# Proper cold weather tire inflation practice? **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** impreza, air-pressure, tires, subaru\ **Created:** [January 16, 2017, 5:20pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610 "2017-01-16T17:20:43Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![lion9car](https://avatars.discourse-cdn.com/v4/letter/l/59ef9b/32.png) [@lion9car](https://community.cartalk.com/u/lion9car)\ **Post date:** [January 17, 2017, 6:54am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/21 "2017-01-17T06:54:03Z")
> [@pleasedodgevan2](#): > > One day in November the TPMS light came on so I put more air in the tires. I won’t check them unless the light comes on again. Given that the TPMS light generally comes on only when the tires are seriously underinflated, this is not a good approach to use. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [January 17, 2017, 7:13am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/22 "2017-01-17T07:13:26Z")
> [@lion9car](#): > > Given that the TPMS light generally comes on only when the tires are seriously underinflated Generally about 6 PSI low. not enough to cause any symptoms. Many people tire from seeking assistance when the warning light comes on, they begin to ignore it. Today I had a car come in with 20 PSI in the tires, the warning light must have been on for a year. ---
**Author:** ![BillRussell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/billrussell/32/3179_2.png) [@BillRussell](https://community.cartalk.com/u/BillRussell)\ **Post date:** [January 17, 2017, 12:37pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/23 "2017-01-17T12:37:30Z")
Actually, 1 PSI = 10ºF is an approximation. The actual formula is more complicated. Over a range in temps and pressures, that varies from 0.80 to 0.93 PSI/10ºF For example at 28 PSI and 60ºF initial, change is 0.82/10º PSI for change to 50ºF I have a spread sheet that does this calculation. First convert temps and pressure to absolute (I used kelvins and Pa). Then use P2 = P1(T2/T1) for new temp to get new pressure, and convert to relative PSI. But this does not take into account the small change in volume as pressure increases, ie the tire expands slightly as pressure increases. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [January 17, 2017, 2:12pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/24 "2017-01-17T14:12:44Z")
> [@bing](#): > > In cold weather I’d rather have a slightly over-inflated tire than one way under-inflated +1 That is also my approach. A slightly overinflated tire is not going to produce any problems unless one considers a somewhat harder ride to be significant. On the other hand, an underinflated tire can cause damage to the sidewall, and that is something that should be avoided if at all possible. The placard on my Outback’s door jamb specifies 32 psi front/30 psi rear. When the temps plummeted to less than 20 degrees a few weeks ago, I found that they were down to 30/28, so I used my compressor to bring them up to 34/32. When the temps rise, they will probably be something like 36/34, but that pressure is not problematic, and when the temps drop again, I won’t have underinflated tires. ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [January 17, 2017, 2:44pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/25 "2017-01-17T14:44:32Z")
Temps fluctuate so much this time of year here in NH. With a week it sent from -5 to 60. That’s a big enough swing to effect pressure. ---
**Author:** ![B.L.E](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@B.L.E](https://community.cartalk.com/u/B.L.E)\ **Post date:** [January 18, 2017, 1:00am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/26 "2017-01-18T01:00:12Z")
> [@BillRussell](#): > > I have a spread sheet that does this calculation.First convert temps and pressure to absolute (I used kelvins and Pa). Then use P2 = P1(T2/T1) for new temp to get new pressure, and convert to relative PSI. I find it simpler to just convert Fahrenheit to Rankine. Simply add 459.67 to the Fahrenheit temperature and you have Rankine. No need to do a two step conversion first from F to C, and then C to K. Also, I convert psi gauge to psi absolute by adding 14.7 to the gauge reading. Naturally, if you live on top of Pike’s Peak, that 14.7 number will be wrong. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [January 18, 2017, 2:34am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/27 "2017-01-18T02:34:59Z")
Is it possible an average daily driver like me that gets air pressure checked at every oil change is negligent? Sorry you guys are anal retentive, but only 40 years under my belt and driving on without obsessing about temp and tire pressure. ---
**Author:** ![B.L.E](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@B.L.E](https://community.cartalk.com/u/B.L.E)\ **Post date:** [January 18, 2017, 3:04am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/28 "2017-01-18T03:04:04Z")
I’ll have to say one thing, at -40, you won’t have to worry about your tires overheating due to only being inflated to 23 psi. Driving at highway speeds should warm them up to at least zero. If Tom Brady’s football was inflated to a legal 12.5 psi in a 60 degree room, but the temps on the playing field was -40, the pressure would drop to an illegal 7.27 psi. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [January 18, 2017, 3:11am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/29 "2017-01-18T03:11:24Z")
I’ve been in Minnesota and South Dakota most of my life and I can’t say that I ever saw 40 below zero. 27 maybe but that’s about it. When it starts to get cold outside I just watch the tire pressure and when it gets a few pounds low due to temps, I add some air. That’s about it for me. ---
**Author:** ![pleasedodgevan2](https://avatars.discourse-cdn.com/v4/letter/p/ad7895/32.png) [@pleasedodgevan2](https://community.cartalk.com/u/pleasedodgevan2)\ **Post date:** [January 18, 2017, 5:51am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/30 "2017-01-18T05:51:39Z")
I saw -40 once or twice. I was leaving the dorm in Limestone Me. one cold morning when I realized that I couldn’t breathe. I immediately put my hands over my mouth and exhaled and then was able to breathe slightly warmer air for a few breaths until I was used to the dry, cold air. 115 degree difference can be hard to take. ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [January 18, 2017, 1:55pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/31 "2017-01-18T13:55:44Z")
I’ve seen -30 and below a few times at 4am in the White Mountains. We usually get up that early on Sunday to head back south from skiing before the traffic picks up. It’s COLD. -40 isn’t unheard of either. ---
**Author:** ![ibrewster](https://avatars.discourse-cdn.com/v4/letter/i/838e76/32.png) [@ibrewster](https://community.cartalk.com/u/ibrewster)\ **Post date:** [January 18, 2017, 5:02pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/32 "2017-01-18T17:02:42Z")
As I write this, the thermometer outside my office window reads -43ºF. The _official_ temperature, at the airport here (which is actually only about half a mile away), reads -47ºF (feels like -60, according to [www.wunderground.com](http://www.wunderground.com)). And it’s only supposed to get colder today. Tomorrow it’s supposed to warm up though: the high is -42ºF, or maybe -36ºF, depending on where you look 😃 Add to that a lovely ice fog that severely limits visibility, and you get the reason I posted this thread - I do _not_ want to be dealing with a flat - or even just low tire pressure - in these conditions 🙂 ---
**Author:** ![eddo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/eddo/32/2594_2.png) [@eddo](https://community.cartalk.com/u/eddo)\ **Post date:** [January 18, 2017, 6:38pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/33 "2017-01-18T18:38:42Z")
I’m not usually much of an advocate for Nitrogen in tires, but this seems like a perfect scenario for one. Wouldn’t it? A 100 degree shift in cold temp on the tires is not something I have any experience with (I’d move or set my self on fire to stay warm if it ever got near 0 degrees where I was, much less below zero…) but nitrogen int he tires is there for this very reason- to keep tire pressures consistent. that, and those snazzy green valvecaps. 🙂 ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [January 18, 2017, 6:46pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/34 "2017-01-18T18:46:59Z")
[http://www.getnitrogen.org/sub.php?view=getTheFacts&subpage=temperatureeffects](http://www.getnitrogen.org/sub.php?view=getTheFacts&subpage=temperatureeffects) ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [January 18, 2017, 6:51pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/35 "2017-01-18T18:51:16Z")
Nitrogen is subject to the same laws for gases that air is. It does not maintain a constant pressure for changes in temperature. BTW air is 78% nitrogen and when pure nitrogen is put in a tire, there is already one ATM of air in there. To have 100% nitrogen in a tire, the tire would have to be filled in a vacuum chamber. At best, you will get about 91% nitrogen. The only advantage to a nitrogen fill is that the nitrogen usually is dry, but there will still be some moisture in the tire from the air that is in there at the start. ---
**Author:** ![BillRussell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/billrussell/32/3179_2.png) [@BillRussell](https://community.cartalk.com/u/BillRussell)\ **Post date:** [January 18, 2017, 7:28pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/36 "2017-01-18T19:28:10Z")
Keith is entirely correct. Use of Nitrogen has zero advantages. ---
**Author:** ![B.L.E](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@B.L.E](https://community.cartalk.com/u/B.L.E)\ **Post date:** [January 19, 2017, 12:50am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/37 "2017-01-19T00:50:46Z")
> [@ibrewster](#): > > The official temperature, at the airport here (which is actually only about half a mile away), reads -47ºF At that temperature, you could saw open your propane cylinder and pour the liquid propane out into a bucket. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [January 19, 2017, 7:27am UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/38 "2017-01-19T07:27:13Z")
Gotta be Alaska, Northern Canada, or Siberia. No place in the lower 48 have those kinds of temps that I can see. My sympathy. ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [January 19, 2017, 2:18pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/39 "2017-01-19T14:18:41Z")
> [@bing](#): > > No place in the lower 48 have those kinds of temps that I can see. Not many times…but it does happen… > **[The coldest temperatures ever recorded in New York State](https://cnycentral.com/news/local/the-coldest-temperatures-ever-recorded-in-new-york-state)** > > The coldest temperature ever recorded in New York State was in Old Forge. -30 in the White Mountain ski area is not unheard of. I’ve seen it more then once. ---
**Author:** ![ibrewster](https://avatars.discourse-cdn.com/v4/letter/i/838e76/32.png) [@ibrewster](https://community.cartalk.com/u/ibrewster)\ **Post date:** [January 19, 2017, 2:36pm UTC](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610/40 "2017-01-19T14:36:07Z")
> [@bing](#): > > Gotta be Alaska, Northern Canada, or Siberia. No place in the lower 48 have those kinds of temps that I can see. My sympathy. Yep, Alaska. Fairbanks, to be specific. Warmed up to -34ºF this morning though, so not so bad 🙂 [Previous page](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610.md?page=1) [Next page](https://community.cartalk.com/t/proper-cold-weather-tire-inflation-practice/98610.md?page=3)