Originally Posted by MarksM
Offsets are 44 front 25 rear, no spacers.
Aren't those the 18x8.5 TR Motorsports wheels?
I thought you were running 18x10 ET25 on all four corners (an awesome combination, if it fits), and just questioning what tire sizes to use?.
Personally, If I had a set of the TR Motorsports wheels in 18x10 ET25, I'd be running Hoosier R6 tires in 275/35-18 on all four corners. Temps, camber and pressures aside, I think that would yield your fastest laps. Probably only get a weekend or two out of a set, though. Fronts might be camber challenged. I wonder of GC will have camber plates out soon for this car.
If tire wear is an issue, I'd consider the Michelin PSCs, 285/30-18 again in a square set-up. They would be less sensitive to camber settings, too.
Back to your original question, if you want to go wider in the rear, you are going to need wider wheels as well. Eleven inches wide seems right if you are going to 305 mm tire. Your wheel selection gets pretty slim at that width. You might have to go to a custom made wheel like Fikse for that.