Sorry, I'm completely lost here.. So, actually, I have 236/65R18, so 30 inches diameter (6 sidewall) and 9.3 wide. I you see on my last picture, It seems that the my limit is more the sidewall size than the wide ? If I go with 255/70, it is 32.1 diameter (7 sidewall) with 10 wide. So, I have +1 inch...