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.
3′ 6″ diam., 10 oval spokes, rectangular inner rim, apparent tread 4″.
Hub 14″ face dia., ½″ out from the tyre.
Casting: 24.5 mm tread dia., 19.8 i/d, hub 0.3 mm out from the tyre.
Casting prices and stock . MR loco sets, price list
Scan of a casting in a set for a MR 4-4-0 Compound
27 Mar 2013