I bought a set of Big O Big Foot Tires. These have a 3 year replacement guarantee and a 60,000 mile prorated guarantee. They have been a good road tire though a bit noisier than the rugged trails that came with my X. These are excellent off road and in the snow. They are also $1000 for a set of 4, but I got mine on sale for $800. You might check around and see if they are on sale.