^
It all depends of the wheel's offset. Heck 285 is the widest you can go on the 19x9.5 RTR rims because it has a screwy offset that pushed the tires out instead of inward.
345's on 18x11 widened stockers
http://www.svtperformance.com/forums...shedbeast.html
20x12's widened Supersnakes
http://www.svtperformance.com/forums...-out-back.html