Cue those tire pressure lights!

October and November are big months for the infamous lights
Cold WX Tire Pressure
Cold WX Tire Pressure
Published: Oct. 18, 2021 at 11:24 AM CDT
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MONTGOMERY, Ala. (WSFA) - Did your tire pressure light come on this morning? If so, you certainly weren’t alone. Temperatures fell into the upper 30s and lower 40s in most locations for only the second time since spring.

It was actually the coldest morning in Montgomery in 179 days with an official low temperature of 42 degrees.

Temps that low will cause even the best, newest tires see their pressure levels drop a bit courtesy of the molecules within your tires huddling up and moving slower than normal. The bad news is a dashboard light coming on in your car usually always means some sort of attention is needed -- in this case it’s just more air.

With a starting pressure of 32 psi, here's what would happen based on the temperature.
With a starting pressure of 32 psi, here's what would happen based on the temperature.(WSFA 12 News)

But the good news is seeing your tire pressure drop this time of year is perfectly normal and expected.

But how is an alert light coming on normal?

Your tire pressure is still in “summer mode.” In other words, your the pressure in your tires is set to be “normal” for hot temperatures (80s and 90s) during the day and warm temperatures (60s and 70s) at night. Now that we’ve seen a morning in the 40s, your tires lost pressure because they aren’t in fall mode yet.

Tire pressure drops when it gets colder outside.
Tire pressure drops when it gets colder outside.(WSFA 12 News)

Tires typically lose about 1 psi for every temperature drop of 10 degrees. So when we go from the toasty temps we saw through the first half of October to the lower 40s this morning, your tires likely saw a drop of roughly 2-5 psi.

That drop won’t last, though.

That’s because after a cool to chilly start, we warm right back up into the 70s. That’s a 30-degree increase between between morning and afternoon. The result is a subsequent increase in your tire pressure by 2-4 psi from the time you leave your house in the morning to the time you leave work in the afternoon. It’s also important to note that by simply driving your vehicle for 5-10 minutes on a chilly morning, your tire pressure will increase 1-3 psi simply due to air molecules moving faster.

Therefore, it’s very possible that during the warmer afternoons, your tire pressure light will turn off without you actually adding any air. Still, you should strongly consider adding air to your tires as we round out October.

Most vehicles suggest keeping your tire pressure between 30 and 35 psi, with most in the 32-35 range. If you’re unsure of your vehicle’s suggested tire pressure, you can find it on a sticker inside the driver’s door, or by consulting your vehicle’s manual.

Tire pressure drops when it gets cold.
Tire pressure drops when it gets cold.(WSFA 12 News)

If you notice your pressure down in the upper 20s -- or if your tire pressure light comes on -- during these cool mornings, it’s a good idea to add some air because even the heating of the day won’t get you up to where you need to be in some instances. And it’s vital to have adequate amounts of air in your tires because low pressure can result in less-than-ideal driving conditions...

  • Poor fuel economy
  • Shorter lifespan of your tires
  • More time to come to a stop

Be careful about when you filly our tires, though! It’s suggested to fill your tires during the morning or after your vehicle has been sitting in a shaded area for 4-6 hours because the manufacturer’s suggested psi numbers assume “rested tires,” or tires that are “cold.”

Even with stretches of warmer weather -- the next 7-10 days, for example -- it’s imperative to fill your tires on a cooler morning to ensure your tires are good to go for future bouts with cooler weather.

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