A Funny Thing Happened on the Way to Alaska

[WyoJim]

And again in Pennsylvania.



I aired my rear tires up to 80 pounds before leaving for AK and upon checking them in Valdez, found them to be an even 60 pounds. Both of them.



I aired them to 80 again to go to PA and in PA found them both to be 72 pounds.



All airing and checking was done cold and the only answer I can come up with is the difference in elevation. Almost 5000 feet where I live, Sea level in Valdez, and about 1200 ft in PA.

Ambient air temps might also affect the problem. Warm here, cold in Valdez in September and cold in PA in May.



Between these trips we went to AZ. I didn't check them in AZ. But in mentioning this to my wife she said that when we left for AZ she had a half can of hair spray but when she tried to use it in Phoenix it was empty.



Any better theories than elevation and temperature?

 

[DIESELMAN]

Tire pressure increases about 1psig for each 10 degrees F increase. So running 100 miles loaded can raise the temp by 100 degrees easily, increasing 10psi.



Changing from sea level to 5000' amsl decreases the outside air pressure by about 2psi, but that causes the tire gauge, if the temp is the same in both locations, to read 2psi HIGHER, relative to the outside pressure. In other words 80 psi means the air pressure is 80 psi greater than the pressure outside the tire, and reducing the pressure outside the tire by increasing elevation, increases the internal tire pressure relative to the outside pressure.



decreasing temp / lower elevation = lower psi



..... or you have a leak...

 

[KKaiser]

..... or you have a leak...





And two nice, even leaks at that!



KK

 

[Prairie Dog]

Great, all this talk about leaks and... I'll be rite back.

 

[Ron Bissett]

loss of psi?

Check valve core or stem for loose core and or a crack in stem . Had a stem that would take air after going down and hold air until the stem was bent over then air would rush out ,air it up and it would seem to hold . Ron Bissett in Metro Louisville KY