I took an old inherited set of classic Beachwheels apart to check the bearings (nylon rods) because they were "rumbling" and not pushing well under a bigger cat.
The bearings were rusty brown but looked OK. However, the inner sleeve inside each wheel was rusted all to heck, with big lumps of rust. Curious- a steel tube inside that was originally apparently bonded to the rubber tire! Really.
Well, now its a mess, and the tire leaks too.

Suggestion? Sand, wire brush, paint, add plastic liner?
PS- Like Good Ol' Rick White, I never throw anything away!