Cold Tire Pressure

"zeontestpilot" (zeontestpilot) 02/18/2016 at 08:20 • Filed to: None

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So the cold tire pressure is suppose to be at 30 psi for my car. Well it’s 5F out today and one of the tires went down to 24 psi. Naturally that exciting “low tire pressure” light came on. I’m gonna inflate it a bit later today, but should I put it to 30 psi, or maybe a high 20? I know once the temp goes up, the air expands and improves the psi, so I’m unsure what to fill it up to.

Smallbear wants a modern Syclone, local Maple Leafs spammer > zeontestpilot 02/18/2016 at 08:25

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Leave it alone and let it go back to where it’s supposed to be?

Or if it’s just one tire, measure the others and match them, since they must have had a little more air to start with.

McMike > zeontestpilot 02/18/2016 at 08:29

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one of the tires went down to 24 psi.

What were the other tires at?

zeontestpilot > Smallbear wants a modern Syclone, local Maple Leafs spammer 02/18/2016 at 08:29

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I was going to match them, because they became uneven for some reason...

zeontestpilot > McMike 02/18/2016 at 08:31

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Umm...let me think..

LF: 28 RF: 24

LR: 30 (?) RR: 27 (?)

I have to even it out later today, make it even at least.

Patrick Nichols > zeontestpilot 02/18/2016 at 08:32

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You can always over inflate a bit. My factory setting is 33 but I put it to 35 most of the time for the empeegees

Party-vi > zeontestpilot 02/18/2016 at 08:36

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Inflate to 30psi. The manufacturer took the expansion of air as the tires heat up into account when they determined the tire air pressures for your vehicle. Make sure all your tires are at 30psi.

Smallbear wants a modern Syclone, local Maple Leafs spammer > Party-vi 02/18/2016 at 08:46

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At 5 degrees, when that warms up it’s going to be well over spec. It’s OK for now, as long as he checks and deflates them once it’s warmed up to whatever the average temp is at this time of year for the area.

You can tell a Finn but you can't tell him much > zeontestpilot 02/18/2016 at 08:47

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A rule of thumb is that a tire loses 1 psi for every 10 degree F temperature drop and 1 psi per month. I would inflate the tires to recommended 30 psi all around.

zeontestpilot > Smallbear wants a modern Syclone, local Maple Leafs spammer 02/18/2016 at 08:54

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It’s Michigan, so the average temp is at the whim of Mother Nature. :)

zeontestpilot > You can tell a Finn but you can't tell him much 02/18/2016 at 08:55

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Good rule of thumb, thanks

Peptide > Party-vi 02/18/2016 at 09:00

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Agreed; tire pressure recommendations are based on maintaining load capacity, preventing excessive sidewall flex and keeping the tire temperature in the correct operating region. The cold-tire pressure recommendations are not adjusted for temperature and need to be checked when the ambient temperature changes:

https://corporate.goodyear.com/en-US/media/ne…

“Odds are that many motorists haven’t checked their tire pressure since the weather began turning cooler. If the last time the tire pressure was checked was during the heat of summer, with temperatures around 80 or 90 degrees, many people could soon be riding on severely underinflated tires without realizing it,” said Gary Medalis, Goodyear brand general manager.

McMike > zeontestpilot 02/18/2016 at 09:00

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Inflate the RF to 28, or take them all up to 30.

jariten1781 > zeontestpilot 02/18/2016 at 09:03

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I adjust if there’s a swing >~10% (so around 3-4 psi). If that means I have to air up for a few days for a cold snap then let it out a few days later due to a heat wave...so be it.

Remember to check pressure on cold, not recently driven tires and keep it at the manufacturers spec unless you have a specific reason to be aired up or down.

Party-vi > Smallbear wants a modern Syclone, local Maple Leafs spammer 02/18/2016 at 09:03

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You’re assuming the tires will warm to the same temperature in 5 degree weather that they will in 70 degree weather after operation. I still say to follow what the big white and yellow sticker says.

Smallbear wants a modern Syclone, local Maple Leafs spammer > Party-vi 02/18/2016 at 09:12

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No, I meant as the ambient temp rises. As long as that doesn’t come up drastically (it’s been fluctuating wildly here—often 15-20 degrees Celsius within 24 hours—and I’m in roughly the same bit of territory as ztp) by all means go by the big white and yellow sticker. If it does jump a large amount, and the temperatures are due to spike well above freezing (so around a 40 Fahrenheit jump) this weekend, then he needs to check them again then. Personally I’d even them out now so it’s not dangerously low and let the pressure come up on it’s own.

Party-vi > Smallbear wants a modern Syclone, local Maple Leafs spammer 02/18/2016 at 09:13

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Ah got it.

zeontestpilot > jariten1781 02/18/2016 at 09:15

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Yep, when I got to work the psi was 28. I knew driving it would take that annoying alert away. Just have to inflate now.

LOREM IPSUM > zeontestpilot 02/18/2016 at 10:16

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Also worth mentioning is that the sticker only really applies to the factory equipped wheel and tire combination. If you’re running aftermarket equipment such as upsized wheels and tires, the data on the sticker might not be best for your particular situation.

Infared temp guns can come in handy here. Set your baseline air pressure. Go for a drive to warm up the tires. After a couple of hot laps quickly get out and use the ir gun to measure the temperature across the tires tread.

Hotter in center: lower psi.

Hotter at edge of tire where tread meets sidewall: Raise psi.

Then go for a few more hot laps and quickly recheck tread temps. Keep at it until you have a consistent temp...

...then move on to the next wheel.