Pics of Wheelchair Tyre - Fitting Attempt

Hi :)

In trying to fit these tyres, I think I got something wrong with the sizes. Wheel and tyre both say 24 inches. The old (worn, stretched) tyre looks like it will go on, new tyre looks comletely nope...

Heating the new tyre makes little difference, I don't think the string expands at all and that's what's stopping it.