I had 255/40. No problem. Went to Pole Postion 265/40-17. Dealer spent 3 hours to get them on. They had to use one machine to take off the 255's and a different machine to put the 265's on. They tore the bead on one tire that went flat in 3 hours. Had to go to NTW (only place open). They sealed the bead with bead sealer, and gouged the rim in four spots.
Now the fight begins.
Lesson learned stick with my BMW dealer and stick with 255/40-17 in the rear and 235/45-17 in the front.