I have a 2003 g35 sedan. I want to put some 20 rims on it. How wide can I go without rolling the rear fender? I was thinking about going 8.5 in front and in back?

I am doing 8.5 with 20's and no rubbing. The offset is what is important

I'm not sure how relevant this is but I was recently at one of those sites where you can build a wheel/tire packages and the recommended rear size for a 19 inch rim was 9.5" with with a 265(!) section tire. That seems pretty f'ing wide to me.

You can actually go anywhere from 255 to 275 on a 9.5" rim most of us are using 275 go which which ever size is cheaper.

Not at all I had a 275/30 on my 8.5 M45s.

Go 8.5 F/R if you want to be able to rotate them. You can go up to a 9.5" in the rear without rolling your fenders if you go with a high enough offset. The Volks on my car (that I will be selling soon ) would fit without rolling. They are 8.5 +39 F and 9.5 +47 R.

^Wish I had money for your Volks

i have an 06 sedan with 350z h-techs...19 x 10 in the rears with 275/30's without my fenders rolled and it doesnt rub at all.....