presssure

[mcapocci]

In my prior post I discussed the change of pressure with altitude and temp. For us in the real world you need to know what kind of pressure gage you are using. I use a burden tube type. They are cheap round head Gage's and accurate. The pencil types are junk. A burdon tube measure relative pressure. Ie the difference between the outside atmosphere and the feed pressure. Spring gauges do not really do this ..they are set for sea level and wrong every where else. Tires are inflated structures. They operate not on absolute pressure but differential pressure ( within reason. Ie under a few tens of Ksi). So the use of a burdon gage requires no correction for altitude. Also do not correct for temperature. 25 psi differential is all you need to know if the tire is to be inflated to 25 psi. As measured by a differential gage.