Wheel rim size confusion

I have WM2 replacement rims on my 60  99  for the last 25 years . With  300  x19 Avon ribbed front  and 350 Avon SM rear ,  Anything more modern  is wider and  may not clear on some bikes. .I have come across WM1 rims  and  while may work with  a 275 or 300 front  ,is no use for anything bigger. You need to check the rims are central in forks and rear  suspension units.That usually works well enough, although the wheels may be slightly out of line. Getting them perfectly in line and central is good but can be a bit of a faff. Due to weight distribution perfectly central does not always handle perfectly !. So if it feels good ,it is good.

Just make sure you are checking Bacon's properly. 

The early Model 7's had Wm 1 rims fitted with 3.00 x 21" tyres. These changed to WM2 rims and changed to 19" tyres during1953.

Rim widths from Avon's site.

WM1 1.6

WM2 1.85

This is the width between the flanges is where the tyre sits.

Not sure where you got your info from, but-

WM1 is 1.65 inches wide

WM2 is 1.85 inches wide

WM3 is 2.15 inches wide

I'm sure your bike would have had WM2 originally. WM1 is very narrow and usually only used on smaller bikes with skinny tyres. Relax, you will be fine with WM2.

Ian

The bike handles the best of all the bikes I have ridden.  The SM rear  has very deep sidewalls and runs at a lower pressure than  you would consider right. the sidewalls are designed to flex and allow the tread to stay on the road  ,quite different to the modern round profile tyres ,works well as long as you don't overpressure or try for knee down. When they do let go on slipery greasy roads you can feel it slide and correct it like Rossi !!, absolutely NO highside .I also get to  ride a VTR 1000 Firestorm ,an MT10 and a BMW 1200. I still prefer the 99. I would be happy to use modern rubber but no room on my bike . Interestingly the late Atlas on modern rubber feels like a tank in comparison ,not sure why, work in progress.

John is not incorrect with his mention of a 1.60" inside well width. The WM 1 Rims when made in alloy often lost that 0.05". The Devon Wheel Company used to offer Flangeless WM1 Rims  with 1.65" and Flanged WM1 Rims with 1.60" wells.

The attachments may be of use to Tony Wood as the pages cover a range of points relating to Norton Wheels, Tyres and Rims.

"I can't believe that any other bike could handle as well as the Featherbed, which didn't care what tyres it wore."

I take it that you haven't ridden anything made since around 1985 then (or earlier if Italian)

Featherbeds do indeed handle well and goes around corners pretty well, and considering that the design is 70 years old it is amazing, but any modern (2000 on) 600 would run rings around a Dommi nowadays. Evolution and all that...

I have a 500cc single with a Featherbed frame made in 1955 which runs very well on TT 100s and they look right for the machine.  The rim size is 19 inch WM2 front and rear.  There is just enough clearance between the tyre and the swinging arm.  I could have fitted Avon Roadrider Mk.IIs but whilst they would have [probably] produced even better handling they would not have looked correct on the machine.  I am using the same size as a Commando, 3.60 / 19 front and 4.10 / 19 rear at 28 psi front and 30 psi rear.  I have Avons in the sizes 90/90 front and 100/90 rear on my 1978 Commando and both look slimmer and skinnier than the Dunlops.  Tyres and pressures are always very subjective issues; Phil Read's son, Graham, ran rings around me on his Suzuki GSX1100 but he ran his tyres at 12 psi front and not much more in the rear [usually on race tyres marked Not For Road Use].  He ran the bike on Jersey plates and whenever he was stopped for speeding [which wasn't very often because they couldn't catch him] he always got off by saying that he was flying back to Jersey the next day.  On the other hand, I was riding a 100,000 mile CX500...