Hey, been a while since Ive been on the forums. Now I find myself in possession of a well equipped F800GS with still a lot to learn about the bike and adventure riding. Excuse the sporadic and possibly newb questions. Just curious about what size/type of tubes Im suppose to buy for the tyres. Im running 90/90 21 on the front and 150/70 17 on the rear. Will be changing over to Heidenau K60s before I head off on a road trip but Ive no idea what size tubes Im supposed to buy. Was looking for something that had the same sizing but the sizing for tubes has left me somewhat confused. Any help would be great.