I stuck my finger past the rear wheel and noticed there is only like an inch gap between the inside side of the tire and the wheel well wall. How can you put wider tires on the '05 with this in the way?

Also what's the max size (circumference) that it can take?

 

Not sure what the max is that can be used.....but if you have an inch wider tire, it's only 1/2 inch wider on each inside/outside. So, if there's an inch gap there now before the tire touches the inner wall, then all should be fine.....I think???

 

Tire rack shows a 19"x10" and a 20"x9.5 rim for the Mustang GT. Pretty stout puppies.