It's like people asking me what fuel mileage my 1991 M931 A2 5 ton 6X6 gets too. I tell them it runs on destroyed hopes and dreams, with a sprinkle of crushed Prius.
Tire brands can REALLY vary in actual size, for their indicated size. Before making the jump to 18, 19, or 20 inch wheels... it would be cheaper and easier to try another brand of tire first.
I'm running the same size rears (285/40/17), but in Nitto 555 on the back of my Mach. You can clearly see it fills my wheel wells better than the same "size" tire you are running.
My rear wheels are 9" wide though, compared to your 9.5 inch wide wheels. So, your tires have more stretch in them, which will also affect the appearance.
I think running a 19 or 20 inch rear wheel will look somewhat cartoon like on your car too. JMHO
Powershift got a reaction from mach1cj in what's the MPG on your 428CJ?
Powershift got a reaction from bullingju0 in yet another wheel/tire thread...