285/75/16 question

How much lift do i need to run 285/75r16 tires ? I have a RE 3 1/2 inch kit with 2 inch spacers in front and the longer lift shackles in the rear. I have a good deal available on some cooper sst's !!! I have 31/10.50r15 on right now with no rubbing.

thanks.

285 x .75 = 213.75 x 2= 427.5/25.4=16.83+16= 32.83" OD, 285 x 25.4=11.22" in width