Yep - same with aircraft hydraulic accumulators. Nitrogen charged, and pressure varies with temperature...you have to compensate for temperature when doing the pre-flight inspection to know if it's at the acceptable pressure or not.
Nitrogen pressure fluctuation due to tempurature?
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Back of the napkin fun: The pressure for an ideal gas (N2 is close enough) at 85F (303K) should be about 8% higher than at 45F (280K). This assumes (wrongly, but by how much I have no idea) that the tires don't expand any as the pressure increases. 35PSI at 45F will climb to 38PSI at 85F; the reverse is the same.
Originally Posted By: calvin1
Back of the napkin fun: The pressure for an ideal gas (N2 is close enough) at 85F (303K) should be about 8% higher than at 45F (280K). This assumes (wrongly, but by how much I have no idea) that the tires don't expand any as the pressure increases. 35PSI at 45F will climb to 38PSI at 85F; the reverse is the same.
And, in light of that, I will adjust my monthly cold inflation pressure check (and fill) by 1 PSI/10 degrees F if the weather is unusual on that day. E.G. if it's normally 70, but that day it's 50...I will adjust to 1-2 PSI below normal...conversely, if it's 70 that day, and normally 50, or about to cool off, I will go 2 PSI over the normal cold pressure setting...so that my cold pressure setting is correct for the normal anticipated temperature range...
Just a bit OC...similar to most BITOGers and their oil selection...
Back of the napkin fun: The pressure for an ideal gas (N2 is close enough) at 85F (303K) should be about 8% higher than at 45F (280K). This assumes (wrongly, but by how much I have no idea) that the tires don't expand any as the pressure increases. 35PSI at 45F will climb to 38PSI at 85F; the reverse is the same.
And, in light of that, I will adjust my monthly cold inflation pressure check (and fill) by 1 PSI/10 degrees F if the weather is unusual on that day. E.G. if it's normally 70, but that day it's 50...I will adjust to 1-2 PSI below normal...conversely, if it's 70 that day, and normally 50, or about to cool off, I will go 2 PSI over the normal cold pressure setting...so that my cold pressure setting is correct for the normal anticipated temperature range...
Just a bit OC...similar to most BITOGers and their oil selection...
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