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Cold weather caused low temperature tire warning.

Rachmaninov

Supporting Member
Supporting Member
Jul 17, 2019
220
146
NJ
I’m getting a low temperature warning on all 4 of my 19 Continental (OEM) tires this morning.

The warning says they’re all at 36 first thing this morning.

The temperature here did drop to 28* this morning but I’m surprised that the tires would all lose pressure because of the cold.

Is this a normal situation?

Should I set them all to 42* cold.
Thanks
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Supporting Member
Mar 8, 2012
19,946
23,830
Texas
It's totally normal and happens to every car. Cold weather, add air. And the kind of gas you add doesn't make a whit of difference. Nitrogen shrinks with cold weather too, however, it's a nice scam for the uninformed.
 

KG2V

Member
Mar 9, 2019
203
158
Bayside, NY
Unless you use nitrogen as the “air”, you will see this on any vehicle.
You'll see it with nitrogen too - it also follows Boyle's law. If you use DRY air, and DRY nitrogen, they react identically to air temperature change. That said, nitrogen is more likely to be dry, vs the air from a compressor unless they put a dryer inline
 

KG2V

Member
Mar 9, 2019
203
158
Bayside, NY
PV=nRT is actually the ideal gas law, but the end result still stands. Temperature drops, so does pressure. Just happened to my wife's car yesterday.
Yeah, but at "Normal" temperatures (no signnificant diferences above 200K.) and presures below about 200bar (nearly 3000 PSI), we can pretty much ignore that air isn't an ideal gas
The only significant difference is water vapor pressure. Most of those little vibrating compressors, and even big ones without either an intercooler or a air dryer deliver air that is close to saturation (aka 100% RH), where a tank if nitrogen is typically 0% RH (as they are usually filled off a source of liquid nitrogen)
(Spent 10 years of my life playing with LN2 and stuff in nitrogen atmospherss, mostly only to 100 PSI)
 
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KG2V

Member
Mar 9, 2019
203
158
Bayside, NY
And yes, there is at least some other thoretical reasons to use Nitrogen (but not temp/pressure), however with air being 78% nitrogen to begin with, the effects are a lot less than you think. The big one would be slow oxydation of runner/rims etc. The pressure swings (like I said) have more to do with water vapor (no matter what popular mechanics says RE temperature/pressure. The issue is also NOT "Migration through the rubber" (there is a 2.6% difference in size) - any issue is actually the inner surface of the tire actually oxydizing.
Most of the benefits which are there in theory aren't really there, in practice. As I said, the BIG one is the N2 being DRY vs air typically being about 1% water vapor, which seriously affects the n in PV=nRT, so you get a fall in both n and T (multiplicitive) which will change P. That is why I'm always careful to say DRY air (my compressors usually have a dessicant air dryer on them, because paint doesn't like water - I airbrush models, so water is an issue)
I mean' if you want big molecules, you could fill your tires with Carbon Dioxide. MUCH bigger than O2 or N2, cheap, and ALMOST non reactive. If you wanted to go nuts, you could use Argon. Totally non reactive, larger than N2 (yes, more expensive, but still commonly available - any welding supply house)
 
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jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Supporting Member
Mar 8, 2012
19,946
23,830
Texas
And yes, there is at least some other thoretical reasons to use Nitrogen (but not temp/pressure), however with air being 78% nitrogen to begin with, the effects are a lot less than you think. The big one would be slow oxydation of runner/rims etc. The pressure swings (like I said) have more to do with water vapor (no matter what popular mechanics says RE temperature/pressure. The issue is also NOT "Migration through the rubber" (there is a 2.6% difference in size) - any issue is actually the inner surface of the tire actually oxydizing.
Most of the benefits which are there in theory aren't really there, in practice. As I said, the BIG one is the N2 being DRY vs air typically being about 1% water vapor, which seriously affects the n in PV=nRT, so you get a fall in both n and T (multiplicitive) which will change P. That is why I'm always careful to say DRY air (my compressors usually have a dessicant air dryer on them, because paint doesn't like water - I airbrush models, so water is an issue)
I mean' if you want big molecules, you could fill your tires with Carbon Dioxide. MUCH bigger than O2 or N2, cheap, and ALMOST non reactive. If you wanted to go nuts, you could use Argon. Totally non reactive, larger than N2 (yes, more expensive, but still commonly available - any welding supply house)
Correct. However, the dry nitrogen can be a detriment to normal on-road cars driven on the highway. The reason is that if the is a reasonable amount of water vapour in the air, the tire will reduce flexing faster (e.g. reach thermal equilibrium faster because water vapour expands faster than dry gas) and so run cooler and last longer.
Nitrogen is great for top race cars when tuning the suspension to get that last 1/100th second reduction in lap time because it is dry and so the laps are predictable. It's also great for underground mine vehicles and airplanes because if a fire breaks out, no additional oxygen is added. (Fire isn't an issue with above ground vehicles because there's plenty of oxygen in the air).
 
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ewoodrick

Well-Known Member
Apr 13, 2018
5,285
3,735
Buford, GA
I’m getting a low temperature warning on all 4 of my 19 Continental (OEM) tires this morning.

The warning says they’re all at 36 first thing this morning.

The temperature here did drop to 28* this morning but I’m surprised that the tires would all lose pressure because of the cold.

Is this a normal situation?

Should I set them all to 42* cold.
Thanks
Normal, happens to all tires.
 

Rachmaninov

Supporting Member
Supporting Member
Jul 17, 2019
220
146
NJ
FYI -
I did expect to add air due to cold weather but I was surprised at the drastic difference due to the recent temperature drop. I thought I was at 42 and it apparently dropped to 36 overnight. Just seemed to be a large drop but obviously not a big deal.

Thanks for the confirmation that it’s normal.
 

notinuse

Member
Mar 5, 2019
8
9
Wisconsin
Yeah, but at "Normal" temperatures (no signnificant diferences above 200K.) and presures below about 200bar (nearly 3000 PSI), we can pretty much ignore that air isn't an ideal gas
The only significant difference is water vapor pressure. Most of those little vibrating compressors, and even big ones without either an intercooler or a air dryer deliver air that is close to saturation (aka 100% RH), where a tank if nitrogen is typically 0% RH (as they are usually filled off a source of liquid nitrogen)
(Spent 10 years of my life playing with LN2 and stuff in nitrogen atmospherss, mostly only to 100 PSI)

Well, I just meant the equation wasn't Boyle's Law. I should have used its other name, the general gas equation.
 
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