# Cold and tire pressure warning

I know that cold reduces pressure, but should it be enough to make my warning sensor go on?
No tire is visibly underinflated. Too cold to be messing with a tire gauge.

It can. The TPMS does not care what the temperature is.

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Yes, it could be cold enough to set off the warning. If itâ€™s too cold for you, you might go by a tire shop and have them inflate them to the recommended pressure.

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Yeah, that could kill youâ€¦

;-]

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Go out check one, go back in have hot chocolate , repeat until all tires checked.

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Easilyâ€¦especially if the tire pressure was a little low before the cold hit.

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According to the ideal gas law (which is pretty close for air at atmospheric temperatures and pressures), pressure is a direct function of temperature (P Ă— V = n Ă— R Ă— T). 0Â°F is 460Â° above absolute 0, so the difference between 0Â°F and 46Â°F would be 10%. -20Â°F and 72Â°F 20%.

Yes. Itâ€™s normally about 30 here overnight. Last week it got down to 3 overnight. My daughterâ€™s car tripped the TPS monitor. I checked it when the temperature was about 15 and about 15 minutes after she arrived. The lowest one was 27 psi. I think that is low enough to trip the TPS.

When using that formula, donâ€™t forget that the â€śPâ€ť in that formula refers to absolute pressure, not gauge pressure. If you are at sea level add 14.7 psi to the tireâ€™s gauge pressure, do the calculation, and then subtract 14.7 psi from the answer to get back to gauge pressure.
Both pressure and temperature must be measured on an absolute scale in that formula.

Isnâ€™t safety more important than minor temporary discomfort?

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Yup!
This morning, out of an abundance of caution, I gloved-up and went into the garage to check my tire pressure as a result of the consistently low temps for the last few weeks. The vehicle mfr specifies 32 psi in the front, and 30 psi in the rear, and I measured 33/31 on my Accu-gage, so I felt that no further action on my part was necessary. However, I began with tire pressure of 35 front/33 rear a few weeks ago, in anticipation of a precipitous drop in temperatures.

So, to answer the OPâ€™s questionâ€¦Yes, the recent low temperatures can certainly trigger your TPMS warning lightâ€¦if you didnâ€™t take care to inflate the tires to a few psi over the mfrâ€™s specification prior to the drop in temperatures. If you didnâ€™t take appropriate action earlier, then you really donâ€™t have much choice but to brave the cold, and inflate the tires properly now that the temp has dropped.

Have you tried changing a flat when itâ€™s extremely cold out?

A few winters ago went to White mountains for a ski trip. Sunday morning got in my 4runner to leave and the low pressure light was on. I got out my gauge and checked all the tiresâ€¦it was -15 with a wind chill of -40. But I wasnâ€™t going to chance getting a blowout 90 miles from home in that weather.

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Done it in the cold (maybe 10F) and snow, at night. Very glad I had practiced under better conditions in my garage.

I had to use the free air machine at the convenience store for all four tires because the crummy temperature drop. I did two tires on one side, got in truck pulled out of the way and used heated seat feature for a few minutes then did the other side.

Not to a lot of people I see on the road.

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can someone do the math? 32psi at 75F will result in what psi at 10f?

Whoops! Youâ€™re right. I made a spreadsheet. For a tire inflated to 30 psi changes in temperature are about 50% greater: a tire inflated to 30 psi @ 0Â°F would be 34.5 psi @ 46Â°F, 38.9 @ 92Â°F

â€ścan someone do the math? 32psi at 75F will result in what psi at 10f?â€ť

I get 26.3 psig.

I get the same.

Hereâ€™s the math: calculate a constant using the temperature and pressure at time of inflation by adding 460 to the temperature and 14.7 to the pressure, divide that pressure by that temperature:

(P0 + 14.7)/(T0 + 460)

for P0 = 32 , T0 = 75 , thatâ€™s .0873.

Use that constant to calculate for any T, remembering to add 460 to T then subtract 14.7 from the resultant P. A spreadsheet makes it easy.

Cold can and does make TPMS warning lights come on. Here is everything you need to know.. It is pretty well established that as the temp drops by 10 degrees F, tire pressure drops by about 1 psi. So, I agree with texases. If you own a vehicle with a pressure display it is easy to confirm any week you see a big temp drop (or increase).