Large Wheelchair Wheel Grey Rubber 610mm - All Questions

Hi, I am looking for possible replacement wheels Esteem V-go. The existing are pnumatic which even when correctly inflated 'squidge' and make it hard pushing up hills in Tuscany hill towns for instance and can't help feeling it would be slightly easier with solid tyres. Providing they are the correct size for replacements...need to measure fully when we return home...are they suitable for out door use...pavement, gravel, cobbles etc ?
Regards