Harley-D did convert to a wider tire on some of their models. The Night Train and some of the Dyna's are running a stock 170 or 180 rear for 2006. I do not think you can go much wider without some major mods on our bikes, SM/BA. Take a careful look at the clearences in and around the swing arm area. It is real close in some places.Good luck in your quest. Vegas
