Do they make 5″ tires? All I found was 6″ tires that needed chemicals and cooking to make them work. Also they are low rubber like a tire that’s been cut down.
Looks like the 5″ tire sets have 3.60″ fronts. Might be interesting to try on a clone kart. They have a 4.50 but in a different compound with no rear tires and the UN-515 looks to be something for the vintage karts. The other tires on that page are 6″.
I hope that max inflation number is the recommended running max, it would be hard to bead a tire at 20psi.