I have G35C with stock 18inch rims(7spokes)
I am trying to get new rims with 18x8.5front and 18x9.5 for rear.
I was wondering if my stock tires(goodyear) could fit on my new wheels. OR do i have to get new tires that fits on my new wheels??

 

I'm not sure what size tires you have (guessing 225/45R18 and 245/45R18) and I don't know which Goodyears come on the Coupe. I thought all Coupes with 18" rims got Michelin Pilot Sport tires.

Check the tire manufacturer's website, look up your tire model, and view the specs for that size tire. It will list a minimum, recommended, and maximum rim width.

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

All 18" Gs did and do come with Michelin Pilot Sports. Goodyear all Seasons come with the 17" wheel. I'm upgrading my 18" wheels to Nismos now, and I elected to get new tires (Dunlop SP9000s - 245/40 & 275/40). If you look at the tire charts they will say that the stock sizes won't fit on the new (8.5" and 9.5" rims) however, I've heard of it being done.

Lou