Actually, in a general sense, 205's on 7" is fine. add .5" for every 10 mm, and you're safe, i.e. 215 on 7.5, 225 on 8, 235 on 8.5, etc...
The tire mfg's site will give you accepted wheel widths for the size tire you want.
I've had 225's on 8.5" wheels, and the rim was outside of the wheel. My S-Runner has 235's on 6.5" wide wheels, and looks HORRIBLE.. All ******* looking...