Need some tire help

[Superduty Mike]

I have a 2016 F-250 with the FX4 Package. I currently have a set of XD Badlands wheels which are 20x9 with -12 offset and I am running the stock 275/65/20 Toyo AT II's. I have stock suspension, and I would like to know what is the widest tire I can run on these wheels without a lift or leveling kit. I don't really care about going any taller, just a wider footprint. Any help would be appreciated. Thanks in advance.

 

[02Oilburner]

I have the 20x10 XD Riot wheels with a -24 offset and 315/60/20 Toyo MTs I could not even turn the truck without rubbing REALLY BAD. I had to Trim the wheel wells, get the 2 inch level kit, and the bumper spacer also just to drive the truck on flat ground. It will still rub if I am turning sharp on uneven terrain. Wider tires will require some work or a 4 inch lift.