Norton wheel sizes in the 1930s

Can anybody out there quote chapter and verse on Norton wheel sizes in the late 1920s and through the 1930s?

From the early 1920s it looks as if Norton quoted tyre sizes rather than rim sizes. Moreover, ithese were in metric dimensions, e.g. 650 x 65 and 700 x 80. Starting in 1924, they drifted towards imperial sizes, and by 1928 were offering 26" tyres as standard. These were initially x 2.50" and later x 3.00" and x 3.25".

In 1932, the first Model 30s and 40s appeared and for these, 27" tyres were on offer; x 3" for the front and x 3.25" for the rear. Into the mid-1930s, 26" x 3.50" and 27" x 4.00" heavy duty tyres were out there as optional extras. All these measurements are presumably outside diameters of the tyres but the critical question is this. What rim sizes corresponded to these tyres? The maths for a 26" x 3.25" tyre, possibly the most commonly fitted size of the period, suggests a 19.5" rim. Very unlikely.

Any assistance with answering this would be useful.