Tires: Up size front tires on a doulie, ford 350, tire size

Question
My truck a 2000 Ford 350 doulie came with 235/85R 16 tires. I want to upsize the front tires using the original wheels. What is the next larger tire size.

Answer
I'm sorry to tell you this, but the original rims are not wide enough to accommodate a larger size.  While you can physically get a larger tire on there, the tread will "arch" and that causes the vehicle to have vague steering and might cause the vehicle to "wander".