Replace tires or both rims and tires?

[jeff57]

Good morning forum members,
I would like to ask you folks for some feedback, insights, info, etc. about replacing the tires on my camper.
Currently my camper has ST205/75R14C original/stock tires on it, which I think are undersized. We purchased the camper new in Sept. 2016, date code on tires is 2016 (not sure off hand what week), the GVWR of my camper is 7500. I am going to replace the tires this spring but am wondering if I should just replace the tires with LRD or go with new rims and tires for even more "margin". I don't intend to carry more items in the camper, just would like to feel more comfortable with the tires and their capacity. I also have a TPMS.
If I go with new rims and tires, would it be better to move up to 15" rims or stay with 14"? There is plenty of room for the 15" rims.
Our camper is always on the move during camping season (not at a seasonal campground), probably putting on 3500+ miles each year.
Any thoughts or other things that I should consider?

Thanks in advance!