Stupid stuff you learn whilst bored in your man cave.
A 4.80/4.00-8 wheelbarrow tyre fits a kids bikes 12 x 1&1/2" wheel. Result a tiny fat bike wheel though a small pit bike knobbly tyre also fits called a 12 - 2.50/2.75.
Relevance of this, none whatsoever, it was either muck about with that or stare at a spiders web for an hour................