When you add to the width you are increasing the foot print of the rubber on the road. If your not racing or looking for land speed records the added resistance will be minimal but this is just my opinion.
I recently went with beefier rear AND front tires. Steering hasn't change enough for me to really notice a difference due to the front change in width and hight the rear feels the same for me (On an Adventurer). My reasoning was simply to get fat white walls on my ride, I personally like the look.
You also will decrease the clearance in your wheel well. An example is that I can no longer use a front fender without it being modified because my front wheel is fatter. The rear typically has more clearance so I don't think that's going to be an issue for you although your going to want to take a hard close look at life with an extra inch around.
Keep in mind when you ride your tires expand a bit too.
Good luck!
Tre900
Pictures of tires, exhaust mod's on 97 Triumph Adventurer
Linear Mode
