Can i but a 200/55 tire in the back in a 790 duke or no ??
Not sure about the rest of the years but in 2020 track mode came already equipped Just FYIWelcome to the forum.
No point going a wider tire without a wider rim. Then clearance likely will be an issue. On too narrow of a rim, the tire will just be my rounded and you'll end up with even less of a tire contact patch which sort of defeats the purpose of a wider tire in the first place.
If just for looks, well that is your call. Did you do the extension for looks or to try and tame the wheelies (assuming you have the track pack and have the race mode enabled)? Didn't know anyone made extensions for the 790 and would have never thought there was a demand for them.