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′ 3″ diam., 21 oval spokes, gap by the pin filled and reinforced each side, rectangular inner rim, apparent tread 4¼″.
Hub 19″ face dia., 2¼″ out from the tyre, pin between at 15″.
Casting: 43.75 mm tread dia., 38.7 mm i/d., hub 1.3 mm out from the tyre, pin at 8.75 mm.
Casting prices and stock . GWR loco sets, price list
Scan of casting in a set for GWR Hawksworth 4-6-0 County Class
27 Mar 2013