Here is an extract from the WM20 standards book (1954) which give the offset measurements for both wheels. I am currently involved in the process of getting WM20 wheels rebuilt for two bikes and have been scrutinising these offsets. Also Previously did some serous checking with the front wheel/forks on my own WM20.

As far as I'm concerned, the measurements given for the front wheel with the left side speedo gearbox are correct.
But I can make no sense of the rear wheel measurements as stated in the standards book Has anyone got a rear wheel out to do some comparisons please.

Ron

email (option): ronpier@talk21.com

Hi Ron.
I have checked my WM20 1941 wheels which are completly stripped of bearings etc ready for rebuilding. I put a straight edge across the hub and took the reading to the edge of the rim and my readings are 1/4" on brake drum side and 3/4" the other .
Jeff

email (option): m90disco@fsmail.net

Hi Ron...I have measured a wheel and have the same figures for the two sides...The (WM3) rim itself, measured over the outside edges, was 3.032" wide....Ian

email (option): ian@wright52.plus.com

Ron Pier

As far as I'm concerned, the measurements given for the front wheel with the left side speedo gearbox are correct.
But I can make no sense of the rear wheel measurements as stated in the standards book

Ron

Hi Ron

What the original data fails to clarify is that the rear measurements are made from the outer faces of the installed "hollow axle" (bearing sleeve) and its corresponding outer nut to the rim edges. The "hollow referred to in text is not the hollow of the actual brake drum which must be removed to do the check.

Bear in mind the accuracy of this "factory" check can be affected by spacer width for outer races and "fiddled" bearing sleeves and nuts.
I have also found variations of several mm in WM3 rim widths.

A more practical dimension for restorers/wheelbuilders is from the bolting face for brake drum to centre of rim, which is around 44mm

Its easy to get carried away, in my experience, if both wheels are vertical in frame and rear wheel is not skewed in axle slots, it is almost impossible to notice up to 5mm misalignment due to offsets, or slightly tweaked frames.

Neale

email (option): n.gentner@bigpond.com

Thanks chaps for measuring your wheels. The 1/4" stated more or less agrees with my findings. Thanks Neale for clarifying the text, and the extra measurement to wheel centre. That gives me something else to compare. And yes I have also found variations in WM3 widths.

Cheers all. Ron

email (option): ronpier@talk21.com

Hi Ron
From measuring my old wheel and confirmed by studying various drawings, measuring parts etc, I get the following offsets: 4mm on left (brake) side, 22mm on right side.
Hub width = 102mm, Rim width = 76mm.
Regards
Peter

email (option): pvlietstra@gmail.com

Thanks Peter for giving me another one for comparison. Just got to fire up the calculator to put those Napoleonic measurements into our silly English ones Ron

email (option): ronpier@talk21.com