What size tires do you recommend?

Currently I have 285/70/17 on fuel rims and the truck slings mud like crazy. Tires don’t stick out much but enough to make a mess. I’m not sure the offset of the rim but I’m afraid this is my biggest problem.

 

I jus got 255/80r17 st maxx and really like them. On a first gen but they tuck under pretty nicely

your wheels may be a little wider than recommended

 

Just ordered a set of oversized rokguard mud flaps for it after doing some reading.

 

If the mud slinging is your biggest complaint then your issue is more the wheel offset than anything else. Go with narrower tires and narrower / higher offset wheels to bring your wheel/tire in closer to the body of the truck so less is exposed.

And/or... get some mud flaps.