One thing to keep in mind when sizing tires for "spirited" driving (autocross, road racing, etc...) is that wider is not always better. The width of the tires need to be matched to the width of the wheels.
A good rule of thumb is that the wheel width needs to be within a certain percentage of the tire's section width:
70% - regular street driving
80% - "spirited" street driving
90% - hard-core handling (autocrossing, road racing, etc...)
So, for the following tires:
Width | 100% | 90% | 80% | 70% |
285 | 11" | 10" | 9" | 8" |
275 | 11" | 10" | 9" | 8" |
265 | 10" | 9" | 8" | 7" |
255 | 10" | 9" | 8" | 7" |
245 | 10" | 9" | 8" | 7" |
235 | 9" | 8" | 7" | 6" |
225 | 9" | 8" | 7" | 6" |
215 | 8" | 7" | 6" | 6" |