Hi Dave.
This picture may help,
IMG_1536.jpg


The procedures as follows:-
1/ cut disc with 3" cutter.
2/ drill out to 8mm, then tap 3/8" unf
3/ cut bike tyre long enough to go round disc, then cut down the middle.
(the tyre in the picture will do 2 discs)
4/Cut a buttress profile along one edge, (I used the side that was closest to the rim)
5/With 3.5mm*15mm wood screws fix on the tyre, I used a 2mm pilot drill for this bit.

Hope this helps, but I don't know if the wheels will work yet!