Hi thanks guys for all that. So the bottom line is, as my wife has proven, I'm a fussy prick!!! But only in the shed.

It just seemed strange to see the gap. I will chuck one up in the lathe and see if I can re-invent the wheel, just so I sleep better.

Thanks for taking the trouble to measure yours for me men.

Yeh Nikrum I love the fat tires. These steel rims and turf tires came off a ride on mower and as Paul stated, they are heavy, but it's for a "recycle regatta" my fire brigade is hosting in Esperance.
I did get 2 extra fallshaw wheels for when I convert it back to a single seat. I've made the axles ready.
I have the Sismic (from Briskites) 8"x8" alloy rims with 21"x12wide tires on the rear of my kite buggy and a 4"x 8'' with the same tire on the front. This tire/rim set up runs so true and smooth. I use 1 psi in the rear and 2 psi in the front. This set up has lived on Pink Lake and our local beaches for over 12 months and they still look brand new!! I rinse them after every run with the hose when I get home.
They have done 2,732 GPS clocked kms and the bearings still feel fantastic.
Bloody pricey to purchase, but they are quality and were freight free.
Many thanks for your time fellas. Chook