The option GT wheels are 17x8" wheels. My GT came with the *beloved* Tri-Bar 17" wheels. The stock tires were a 245/45R17. I currently run 275/40R17 on 17x9" wheels and I think they are a good fit. I would think that 275's would undesireably bulge on a 8" wide wheel. IMO, I wouldn't run any wider than 255's maybe 265's on a 8" wide wheel.