It all depends what you want to do with your truck. I run 35x12.50r17. I've had m/t's since my oem tires reached half tread. Since my needs have changed, I will be going to "F" rated a/t's. Hybrids actually. People have been raving about the Mickey Thompson Baja Boss A/T's. 50,000 mile warranty. I am probably going from 17" to 20" wheels. I don't like the looks or reduced off-road ability, but it will provide better stability towing. We'll see.