I have been trying to decide what size tires to put on my truck. I have a 2011 F250 c/c with stock 18" wheels. The truck seems to sit level and I have air bags in the back. I don't want to lift the truck just want to fill up the wheel wells and get a more aggressive tire and different rims. What is the biggest I can go with without rubbing? I stopped at a local 4x4 shop the other day and all they did was push a lift, but they did mention that the super duty has alignment issues with bigger tires and that I would need to change something in the front end to get it back to proper alignment.