Atmospheric pressure affects most all tire pressure gauges regardless of type, quality or what you paid. The only exception is an “absolute pressure reading-gauge” and I’m willing to bet money, marbles or chalk that no one out there has a tire pressure gauge that reads absolute (tire) pressure. However, if you have an altimeter, it reads absolute pressure. This is PSIA to the pressure geeks. All of our tire gauges read PSIG or “gauge” pressure. That shows tire pressure relative to atmospheric pressure. Don’t believe it? Read on! By the way, for around $150 you can get a PSIA tire gauge just like the NASCAR guys use.

Some folks tend to treat tire pressure like a newborn baby but are totally unaware of the effects of elevation and temperature. This page addresses what altitude does to tire pressure gauge readings. Read about temperature effects on tire pressure and gauges here.

This contraption, in effect, puts several different kinds of gauge mechanisms in a peanut jar “altitude chamber”. Both front and back views show the different types of gauges; primarily, the Bourdon tube, bellows and pencil mechanisms. Using my shop vacuum at “V”, I could vary the altitude and see the effects on tire gauges. It compares the effects on gauges at two different altitudes at one time. I measured altitude with an analog, bellows-type altimeter inside the chamber (not shown). The chamber is best explained with the aid of this schematic.

There are five gauges total attached to the chamber. The A gauge is completely outside the chamber and represents a tire gauge working in an open environment as we normally use tire gauges. It reads the pressure on the manifold, M. The input ends of gauges B and C are outside the chamber; however, their mechanisms are inside. B is my super low pressure inflatable boat pencil gauge, and C is a low-pressure bellows dial gauge bought specifically for this test. B and C “see” the simulated elevation change on their mechanisms with or without pressure at the input end. Two more gauges were arranged with their input ends attached to manifold M. D is a conventional pencil gauge and E is a Bourdon tube dial gauge. Note that their mechanisms are inside the chamber, so they see the simulated elevation change. V is the vacuum connection that achieves an “elevation” change.

Using my shop vac, I could take the chamber from sea level (about where I live) up to 9,000 feet elevation or about 10.51 psi and the nut jar chamber survived perfectly! The altimeter mentioned above confirmed the elevation. With no pressure on the manifold or any of the gauges, B, C, D and E all rose as I drew a vacuum because their mechanisms were inside and they saw the decreased atmospheric pressure. If I could have pulled a perfect vacuum, they would have measured 14.7 psi or atmospheric pressure at sea level. This confirmed that gauges are affected by atmospheric pressure.

With the chamber at sea level (same inside and outside pressure), I pressurized the manifold M and A, D and E showed the increased pressure. I then dropped the chamber pressure (increased the elevation) and D and E showed an increase in pressure, but A showed no change. This again confirmed that gauges read more at higher elevations than at lower elevations on an unchanged tire (pressure). I should add that all gauges were working normally. They were responding to atmospheric pressure as exactly as a PSIG should. This link takes you to the Gauge/Altitude Compensation page where you can see what pressure change to expect with a change in elevation.