Not if your new tire dimensions are the same as the ones on our car now. The sidewalls are smaller on 18 inch rims. Just find out what tires you plan on getting on the 18's. Then find out their overall diameter.....it will be in the 20's.......like mine are somewhere around 26.5 inches or somewhere around there. (Not exact, just hoping to get you to understand what I am referring to)
Justa look up the subject on the posts search if it still works. There is also a calculator that will give you the exact dimensions just use google and type in tire calculator! I bought the 18x9's cheap on ebay from OEM WHEELS 691.00 I am planning to run 265/35/18's for tires and a few people are running the set up now with no issues speedo or otherwise. He had the speed stars as well! good luck
I dont think they make a 256/35/18, I have 275/35/18 on mine and according to the tire calculator I'm only off like 1 or 2 mph. I would recomend going with a narrower tire up front than in the back(like maybe 255/40/18 in front and 275/40/18 in the back for example)