When you shop for a bike carrier, check to see if it disallows use with a RV. Many if not most, do.
I have destroyed two different racks. The Swagman was the only brand I could find that stipulated it was OK with a RV. Mine is 9 years old and as solid as the day I installed it.
Then there's the bumper. Inmost cases they aren't strong enough to hold a rack. My bike rack nearly ripped my bumper completely off.
They need to be reinforced. (A spare tire is nothing like a bike carrier so don't think you'll be fine because of that)