A gauge for measuring non-skid tread depth and sidewall bulge/indentation includes a gauge body having a spaced apart tire-engaging lower legs and a guide slot extending along the body. Non-skid and bulge scales are provided along opposite sides of the guide slot and a reciprocally sliding slide member is mounted to reciprocally move within the guide slot. The slide member has scale indicia and a tire-engaging probe tip that extends between the spaced apart body legs. The probe tip is extended by the slide member until brought into engagement with a portion of the tire to be measured. A reading is visually made by noting alignment between the slide member indicia and the non-skid or bulge scales opposite thereto. The gauge may operate alternatively as a dual function gauge for measurement of sidewall bulge (or indentation) and tire non-skid tread depth.