At least I find 11 tires read exactly, #12 read like 40#. I wanted 36# so I released some air, rechecked the 40# gauge, blew some more and still read 40#. Went to my cheap battery powered gauge, tire #12 now reads 34.5#! Now I have to go back and check all the tires with a different gauge. !2 tires, 6 on the motorhome, 4 on the towed vehicle and 2 on the tow truck.