The early (pre-war) fighters nearly always had the smooth tires as you see here. I'm not certain when the treaded designs started to appear, but it was after the particular Hawk I'm building. My thinking is that almost all prewar airfields had proper grass landing areas and smooth tires are most efficient when flying off of grass. The treaded tire types in the U.S. were developed for hard surfaces, dirt runways, and pierced steel planking and started showing up on heavier airplanes first, then moving to the lighter types. The Navy and Marine Corps also switched to various tread types for their own reasons.
