A 225 section tire is 8.86" wide so mounting it on a 9" wheel is fine. Also, as you get into lower sidewall ratios you have less angularity between the contact patch and the wheel width, that's why really tall sidewalls have narrow wheels. My Sentra came with 185 (7.3") on 5.5" wheels because it had a 65 series sidewall. Meanwhile the 245 on the Z (9.6") mounts on a 8.5" wheel because it's side wall is 110mm vs the Sentras 120mm and it's more of a performance application. By similar virtue I replaced the 185/65/14s (7.3"/120mm on 5.5" wheel) with 205/50/15s (8.1"/102mm on a 7" wheel). If there is a specific point at which the sidewall height/ratio needs to go over to a slightly larger wheel than tire I don't know but either way, the sidewalls on the Lambo are almost vertical anyway.