# Low Tire Pressure - leak or extreme cold? **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [February 26, 2015, 5:22am UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153 "2015-02-26T05:22:55Z")\ **Posts on this page:** 12\ **Page:** 3
**Author:** ![CapriRacer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/capriracer/32/22_2.png) [@CapriRacer](https://community.cartalk.com/u/CapriRacer)\ **Post date:** [February 28, 2015, 5:32pm UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/41 "2015-02-28T17:32:21Z")
I had to go back to figure out why this thread became a talking point about global warming. ---
**Author:** ![idiot666](https://avatars.discourse-cdn.com/v4/letter/i/c68b51/32.png) [@idiot666](https://community.cartalk.com/u/idiot666)\ **Post date:** [February 28, 2015, 6:20pm UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/42 "2015-02-28T18:20:11Z")
Low tires decrease mpg. 😃 ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [March 5, 2015, 9:24am UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/43 "2015-03-05T09:24:18Z")
Ice can sometimes get form in the valve stem area in freezing temps and cause a tire leak. Dry all the valve stems out and put new caps on and keep them tight. Might help. ---
**Author:** ![CapriRacer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/capriracer/32/22_2.png) [@CapriRacer](https://community.cartalk.com/u/CapriRacer)\ **Post date:** [March 5, 2015, 5:51pm UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/44 "2015-03-05T17:51:57Z")
GeorgeSanJose said: “Ice can sometimes get form in the valve stem area in freezing temps and cause a tire leak…” Ice can sometimes form in 37°F temps, so I recommend NOT checking tire pressure when it is below 40°F ---
**Author:** ![meanjoe75fan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/meanjoe75fan/32/552_2.png) [@meanjoe75fan](https://community.cartalk.com/u/meanjoe75fan)\ **Post date:** [March 5, 2015, 8:04pm UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/45 "2015-03-05T20:04:23Z")
^Go all winter without checking pressure? I recognize your expertise, but that seems…extreme. ---
**Author:** ![idiot666](https://avatars.discourse-cdn.com/v4/letter/i/c68b51/32.png) [@idiot666](https://community.cartalk.com/u/idiot666)\ **Post date:** [March 5, 2015, 10:46pm UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/46 "2015-03-05T22:46:37Z")
I’m interested in this ice that forms at 37F. You could win a Nobel Prize for this discovery. ---
**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:** [March 6, 2015, 1:08am UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/47 "2015-03-06T01:08:40Z")
The air coming out of the compressor can be much colder than the ambient temp. In cold weather I agree you need to be careful with moisture. I always let a little more air out of the tire before adding air just to make sure frost is cleared out of the valve. But then I have a warm garage too and would never use an outside air source in the winter unless I had to. ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [March 6, 2015, 1:44am UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/48 "2015-03-06T01:44:11Z")
> "The air coming out of the compressor can be much colder than the ambient temp." It would only be about 3 deg F colder from a 140 psig compressor. ---
**Author:** ![meanjoe75fan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/meanjoe75fan/32/552_2.png) [@meanjoe75fan](https://community.cartalk.com/u/meanjoe75fan)\ **Post date:** [March 6, 2015, 3:19am UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/49 "2015-03-06T03:19:29Z")
@idiot, Ever heard of adiabadic compression? Pressures go up/down; so does temperatures. Actually, I’m surprised letting 36 PSI out of a tire only results in a 5F drop! ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [March 6, 2015, 7:01am UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/50 "2015-03-06T07:01:29Z")
> "Ever heard of adiaba[t]ic compression?" Actually, since the air does no net work coming out the valve, adiabatic expansion doesn’t play a role. Only the Joule-Thomson expansion coefficient applies. If air were ideal, there would be no cooling, but since it has a positive coefficient of about 0.25 K/bar, you see the minor cooling I mentioned above. Helium or hydrogen would warm slightly coming out the valve because they have negative J-T coefficients. ---
**Author:** ![CapriRacer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/capriracer/32/22_2.png) [@CapriRacer](https://community.cartalk.com/u/CapriRacer)\ **Post date:** [March 6, 2015, 5:54pm UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/51 "2015-03-06T17:54:58Z")
meanjoe75fan said: “…^Go all winter without checking pressure?..” I didn’t say that. Surely there are times where your car in parked where the temp is above 40F sometime in the winter. Idiot666 said: “…I’m interested in this ice that forms at 37F. You could win a Nobel Prize for this discovery…” [atmos.washington.edu/cliff/Roadway2.htm](http://www.atmos.washington.edu/cliff/Roadway2.htm) Extracted from that: “…Thus, frost can be occurring at the surface even when official temperature observations are reporting temperatures of 35 to 37F…” And as been been mentioned above, air escaping from a high pressure to a lower pressure cools and can form ice. ---
**Author:** ![idiot666](https://avatars.discourse-cdn.com/v4/letter/i/c68b51/32.png) [@idiot666](https://community.cartalk.com/u/idiot666)\ **Post date:** [March 7, 2015, 8:59am UTC](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153/52 "2015-03-07T08:59:23Z")
Actually both disprove your point. Joule Throttling lowers the temperature. Official temperature stations are set like 6 feet high so it is not measuring the road surface temperature. Plus the weather station can be many miles away. In either case, the water is not freezing at 37F. [Previous page](https://community.cartalk.com/t/low-tire-pressure-leak-or-extreme-cold/89153.md?page=2)