A self-inflating tire assembly includes an air tube mounted within a tire sidewall groove. The air tube is in contacting engagement with opposite angled groove surfaces surrounding the air tube. A segment of the air tube is flattened from an expanded diameter to a flat diameter by bending and compression of the groove in a rolling tire footprint to force air evacuated from the flattened segment along a tube air passageway. A tube is positioned within the groove, wherein the tube has a circular cross-sectional shape and an outside diameter D, and the groove does not have a circular cross-sectional shape, wherein said groove has a width W and a length L, wherein D is greater than W.