I have a 33" spare and it just barely clears stock bumper and under the 3rd brake light. You may be able to squeeze a 34" tire on there. But, with a large spare, you start to run the risk of breaking the spot welds on the rear tailgate. My spare weights 95 lbs so I installed the heavy duty hinges and tailgate reinforcement assembly sold by Retrofit Offroad. A lot of people that have a larger than stock spare tire use the Terraflex heavy duty hinge or the new Rugged Ridge heavy duty hinge. This moves the heavy spare tire load to the body and off on the tailgate.