I'm getting ready for a big trip so I just checked my tire pressure with a digital gauge. They were all low, so I added air to get them to the proper pressure (the inflation tool I use on my compressor has a built-in gauge). Then I rechecked with the digital gauge. They were all 3 pounds high! I pulled out the old-fashioned analog spring pressure gauge, and it said they were all about a pound low. So I got a gauge out of one of the other cars, and it showed they were all 2.5 pounds low! Between 4 gauges I had a range of 5.5 pounds! Now I don't know if the pressure is high or low or just right. I'm not happy at this moment.

I blame the Chinese. Does anyone know where to buy a high-quality American made tire pressure gauge?

 

Reverend, I wish you were closer to me. I would bring home one of the pressure gauges from work and we could get you to within 0.05%. As for finding a high accuracy tire pressure gauge, I will venture to guess you will end up creating one yourself. Look up what are called "heise gauges". Heise is a high accuracy pressure gauge company. From there you can adapt a hose using a 1/4" NPT fitting to the gauge (1/4" or 3/8" pipe fitting). A lot of the tire stem pieces for adding air use a 1/4" NPT female end. So, the adapting will be pretty easy.

If you look on E-bay, there are a few Heise gauges there. But, most of them are 10-12" in diameter. So, probably a little bit bigger than what you would want in your glovebox or even to simply walk up to your car with. Ideally, you would want to find a 0-60 PSI 6" diameter gauge. That will be nice to hold in your hand, yet will have the accuracy you are looking for and also be fairly easy to read. But, plan on spending about $100 on just the gauge.

If you want to know more, let me know. I work with these gauges all the time since I am doing calibrations of various air, hydraulic, and electronic system components. So, this is what I work with day in/day out.

 

While I have digital and analog (spring) gauges I measure correct pressure more by keeping an eye on the tire wear. Too much center wear, too much pressure. To much edge wear too little pressure.

The best wear point has turned out to be 28 psi on a Craftsman digital gauge but who knows what the absolutely correct Naval Observatory pressure really is.

 

I have the little "pen gauge" type, where you press one end on the valve and a piston shoots out and you read off on the side of the piston. Apparently these are very accurate, unlike the usual gauges. However, I was also told to make sure one is within 10% of the stated value, and, most important, that the tyres on each axle are the same pressure.

On my 2003 XJ6, there is a "normal" setting, and a " Comfort" setting about 6 psi less than the normal, (which allows cruise at maximum speed, whereas Comfort is for up to 100 mph)