3′ 2″ diam., disc wheel, apparent tread 3½″.
Hub 10¾″ face dia., ½″ out from the tyre.

Source works drawing.

Casting: 31.7 mm tread dia., 26.0 i/d., hub 0.4 mm out from the tyre.

Casting prices and stock . MOS/WD loco sets, price list

Scan of a casting in a set for a WD 2-8-0 or 2-10-0