I like cheap knobby tires. The small lugs ride really well compared to a v-tread or similar with long lugs that don't flex. Just get the cheapest 2 ply knobbies you can find in 22 inches tall and run them at a lower pressure. Should ride really well and go through most terrains you would encounter with a go anywhere rig. For the front, see if you can pick up some 8 inch front rims from a lighter duty garden tractor that has 5/8 inch spindles. They should slide right on. Mine came from a Sabre (made by John Deere), and my knobbies I got off Walmart.com shipped to my local Walmart and installed for 40 bucks each total.