@PMC
Hum,
i managed to fit both tyres inside the (standard sized) rims, but you got to watch that it doesn't pop out when blowing it up....
If you first fit the tyres together - then fit the two `beads` (from one side) of both tyres into the rim - then prise the other two in , it fits quite snugly...
But you got to hurry - the snows melting...