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Cold weather caused low temperature tire warning.

Discussion in 'Model 3: Driving Dynamics' started by Rachmaninov, Nov 4, 2019.

  1. Rachmaninov

    Rachmaninov Supporting Member

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    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
     
  2. Rachmaninov

    Rachmaninov Supporting Member

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    42 lbs not 42*
     
  3. MNScott

    MNScott Member

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    Yes, you should set them to 42psi cold. This is a known issue with all inflated tires on all cars in cold weather.
     
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  4. VT_EE

    VT_EE Active Member

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    Unless you use nitrogen as the “air”, you will see this on any vehicle.
     
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  5. KG2V

    KG2V Member

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    Yes.
    Back to HS Physics: Boyle's Gas Law is PV=nRT. R is a constant, and in the case of a car tire, short term, V (volume) and n (number of gas mols in the tire) are effectively constant - that leaves P and T - to T goes down, P goes down
     
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  6. SSedan

    SSedan Active Member

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    See the post between ours.
     
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  7. jerry33

    jerry33 (S85-3/2/13 traded in) X LR: F2611##-3/27/20

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    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.
     
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  8. KG2V

    KG2V Member

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    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
     
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  9. notinuse

    notinuse Member

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    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.
     
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  10. WarpedOne

    WarpedOne Supreme Premier

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    I'm using 80% mixture of nitrogen and other gasses.
    The best compromise...
     
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  11. KG2V

    KG2V Member

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    I'm thinking you mean 78% with about 21% oxygen, and the rest "other"? ;)
     
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  12. VT_EE

    VT_EE Active Member

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  13. KG2V

    KG2V Member

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    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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  14. WarpedOne

    WarpedOne Supreme Premier

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    I allow for some 'bean emissions' in the vicinity of air compressor therefore I do not want to be too precise...
     
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  15. KG2V

    KG2V Member

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    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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  16. ewoodrick

    ewoodrick Well-Known Member

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    And you'll see this on enhanced nitrogen fills as well.
     
  17. jerry33

    jerry33 (S85-3/2/13 traded in) X LR: F2611##-3/27/20

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    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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  18. ewoodrick

    ewoodrick Well-Known Member

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    Normal, happens to all tires.
     
  19. Rachmaninov

    Rachmaninov Supporting Member

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    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.
     
  20. notinuse

    notinuse Member

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    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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