I made mine. Accurate to within 1 psi. I bought a plumber's pressure gauge from Ace hardware. I had all the fitting at home. I can use it to air down, too.

 

I will no longer use mechanical tire guages. I had a "quality" one similar to the Longacre and noticed after a few years it was off by about 4psi compared to every other gauge.

I've had great luck with the $10 cheapies like the Victor from Walmart or Autozone. I've owned 3 or 4 of them of different brands and they all read within 1/2 lb of each other and the other guages I've compared them to...

 

I use two of them.


I use the Griot's one above to air down (pull the trigger half way) and it can be used to air down whether it's hooked up to my Power Tank or not.

I then check for better accuracy after inflating with a digital gauge.
I run about 35 PSI for street pressure, gives me a tad higher MPG.

 

The problem with those cheap pressure gauges is that they are very inaccurate and imprecise at lower pressures. I wouldn't trust them below 20psi and when you get down to 10psi and lower you need to know exactly what pressure you're running so you don't blow a bead.

I made my own from parts from mcmastercarr. I have two guages, one for street pressures and one for 1-15psi. They're rated for 2% accuracy and the whole thing only cost $20.