I am looking for a fat urban assault tire. I need something tough. The Hookworms are a bit cheaper, and also have a lower TPI number (which I was told means stronger tire). Then I read about some Kevlar guard on the Fat Franks...Does anyone know if that's on the road surface? or the sidewall? I am combating goat heads, and most of my issues are riding surface punctures only. Any advice would be rad.