After measuring up and hoping, I have successfully fitted 245 width tyres on my car on 8.5" wide rims.
The arches are rolled and with the +35 offset wheels, there is sufficient clearance on both sides of the tyre. Even with my car heavily lowered there is no rubbing and the car now has a much more serious stance, as well as having noticeably more grip when cornering hard.
I recommend Falken FK452s - super tyres, grippy, good looking and quiet.
A 255 will fit on the rear with rolled arches, either if you don't have arch extensions, or if so, if you get them shaved a little, but 245 is the max on the front.
Cheers!
Mart.