Depends on many factors and weight of the camper. So we are going to need more information about your camper. What is already on your camper? With popups you really can't change size much as you are limited to what can fit in the wheel well and lug nuts etc. Load range is usually based on the weight of the camper. Radials vrs bias ply can usually be a personal preference and road surface you see yourself on more. Wanted to add, you need to look at ST tires. Regular car or truck tires are not designed for the stress trailer tires face.Hey there fellow campers. Question about tires for our 1997 Fleetwood pop-up; what are the best tires/ size/ brand and trailer or passenger? Looking forward to sharing our adventures. MandY