I have re-spoked about 18 wheels in the past but I'm stumped on the disc brake front rim. The bike is a 1972 Commando for which I have purchased a new 06-1951 rim made by Central Wheel but it is not drilled like the original Norton rim. The distributor tells me that Norton changed their spoking pattern sometime after 1974, perhaps when they changed the disc to the left side. But they did not change the part number of the rim. The rim I bought is clearly etched with this part number. I can only assume that Central Wheel copied the newer version which makes it difficult to determine the correct lacing pattern without having the later version old wheel to copy.
The original Norton used what I think is a 1-1 drilling pattern and all the outside spokes radiated in a ccw direction. The dimples simply alternated from one side to the other, and the drillings provided that the dimples on the left side of rim were drilled to accept the spokes from the opposite side of the rim and vise versa.
The later Nortons had all the outside spokes radiating in a cw direction from what I can see from photos, but both versions are a cross 3 pattern that appears identical. The new Central Wheel rim is called a 3-1 pattern I believe. The dimples are in groups of 3 and are drilled with holes on one side (every other dimple) equidistance from the edge of the rim, while the alternating dimples move back and forth across the rim and are drilled to accept spokes from the other side of the rim but at different distances from the edge. So the rim is "handed" but no information is supplied to indicate which is the disc side and which is the off side. The following photos show the new rim along side the old rim which are clearly different. If I can determine which side is the disc side, I can finish up this wheel this weekend. Can anybody help out here? Tom
Someone just recently mentioned that his new rim from the same source couldn't be spoked up correctly, but a new stock rim from another souce was perfect. We think you have just added to that tally....
Could that rim you have be laced to the back hub ? Or the old drum brake front wheel.
A genuine rim here is marked Dunlop MC275.
P.S. The disk brake front rim has one side of the spokes standing almost vertically. If the spoke holes/dimples aren't done according, you have a snowballs chance of getting it to fit.
The bike is a 1972 Commando for which I have purchased a new 06-1951 rim made by Central Wheel but it is not drilled like the original Norton rim.
It wouldn't be the first time I've heard that!
Originally Posted By: koncretekid
The distributor tells me that Norton changed their spoking pattern sometime after 1974, perhaps when they changed the disc to the left side.But they did not change the part number of the rim.
Correct. But reversing the hub and rim assembly simply shifts the offset to the other side and swapping over each pair of inners and outers doesn't drastically alter the positions of the dimple holes so basically the 06-1951 front disc rim should be suitable for all disc front wheels (see Andover Norton link below), although the Dunlop rim number eventually changed to MC288 for MkIII, the early 850 MkIIIs apparently also had an MC275 front rim with the left hand side disc brake.
The new Central Wheel rim is called a 3-1 pattern I believe. The dimples are in groups of 3 and are drilled with holes on one side (every other dimple) equidistance from the edge of the rim, while the alternating dimples move back and forth across the rim and are drilled to accept spokes from the other side of the rim but at different distances from the edge. So the rim is "handed" but no information is supplied to indicate which is the disc side and which is the off side.
This is another CWC oddity, as only the 850 MkIII (MC289) rear rim had the 3x1 dimple pattern originally (the 3 in line on the left side) but the 06-1951 MC275 and MC288 (below) disc front rims didn't.
Disc brake wheel spokes. 1972 Commando with disc brake. Worldwide (Trade only) The spoking arrangement of the disc brake type of front wheel requires periodic attention to correct possible loss of spoke tension. To eliminate the need for regular attention, the following technique which is now applied to all disc brake wheels at the factory should be undertaken at the earliest opportunity (prior to delivery where possible): 1) With all spokes lightly tensioned, tighten left hand side inboard spokes. 2) Tighten left hand side outboard spokes. 3) As shown in the illustration below, set the left hand side inboard spokes straight (shaded heavily) by tapping the bowed portion of the spokes with a 1/2 lb. (.225Kg) hammer and drift 3" (76.2mm) from the centre of the spoke head.
KK Tom This is how I document rim hub and spoke useage. Not showing is the offset from a reference plane to the CENTER of the rim...That way you can correctly offset the rim even if substituting a wider rim. You will note spokes 2&4 are at a very small angle and therefore are the disc side. I normally put in 4 sequential spoke and nipples and press them with my fingers to get a general idea of the angles that the rim was intended for.
I did a spoke test once with a very expensive Devon "show" quality rim intended for a norton front disc and it was so far off is was not even funny. The mate for a MKIII commando was OK, but the pair went back to the vendor ...near to you in NS.
Last edited by Dave Comeau; 11/15/146:35 pm.
dynodave BSA 3 1961-1963 Ducati 3 1992-2002 Norton many 1951-1975 87 Serv-Equip 100HP MC brake dynamometer,
The 3x1 makes a stronger wheel and is much easier to true and get the required rim offset. The 3 dimples go on the non-disc side.
The outside disc side spoke goes to the middle hole of the 3 holes on the non-disc side. This is also the same pattern used on Triumph rear disc wheels.
Thanks to everyone on the forum for your quick replies which enabled me to complete the spoking of the front rim from Central Wheel (3x1 dimple pattern) onto the Commando front hub. I did, however, vary my procedure slightly as can be seen in the following photos. With the disc side facing me and the single dimple on this side, I installed the outside spoke radiating in a cw direction into the single dimple rather than into the middle dimple on the off side. It appeared that had I done that, it would have interfered with the inside spokes. The following photo shows the spokes all threaded thru the hub and ready to add the nipples. I use garden type twist ties to organize the spokes to ensure the pattern is correct before I start lacing. The procedure I used was to thread all the nipples on until the threads on the spokes disappear. Then I tightened the disc side only with a screwdriver until the blade of the screwdriver disengages, i.e. the end of the spoke pushes the bade out of the nipple. At this point I set my wheel in my truing jig, which is just an old Honda swing arm, and I use c-clamps and flat pieces of steel or aluminum as indicators. I then snugged up the off side nipples by hand and checked alignment. The method I used was to pull the rim 1/4" beyond the 1/2" target offset from the hub making sure that the run-out remained true. I could then return to the off side and gradually pull the rim back. After I got it trued in, I started checking torque which of course throws it back out of true. Working back and forth, I got the disc side torque up to 55 in-lbs, then 60, and the offside to about 25 in-lbs. You can't tighten the offside any more than that without over tightening the disc side which will pull the nipples clear thru the rim, which I found out the hard way last week! The final result was true within+/- .003" and runout within .030" (the weld joint on the rim doesn't allow any better for me.)
Again, thanks for the info.
Tom Here is another photo to show the relationship of the outside disc side spoke installed into the single dimple, with it's partner, the inside spoke installed into the middle dimple of the offside three. I don't think the drilling pattern on this rim would have allowed the opposite. Perhaps there are other versions of the 3x1 pattern which would.
Finished wheel makes a nice living room decoration!