This example shows a tyre width of 3.5 mm for Gauge 0 Fine.
For Scale7 remove more metal from the back of the wheel to give a tyre thickness of 3.2 mm instead of 3.5 mm.
6′ 6″ diam., 22 oval spokes, rectangular rim, apparent tread 4″.
Hub 19″ face dia., 3″ out from the tyre, pin between at 14″.
Casting: 36.2 mm tread dia., i/d 41.9 mm, hub 1.75 mm out from the tyre, pin at 8.17 mm.
Casting prices and stock . GWR loco sets, price list
Scan of a casting in a set for GWR 4-6-0 King
27 Mar 2013