P315's might fit:

[BillyGman]

I've read atleast some of the threads on here which discussed what the widest tires that would possibly fit on the back of the GT500. Perhaps much of this is all guess work at this point since the car isn't even out yet. But from what I remember, it seemed to be the general concensus on this forum that P255's and maybe even P275's would be the widest possible tires that will fit.

Just for a point of interest, I know of someone on the Marauder board who has a 2005 Mustang GT, and he has pics on there of his car that he's put 10.5" wide 20" wheels on the back, and has Continental tires size P315/35/20" w/out even using any spacers either. Now I realize that the suspension of the GT500 will be lower than that of the GT, but this guy has also lowered his car 1.5" in the back, and .75" in the front.

So if he has successfully done this, then maybe we will find that when the GT500 comes out, and some of us purchase them, that we will be able to do the same. I just thought you guys would like to know this. If this is old news, then please pardon my post. But incase it isn't, then here's a link to the thread on the Marauder board which includes pics of this guy's car.His name is Lidio, and he's also one of the best engine tuners I know of.....

http://www.mercurymarauder.net/forums/showthread.php?threadid=18339

 

[Irish351C]

Do you know how much offset his wheels have?

 

[BillyGman]

Do you know how much offset his wheels have?

Hmmm, that's a good question. No I don't know. I know that he offers a wheel widening service, and I had him widen the back wheels on my Marauder, and they turned out real good. Maybe for those of us who do end up getting a GT500, we will need to call or write to him, or have him widen the wheels for us. but I'll see if I can find out the answer to your question in the mean time.