ahh yes cheap gauges.
Get competition spec.
Kart shops usually only have up to 30psi, which is what I use for deflate offroad pressures.
I use a cheap ARB inflation stem with gauge, and close enough is good enough for the road. I run 40psi plus.
Offroad pressures I am more fussy about.
I usually have to get a balance and wheel alignment after wheeling, so just make the tyre shop I trust get it right.
http://www.revolutionracegear.com.au/index.php?PCID=17706&PSO=245&PSID=3100006000&PSV=Primary&CDO=Remember to recheck when hot, and cold. You will find a sweet spot, and it will be about 36 stone cold.