Cold weather affecting PSI
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Hi Kids!
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From: NoVA (South Riding)
Yesterday the temp here in VA dipped to 25 degrees and when I started my car the low PSI warning went off. All four tires fell to 29 PSI and eventually rised to 32 PSI after reaching operating temp. Before the termperature dip the tires had a PSI of 36 at operating temp. Anyone else experince this?
One way that you can avoid the temperature effect on your tire pressure is to make the switch to Nitrogen. Because it is "dry", it doesn't suffer the wide range of expansion and contraction from a large temperature delta that regular, humid air does.
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Actually, the PV=nRT equation is the one that comes into play here. P = (nR/V)T tells you that pressure varies directly with temperature assuming that the volume (V) and number of molecules of the gas (n) are the same.
V/T=k make the assumption that pressure is constant which is obviously not the case as the OP observed.
V/T=k make the assumption that pressure is constant which is obviously not the case as the OP observed.
As Dave mentions, you can mitigate psi variations by filling with nitrogen. The benefit nitrogen provides is arguable, but I notice a difference. I’m in a much colder climate than you. Winter temperatures fluctuate greatly in Minnesota, going from freezing to -25 Fahrenheit.
I’ve also notice that it is easier to maintain psi within the correct range when running 17” wheels vs. lower profile tires on 18” wheels. Again, I’m in a very cold climate.
My tire guy makes another point about nitrogen. He says that nitrogen maintains a drier environment inside the tire that prevents condensation on the inside part of the wheel. I have no idea if that is true, but if so, that is certainly another reason to fill with nitrogen.
--Spike
I’ve also notice that it is easier to maintain psi within the correct range when running 17” wheels vs. lower profile tires on 18” wheels. Again, I’m in a very cold climate.
My tire guy makes another point about nitrogen. He says that nitrogen maintains a drier environment inside the tire that prevents condensation on the inside part of the wheel. I have no idea if that is true, but if so, that is certainly another reason to fill with nitrogen.
--Spike
Actually, the PV=nRT equation is the one that comes into play here. P = (nR/V)T tells you that pressure varies directly with temperature assuming that the volume (V) and number of molecules of the gas (n) are the same.
V/T=k make the assumption that pressure is constant which is obviously not the case as the OP observed.
V/T=k make the assumption that pressure is constant which is obviously not the case as the OP observed.
Thread Starter
Hi Kids!
iTrader: (8)
Joined: Dec 2007
Posts: 4,463
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From: NoVA (South Riding)
I started a thread in my350Z.com without doing a search. I will take full responsibility for the ensuing flaming 
I figured it was due to the low ambient temperature but since it didn't happen to me last winter, I decided to seek advice on the forum.
And to make the forum correctness ***** happy: what's the best C.A.I for the Z?

I figured it was due to the low ambient temperature but since it didn't happen to me last winter, I decided to seek advice on the forum.

And to make the forum correctness ***** happy: what's the best C.A.I for the Z?
Oh, that's easy. The one that lets the most air through without allowing it to heat up much while having a filter that doesn't clog easily or be in a position to allow the ingestion of water. It also helps if it looks good.
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