Tried 30 x 20 today on the Alfine 8 29er. I've got to say that it was a nice improvement over the 32 X 19 I was running over the last few years. My bottom is 6.1 mph at 90 rpm with the top hitting 18.8. Perfect for our southern Ontario trails which generally aren't super steep. If there is really steep stuff it tends to be very short. Of course I ran out of gears on the road going home but who cares about that.