Padle tires are mainly used on off road vehicles, specifically designed for use in sand. They consist of a smooth tire core which has a series of large rubber cups (or paddles) attached to it. The volume inside of a paddle is much larger than the void of a knobby tire, so it is unlikely to clog up with sand. The paddle provides superior traction in the sand, in part, because the paddles dig into the sand and push off from the buried sand, not just the surface.