As mentioned, the tailgate is capable of 33" tires, but the trick is to keep the tire tight against the bumpers, and do not allow it to move around.
Since I plan to go to 35s, once I wear the current 33s out, I installed an Exogate carrier. This frees me up to install my choice of bumpers, allows me free access to the tailgate, and it actually swings much easier than the stock hinges.