Most of my bikes (about 50 of the 70 some) are hung on display and while a low tire sags a bit, the majority of visitors appreciate seeing the bikes, and only once in a while alert me to a low tire and it's usually informative instead of criticism. For scooters like some of my Cushmans, Doodlebug, Salsbury, and some of the smaller cycles, I cut a wooden block about a 4"x 6" or so shimmed to barely let the tires touch the floor when placed under the frame in the vicinity of the motor/transmission area. The machine is then safely balanced vertically instead of leaning. I agree w/ scrubbinrims that older tubes hold better. With my older cycles, (over 70 dating back to a 1912 Harley) have to bite the bullet and air at least a cuple of times a year. The clinchers are the worst as if the tire pops out of the clinch groove, it's a real pain to get it back w/ wheel still in the bike. On some of my motorbikes, like Whizzers, Simplex, Smith Motor wheel, etc. I have welded about a 5 or 6' piece of 3" channel iron atop a desired length of 2 1/2" pipe on a substantial stand and welded a notched or drilled flat iron piece on each side of channel when placed under the front and rear axles keep weight of the tire. These stands between some of my cycles save floor space. I'm having trouble posting photos, but you might see some of our collection on
www.miracleofamericamuseum.org.