I have just bought a pair of the modern equivalent rear bearings for a WM20 number 30204. They are the same size as the originals apart from the width of the outer race. which is 12mm for the new ones but only 11 mm on the originals. Will this 1mm difference interfear with felt seal dust caps etc? Ron

email (option): ronpier@talk21.com

No serious affect Ron, so long as the inner tin cup doesn't foul the bearing cone
You can also chuck the felts and outer tin cups and replace with a modern seal from any bearing supplier.

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

Hi Neale...Do you have a number for that seal?...or the dimensions?....Ian

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

Hi Ron,

I noticed the same but had the feeling the difference was more than 1 mm, anyway I replaced the washer between the driveside bearing and the shoulder of the bearing sleeve for a thinner one. If you don't the brakeplate will be further from the drum and as it works on both sides you will find the the bearingsleeve is a bit to short for the adjusting nuts and washer. It will also enlarge the whole width of the complete wheel.

But if you do so also check that the 'rear hub spigot and brake drum support - 66-6104' doesn't touch the dust cap of the hub when the wheelspindle is fastened.

Good luck, Michiel

email (option): m.wijbenga@hotmail.com

Seal I use for rear hub is metric 30 x 47 x 7, KOK TC12492.
ID is a little tight, I polish the sharp edge off left side spacer and right side inner nut, grease to ease passage and lubricate seal, if worried about ID you can remove and discard garter spring.

As most of the wheels I see are early non taper bolt type with elongated stud holes, I usually take a different approach for left side seal.
I discard the left side felt and tin cups, machine up a steel ring which sits proud of hub and forms a spigot to centralise brake drum/sprocket to hub.
Brake drum is then installed and checked/adjusted for concentricity with hub/bearings. I then remove one drum/sprocket bolt at a time and countersink worn hole, fit new countersunk bolt, repeat for all 3. This helps prevent rear brake pedal pulsing due to eccentric drum, but downside is the loss of the left side hub seal.
However, I use a 38 x 52 x 7 KOK 12540 seal, mount on a mandrel, machine the OD down to suit and install it in sprocket in lieu of the larger felt, same deal, real seal is a little tight on ID due to imperial dimensions of short axle, but rotation is relatively slow and I don't like to re-machine things unnecessarily, again you can remove garter spring if concerned.
You might be able to source a proper imperial seal, but in OZ the range is very limited and above is as close as I could get.

On final assembly I seal drum/sprocket to hub with Loctite Mastergasket so water can't enter via bolt face and tell owners to treat their rear wheel as non QD.
Keeps the water and dirt out of hub and the grease out of brake drum.

Re 30204 bearings:
Michiel is correct, the assembled height of modern 30204 is greater than the original bearings, so thinner cup spacers should be used.
Another area for wheel offset to go out of whak!

First, do no harm.

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