Use rods, and I would suggest not using all-thread rod like he did.
And for God's sake, and anybodies ankles, cut off the danged rod.
I didn't see this guys shoes, but I'd bet they are Velcro closed.
I would use solid (not pneumatic) tires. Solid wheels never get a flat tire.

Pick your poison...
https://www.harborfreight.com/material-handling/solid-flat-free-tires.html
Axel rods at the big box stores in the Hardware isle. Hollow steel tubing. Or solid rod, drill and cotter pin.
If
threaded rod suits you, use Nylon locking nuts. Not regular nuts, for positioning/spacing.
And spacers made from Bushings, or tubing that fits your rod size.
Make it Mo Better!