I have to take the plunge for new tires soon. I'm considering B.F. Goodrich M/T's size 32x11.50 - 15. I have 15-10 rims ( from my long gone F-150) with 33 x12.50's on now. I don't know the offset on these rims but I think that they will be a little wide for the new tire and they now rub the springs on sharp turns. I'd like to go with a 15x8 rim and would like to get an idea on what the proper backspacing should be. Thanks for the help.