Tires: maintaining proper tire pressure at high altitude, Tire Pressure

Question
Mr. Smith:

If my automotive tires are set to 32 p.s.i. at sea level, I understand that my tire pressure gauge will read about 35 p.s.i. at 6,000 feet above sea level.  I read that the basis for this is that tire pressure gauges read pressure relative to ambient pressure - if ambient pressure drops about 3 p.s.i. at 6,000 ft above sea level, then the tire gauge pressure reading will be 3 p.s.i. higher (this is, of course, assuming that the readings are made at the same temperature).  Is this true, and, if so, when I am checking my tire pressure for proper inflation, should I make sure that my tires are at 35 p.s.i. at the 6,000 ft. elevation in order to maintain proper inflation, assuming they were 32 p.s.i. at sea level?  

Thank you very much for your help.

Answer
John,

Yes, this is true, but you have to consider that the temperature is likely to drop as you go up in elevation - and the temperature will probably drop faster than the elevation rises.

So for practical purposes, a run into the mountains should call for a few psi higher to account for the temperature.

But inflation pressure is not a particularly sensitive issue for a tire - except to say that low pressure can generate some durability problems.  So being a few psi over would not be worth adjusting for - but may a few psi low would.

And just to clarify - the proper pressure for a tire remains the same regardless of the temperature and altitude.  It should not be adjusted for use at different conditions = except to say that if you move from one set of conditions to another, you should adjust the pressure for the current conditions - and perhaps anticipate the change before you move.