The Pirelli MT-21 front tire was worn out and the rear Shinko 705 was just too street oriented for the kind of riding I plan on doing this summer so I swapped them out for a set of Dunlop D606 knobbies. The big difference is with the front D606 being directional versus the omni-directional MT-21. Street grip seems to be the same but the D606 vastly out performs the Mt-21.
