I have a 2015 GT with A set of Te-37 is SLs I just bought for it and I'm trying to decide what tire to run in the front. Original I was thinking a 255 but I don't want that stupid stretch but I'm scared of throwing something on that's way too big. A guy in town with a 2015 runs a 20x11 rear with 315s and a 20x9 front with 255s. Has anyone had issues with running a 265/40 tire up front on a 10.5in wheel?

 

Also the offset of the wheels are +21

 

I run a 265 35 20 on a 9" front no issues. Car is lowered an 1". A 265 tire on a 10.5" wheel would still be stretched. I have a 305 30 20 on my rear 10.5" wheel which fits perfect. Look and see what the GT350 has on the front and you should be fine with that.

 

The GT350 runs 295's on 10.5" front and 305's on 11" rear, but that will not fit on a regular GT, as the 350 has special front fenders that are wider to help fit those tires.
I for one think 10.5" rims on the front of a GT are just to wide, even 10" is pushing it.