Wheels and tire combo

[DMAX-HD]

What is the largest wheel and tire combo could I put on my truck without any suspension modifiactions? I have a 2008 2500 HD D/A Extended cab shortbox.

[torque]

Don't go over a 33" tire diameter. I have used 255R8516's on my '02 and 285R7516's on my '07 (LBZ). They are both ~ 33" tires. The 285's are wider and they just tap the fender when I back up and turn at the same time. A friend, with the same tires, has the same problem.