I have 14 inch tires on the Passport. They are the new Carlisle tires.
These one are rated to 81 mph. I don't go over 65. In fact here in Wa state the posted speed limit for Trucks is what people towing trailers with a combined weight of over 10,000lbs are supposed to be going.
When I bought my truck it had Hercules tires on it. Metric type, just shy of a load range E. They are 10 ply. I have to say I have about 25,000 miles on them and they are one of the best tires I have owned. I was nervous at first, but I would get another set in a heartbeat.