i dont know much about the offset sizing, just looking for a quick answer... thanks
....I run 245/35/18's without any problems on my 18x8.5 +45 gramlights..
You will be fine as long as you aren't slammed (I guess anything over a 2 inch drop)
You DO NOT want to get 245/40....
One reason is that it probably won't fit
Another reason is the HUGE difference in diameter compared to your stock tire
Anything over a 3% difference is a NO-NO (it will throw off speedo too much, may cause brake failure, etc)
check it out bro
The first to the left is the stock tire off of an 05+ type S....If you go 245 you will need to get a 35 profile due to the little difference in diameter
ooo and heres a pic of my setup just for reference