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.
FAA certified jet engine and aircraft technician,
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41 years karting experience