Originally Posted by Leisesturm

I don't know ... I really don't know ... I had a pump with a gauge that could actually tell me how much air was in the tyre in the morning (Joe Blow) but it died. I am acutally using a better level of Topeak floor pump these days and I am hanged if I can get the pump head on without losing (that's how you spell it) 10psi or more in the process! It seems the majority of pump gauges and standalone gauges are like this. You lose a bunch of pressure getting the gauge in place making your reading meaningless.

Once locked onto the valve stem the reading of tire pressure is straightforward on any decent floor pump and since I paid over $120 for it I see no reason to question its accuracy. Sometimes its best to leave well enough alone. My Marathon Plus (26" x 2.0") are 70psi max on the sidewall. I put 60psi in each one and I am good to go for months. Literally months. Maybe years, I don't know. It just bugs me after enough months that my morning pinch tests still return a satisfactory reading and I put some air in. It does annoy me that I can't actually see how much air they lost (if any) between top ups but I am more impressed by the fact that the damn tires NEVER FLAT. They just don't. I mean, I am rolling through crap, daily, that would flat cheap stuff like Kenda Kwest in minutes, and better stuff like 'Big Apple' in days. Maybe weeks for standard Marathon, but ... never? The giddiness never goes away. Bontrager Hardcase H2 are pretty flat resistant as well. Y'all call them garden hose ... I.am.ok.with.that. If this is how garden hose rides, woo hoo. Even if slower than GP5000 the fact that you NEVER lose the time it takes to swap a tube. I don't know, that's got to have an effect on the performance rating. A positive effect on the performance rating. FWIW.

Originally Posted by MikeDeason

I did use a quality gauge, Topeak, and it gave me a bad reading. That’s the gauge I tested against my TPMS to determine that it is defective.

Originally Posted by phughes

TPMS sensors are not always the most accurate, but they are close. A fairly good way to be sure a gauge is correct, or close enough, is to buy two gauges, and check them against each other. If they agree, you can be pretty sure they are good. None will be 100 percent accurate until you spend real money, meaning research grade, but that is pointless. I do buy one good gauge, I buy a dial gauge in the range ideal for my use. I keep that gauge in my tool chest and use it in the garage and driveway. I also buy smaller gauges to use in my motorcycles and cars. I check them all against my good gauge, one I know has been calibrated. If the gauge has a huge range, it will not be as accurate as one that has a narrower range. So if a gauge can measure up to 150 psi, you can generally bet that it isn't too accurate when measuring 20 psi.

Seriously though, it's generally good enough to buy two gauges and check them against themselves. They need to be checked against a known good gauge periodically though because they can go bad, or be damaged.

Originally Posted by PeteHski

I’m wondering if you actually read the first post and understood the OP’s ispecific ssue? My suggestion of checking his brand new suspected faulty Topeak gauge and old track pump gauge against 4 independent TPMS sensors on his car was just an easy way of determining which of his 2 gauges was reading 15 psi off without having to buy another gauge.

Originally Posted by Polaris OBark

Digital gauges have better precision, but that does not entail better accuracy.