Zee A.

So I've tried searching and haven't really gotten my answer to my question. I have a 2018 GMC Sierra SLT 4x4 with 20inch stock wheels with a 2.5 inch leveling kit on the front. Its time for me to get new tires from the ones i drove off the lot with, I wanted to know what the biggest tire i can run on my truck with out rubbing. Some forums says 33x12.5x20 should be fine with no rubbing but some say otherwise. Is anyone else running a setup like this and can advise that this will work on STOCK 20's. Or what recommendations you have for bulkier rubber?