Going to depend on the brand as well. A nitto 315 will fit on a 9 inch rim and not bulge too bad. But a BFG 315 will look like ass on a 9 inch rim. I run a 295-35-18 bfg drag radial on a 9.5 inch rim and it looks pretty good.
I have some 19/9.5's with 285/35. They still look like pizza cutters! How big can I go for some extra width? Sorry I'm not trying to highjack the thread.
I run the 315/35/17 BFG drag radial on my 17X9" wheels and it looks good to me. I think it evens the car out lookin down the side of it. With the factory 275's on the rear the tire sets inside the fender well too much IMO. Like I said just my Opinion.... :shrug:
315 nitto may fit on a 9", but a 315 BFG should without a doubt be on a 10 or 10 1/2 " wheel. I currently have a 285 BFG on a 10" wheel and its a perfect fit!
A 275 is the ideal size for a 9" rim from a 'lateral acceleration' point of view. There is no 'bulge' and the sidewall comes right to the edge of the bead. If you like to carve the 'curvies' I would stay with that size. A 285 and even a 295 may fit but you will get some sidewall 'shrug' under hard cornering. Just my two cents for what it is worth. I have 275/35/18 on all four corners and with the suspension mods it is a pretty well balanced car (relatively speaking).