I'm looking at putting some 18's on the car, and am getting some mixed answers about what size to use. Some tell me 225/40/18, some tell me 235/40/18. Is there that much of a difference? I have no clue what these numbers mean other than 18. I just want to get as close to the OD as possible for the stock 16's.
Also, has anyone had any past use with Nexen tires? Are they good, just ok, terrible?

Stock
215/55R16=25.3" diameter

225/40R18=25.1" diameter -.9% differance
235/40R18=25.4" diameter .4% differance

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=33

Nexen is a low cost budget tire. Not bad for the price, but for a few extra dollars you could do alot better.

I recently put on 18's on mine I went with the factory size 225/45ZR18. I am trying Toyo Proxes4. been happy with so far. I have always been a Goodyear fan. I do not much about the Nexan.

Good Luck

225/45/18 is the stock SS size.