire maintenance includes failure to rotate tires or insufficient air that could lead to flat tires, blowouts and crashes, according to an accident analysis published by the Association for the Advancement of Automotive Medicine.
"Regular monitoring and timely maintenance of the vehicle’s tires is required to ensure vehicle safety and economic fuel consumption," the study says. "But unfortunately, a substantial proportion of the population is not aware of tire aging as a potential hazard."
The study goes on to state that drivers tend to pay more attention to other parts of their vehicle, such as the engine and radiator, with just 19% of consumers studied that had their tires properly inflated.
Under law, all vehicles model year 2008 or newer are required to be equipped with the TPMS warning light.
If the light comes on, don't ignore it; you could suffer a flat tire, or worse, a tire blowout, said the AAA. According to Car and Driver print and digital magazine, the warning light turns on when pressure has dropped 25%, with some manufacturers programming the light to come on with a 10% pressure drop, which is long before it's even visible to the eye.
While in motion, an underinflated tire can blow out when the sides of the tire come into contact with the roadway. Since the sides are not intended to touch the road, they are thinner and weaker, causing these spots to give way, according to AAA.
While the serious safety hazards are of the greatest concern, low tire pressure can also cost you at the pump. If you follow every tip in the book to improve fuel economy in the winter but still have under-inflated tires, "you'll never reach optimal efficiency," said the AAA .
The next time that pesky light pops up in your car, or you notice a tire looks a bit low or the vehicle feels "off," put on a pair of gloves and pull out the tire gauge. It could save your life, or someone else's.
Email: lcomstock@njherald.com ; Twitter: @LoriComstockNJH or on Facebook .
This article originally appeared on New Jersey Herald: Seeing low tire-pressure warning light on your vehicle? Find out why and what to do
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