Originally Posted by John E

On a road bike, tread direction (or even its absence, depth, or preslence) makes no difference, because the tyre is too narrow to hydroplane. (The road contact strips of my 23mm Conti Ultra-2000s have been essentially bald for several months.) If you ride on severely crowned roads, you may want to swap the orientation of each tyre periodically to equalize wear across its road contact surface.