I've gone through a few pages and didn't see an answer to my question. What is the largest tire size I could put on the 08 FX4 18" rims? Truck is stock, no lifts not leveling kits. The stock BFGs just aren't cuttin it off road

 

Try a 285x65x18 BFG or Nitto AT, close to 33 inches tall.

 

Or a 33x12.50-18.