So I have 18in champion RG5's (car came with 235/40 on front and 285/35 on rear)

The fronts are 8.5in wide and the rears are 11in wide.

I am needing to buy pretty soon.

Are there recommended sizes for this set-up?

I really feel like the rear needs a hair more width, it's not stretched by any means, but it doesn't have nearly the whee protection the front has.

 

Factory rears are 295/30 for 18".

Many others here run either 305 or 315 rears. Check the wheel offset for proper fitment.

 

you can safely run the 315/30 which'll give ya about .8 inch wider. but you *might* need to roll your fenders. it's well worth it.
stay w the 235/40 front.

 

I ran those sizes for quite a while because I went with all season tires in the winter..But now I run 295/35/18 and 245/40/18 Conti's which do me good ...My car does ride great ,, pot hole protection, I have more front lip clearance and I can change my oil easier...

 

this is a daily driver if that changes anyones thoughts.

The 305's don't seem to be available.

 

I run 315/30's and 235/40 on 18's, 8" in front, 11" in rear, lowered with H&R springs. No rubbing issues.

 

I've run:

295/30-19 w 225/40-18 -stock size, stock rims, stock everything

315/30-18 with 235/40-18 on stock rims, stock suspension. Those are "GT2 stock sizes". no fender rolling

315/30-18 with 265/35-18 9" and 11.5" rims, no fender rolling, Motons, lwoered to Gt2 heights. Slight rub on front at full lock ("hey doc it hurts when I do this. So....")


I am pretty sure there there are no 265/35s that work on an 8.5 rim, so you will be maxed with the 235/40.

All michelin PS2s

 

With stock suspension/height 245/40/18 will work also