My tires are 700x45 so not skinny by any means but not super wide like some I've seen. My gauge is a supposedly good gauge from the HD dealer. The highest marking is 60 and the tire reads past the 60 and pegged so I presume that's 65-70 psi. At some point I'll have to get a gauge that reads up to 90 so I can measure on the dial up to the max rating of the tires.