Stonehenge, the Lost City of Atlantis, Cleopatra’s tomb, and the question of “what the heck just happened to my tire pressure!?” all belong in pretty much the same category of mysteries. Maybe you’ve sat there staring and pondering your tire pressure warning light much the same as archaeologists contemplate Stonehenge.
Thing is though, Stonehenge isn’t going anywhere, but you need to. You require answers to your tire pressure mystery now, Stonehenge can wait.
Alright, alright…we got you. Here’s the deal.
If you suddenly find yourself low on tire pressure, especially on all four tires, an outside temperature drop is a very likely cause.
Across large sections of the United States, the significant seasonal temperature fluctuations can really wreak havoc on tire pressure.
If a recent vehicle service check involved tire pressure verification and adjustment, drivers can be particularly confused by a surprise tire pressure warning light. The old “but I just had the car serviced last week!” sentiment.
We feel you, but very inconveniently Mother Nature doesn’t care. Gas expands when heated and contracts when temperatures drop. If your tire pressure is dialed in at 50° F, for example, then a drop of 30° or 40° into sub-freezing territory means you could be meaningfully below vehicle psi specification, and that can trigger the Tire Pressure Monitoring System (TPMS) warning light.
If optimal tire grip and performance, as well as maximum tire life are the goals, then tire pressure has to be adjusted according to the temperatures of the moment, so to speak. In times of severely fluctuating temperatures, tire pressure should be monitored and adjusted with greater regularity. If you’re experiencing a particularly frigid spell, and your tires have dropped into the low pressure “warning” zone, then inflation back to specification is the only solution.
Here’re more on knowing your tire pressure and how to check tire pressure.
You might be thinking: a drop in tire pressure due to falling temperatures seems innocent enough. Can’t I just wait it out?
We really don’t recommend that you do. It’s not just because we’re tire people. Tire pressure has a real, direct influence on vehicle safety and performance. If tires are low enough to trigger a TPMS warning light, then that opens the door to handling and traction consequences – a loss of high speed maneuverability and braking performance, less traction in wet conditions due to a sub-optimal contact patch, and more. If you’re towing or carrying a heavy vehicle load, the risks are multiplied with low tire pressure.
Bottom line: Your vehicle was engineered and tested to operate within a specific tire psi window. To maintain its performance and safety attributes, tire pressure has to be addressed. Like changing the oil, tire pressure is just one of those inconvenient automotive deals.
A good estimate is for every 10° fluctuation in air temperature, vehicle tire pressure will adjust by about 1 psi. So if outside air temperature decreases 30° from your last tire pressure adjustment, expect tire pressure to drop about 3 psi.
If temperatures get particularly arctic, the rate at which tires deflate can be greater than the 1 psi per 10° rule of thumb. The low psi warning light pictured above was triggered on a -11° morning after a ~55° drop in temperature from the last tire psi adjustment. The tires pressure fell 8 psi overall due to that temperature drop. (Yes, if you’re keeping score at home, we noted the air temperature when that vehicle’s tires were last adjusted to specification.)
If tire pressure is determined in sub-freezing conditions and air temperature drastically increases, then you’ll be faced with potential tire over-inflation. Once again, for every 10° fluctuation in temperature (up or down), tires will adjust by about 1 psi. The thing is, unlike when tires drop notably below vehicle specification, your TPMS warning system will not alert you to over-inflation.
Like under-inflation, tire over-inflation can affect performance and traction. Over-inflation is also a very common cause of premature tire wear because it so often goes unnoticed.
Our advice is to make tire pressure monitoring a periodic automotive maintenance item, like oil changes. This doesn’t mean you have to obsess about tire pressure and adjust on a daily basis, but if all of a sudden you’re either grabbing your down winter jacket and gloves, or a bathing suit and sunscreen on the way out the door, it’s probably time to think about a tire pressure adjustment to match the season.
Hey, at least it’s easier than solving Stonehenge.
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