We just got a new Thor 23TB Class C, and I was shocked to find it come with NO spare tire, not even has a place for one! Seems like one would be in a tough spot, if one had a tire go bad in the middle of nowhere, w/o a spare!
So I picked me up a steel hitch mounted rack ($32 total price), to carry a spare tire (w/o rim). It was made for off-road 4-wheelers, but has 150 lb. capacity, so it should be fine for carrying a tire.
As shown on our BMW SUV: