I can mount the 5″ dia tires by hand, and dismount with the addition of a single tyre iron, usually. I spray the bead and rim with wd-40 and inflate to around 60psi to seat bead and immediately relieve pressure after both sides !!POP!!
6″ tires, well, they’re a pain.
Incidentally, I’ve noticed that I can seat beads much more easily with the valve stem cores in….wonder why?