What force keeps a bicycle rim off the ground?
There's a downward force on the rim (transmitted through
the spokes) from weight of the bicycle and rider.
That force is balanced by an upward force on the rim;
what supplies that upward force?
For this puzzle, consider a tire that's tubeless, thin,
lightweight, and inflated to 100 PSI or more. The air
pressure keeps the tire's carcass in tension everywhere.