My other bike was a M1800r with 240 stock tire, I installed a 280 tire in the rim and fit ok.

You can use perfectly the 280 in the stock wheel, but the wheel/tire look with ballon effect. If you install other wheel more bigger, the tire look bigger, logic.

 

I wouldn't run a 280 on a rim designed for a 240. I had to replace my 260 this year while on a trip. HD shop in Reno said they see failures fairly commonly from running a wider tire than the rim is designed for. With mine some of the bands broke and made it so lopsided I couldn't do over 30mph and was shocked it still held air to get me to the dealer. Was pulling away from the rim and almost lost the bead.

 

Not everything than CAN be done should be done. It's actually very critical to run a tire to wide for the rim as it may cause severe damage to the tire. Plus the "balooning" of the tire may cause the tire to touch the top inside of the fender when suspension is compressed. Wrt to safety this is not good advise.