I'm at 285/70/18s - 33.75" x 11 x 18s. They rubbed the rear of the front fender well liners pretty bad and I had to bang on the front of the rear fenderwells.
Correction: I have 275x70x18s, not 285x70x18s.
I still have my 32.75" spare - if I ever need to use it I'll over inflate the spare and under inflate the 33.75" tires to approximate the same height.