I think you might be right on the tires. I had factory spec P235-16 r70's on the old truck. This one came(used) with 10 ply LT 245-16 R75's M&S which has both larger OD diameter and more rolling resistance as a fatter tire and more aggressive grip. They are Woosung tires which is a Korean knock off of the Hankook. The old truck tires were Brigstones.