Remember that pressure needs to be checked COLD. Air expands as it is heated as we all know.A tire that reads 35 psi cold may well read 40 psi after the air inside has warmed. So if you're checking and comparing with other guages do it "back to back". I too prefer the pencil guages as they are simple, inexpensive and accurate in my experience. I carry one in the tankbag at all times.