I'm going to a 18x9" rim all the way around my 2006 GT with a +36mm offset. Will a 275/40-18 size tire fit and still turn ok up front? The car isn't lowered, but I may lower it in the future (Steeda drop - only 7/8" up front, 1 1/4" in the rear).

The 275/40-18 is slightly smaller than the stock tire (27.6" verson 27.2"). Will this make a difference other than a slight speedo variance?

The Kumho tire I would get is the ECSTA SPT with a 320/AA/A rating.

Thanks for any comments and/or suggestions!

I have seen it done several times, and I've seen 285's on 10" rims on the front. You'll be fine.