philthetrill
01-07-2014, 11:19 PM
"Significant changes in altitude affects tire pressures when traveling from one elevation to another. Fortunately this influence is relatively small and can be easily accommodated. Atmospheric pressure is the force exerted on objects by the weight of the air molecules above them. While air molecules are invisible, they have mass and occupy space. However as altitude increases, atmospheric pressure decreases. For example, atmospheric pressure pushes against the earth at 14.7 pounds per square inch (1 kilogram per square centimeter) at sea level, yet drops to only 10.1 pounds per square inch at 10,000 feet as indicated in the following chart.
Altitude (ft.) Air Pressure (psi)
Sea Level ....... 14.7
1,000 .............14.2
2,000 ............ 13.7
3,000 .............13.2
4,000 .............12.7
5,000 .............12.2
6,000 .............11.7
7,000 .............11.3
8,000 .............10.9
9,000 .............10.5
10,000 ...........10.1
When it comes to measuring tire inflation pressure, it is important to realize there is a difference between atmospheric pressure and gauge pressure. Most pressure gauges (including all tire pressure gauges) are designed to measure the amount of pressure above the ambient atmospheric pressure
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=167
Altitude (ft.) Air Pressure (psi)
Sea Level ....... 14.7
1,000 .............14.2
2,000 ............ 13.7
3,000 .............13.2
4,000 .............12.7
5,000 .............12.2
6,000 .............11.7
7,000 .............11.3
8,000 .............10.9
9,000 .............10.5
10,000 ...........10.1
When it comes to measuring tire inflation pressure, it is important to realize there is a difference between atmospheric pressure and gauge pressure. Most pressure gauges (including all tire pressure gauges) are designed to measure the amount of pressure above the ambient atmospheric pressure
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=167