My GT is coming with the standard 235 series tires on the standard 18" rims. What is the widest tire that will fit on that rim and still make a good contact patch? thanks

 

Personally on an 8" that is as big as I would go.
I know you can go bigger (you can do a lot of things), but I would use larger rims.

 

255/45 18 will go, 8.0 is the minimum size rim according to Toyo

 

no drag radials offered in that size from what i've seen. No options for drag radials yet with a 18x8 rim?

 

But you do have a 10 inch wide wheel that matches the OEM wheels for Drag Slicks available http://www.americanmuscle.com/silver...8x10-0511.html

 

Nice looking rims (the chrome looks sweet). Are they the same weight as stock, more, less?

 

If you go with a pair of these for the rear to get bigger tires, will having 235s up front affect anything?

I guess if I have stock 235s up front, is there a limit or best combination for the rears? 275 or 285? Is is a 10" rim option for the back.

 

Not sure about weight, but the fact that you gat more traction it would probably be worth more than you would loose for a few extra pounds

Since there are cars running Pizza cutters on the front with DOT Slicks on the back I think you would be fine with the 235's on the front.
I myself would go with the 285/40 18's. Those 10 inch wheels from AM say Fits Rear Only.

 

They have 18x9's for the front and 18x10's for the rear. The offsets are different too so that the bigger tires on the rear won't stick out. I know a guy with an 06 GT and the aftermarket rims look like **** because the tires stick out about 2 inches on the rear due to the offset being way off.