Rear Wheel '72 Commando

pete.v · Apr 22, 2014

pete.v said:
Ok, I just spoke with Buchannan. I do not know if they are the ultimate autority, but I am incline to respect their opinion. Although this may add to the confusion, he said,

"Laying a straight edge across the cushdrive hub, because it offers a consistant reference, it should measure 1 9/16" to the centerling of the rim. This dimension will align the wheel to the centerline of the bike."

It is another way of looking at it than Old Britts and it works for them and is their standard for the 72 Norton type rear wheel.

How this aquaints to offset being left or right I not sure without looking at it. When i get home from work, I sure will check to see where my wheel sits.

I know that my index knuckle with fit between the right swing arm and the tire and the end of my index finger will just fit in the left, I think that is somewhere between 1/8 and 3/16 difference. My axle sits even in the slots and rides very true. I may be right or i may be wrong, but is sure feels right and I would be reluctant to change it just to be right.

Well, by Buchanan's formula I need to bring my hub .042 to the right. I am calling it good for now.

Mcdammit, this procedure will give you at least 1 known figure. FYI, the straight edge goes across the machined surface that is close to the spoke holes on the hub which is about 8" in diameter is , not the rise near the bearing.

madass140 · Apr 22, 2014

Using Buchanan's formula shows the rim is offset to the hub , to the right by .165"

pete.v · Apr 22, 2014

madass140 said:
Using Buchanan's formula shows the rim is offset to the hub , to the right by .165"

The verbiage in the regards to offset disturbs me.

What I here you say is rim offset to the right of the hub rather then the hub offset to the right of the rim, Correct?

I vaguely recall something about this a couple years age where the Old Britts info was wrong.

It seems I must have gotten it right somewhere down the line or gotten lucky with a 50/50 chance. I think I am still happy with the .042 shy of the full offset.

madass140 · Apr 22, 2014

"What I here you say is rim offset to the right of the hub rather then the hub offset to the right of the rim, Correct?"
correct.
not sure if we have solved the problem of the OP though
I think I did a check last week to confirm that the hub is evenly spaced in the swingarm.
I was doing this to confirm what the rim offset would be with my new cush drive hub which appears to have an offset of .100"
as opposed to the standard .165" or .180" as is normally suggested.

Al-otment · Apr 23, 2014

So where does the 3/16" or whatever originate from? And does this apply to all Commando's, what about the different swing-arms and the Mk3 disc hub? The fact there are so many different offset dimensions and datum's flying around implies there is no definitive dimension on the production bikes - production drawings yes, but not the bikes. Say what you like but your just guessing. The time spent discussing and carrying out inconclusive and unsatisfactory checks/adjustments using straight edges, string, plumb-lines etc would have been better spent utilising known two dimensional horizontal and vertical datums. i.e surface table and tool makers blocks. If you haven't got one find someone who has. Do forum members carry out there own cylinder re-bores with a pillar drill?

Hobot · Apr 23, 2014

Unequipped simpleton w/o mentioning names, on my special just made sure stuff along axle allowed chain sprockets to line up and rotor to fit in caliper then with wheel on swing arm on cradle in frame, laced rim to center on steering stem. I hung frame vertical with carpenter level off rafters so gravity did the aligning, I just filled in the blanks. Could send off for accurate measure to record but mine ain't Norton related back there no more but still take my factory Combat just as she came, ie: a bit off in the rear view. Al, the accepted reason all Cdo have at least 3/16" L offset was to gain 4.25-110 size tire chain clearance w/o sticking the poor main shaft's neck out any further. If ya look at the front isolastic mount close ya'll see its assymetric longer on the R. R swing arm leg angles out more the DS before it straightens back to square axle plates.

madass140 · Apr 23, 2014

I think is fairly well documented that the eng/tran is offset to the left, no guessing about that. If you lace your rear wheel on center then it wont take a lot of technical wizardry to realise that you have bad wheel alignment, this of course assumes you have a straight frame and correct wheel spacers. I doubt that people like Buchanans etc lace hundreds of rear wheels with the 3/16" offset because someone suggested its a good idea or whatever. I've laced probably 100 rear Norton wheels,
Commando 3/16" offset. Pre Commando on centre.

Al-otment · Apr 23, 2014

madass140 said:
I think is fairly well documented that the eng/tran is offset to the left, no guessing about that. If you lace your rear wheel on center then it wont take a lot of technical wizardry to realise that you have bad wheel alignment, this of course assumes you have a straight frame and correct wheel spacers. I doubt that people like Buchanans etc lace hundreds of rear wheels with the 3/16" offset because someone suggested its a good idea or whatever. I've laced probably 100 rear Norton wheels,
Commando 3/16" offset. Pre Commando on centre.

Here's how to determine rear wheel offset. Find the centre line on your bike. The frame centre line is described by a line taken from the centre of the steering head axis and passes through the swingarm axis at right angles to it. Once you know where the frame centre line is you then build/adjust the rear wheel so the wheel centre line is aligned to the frame centre line. The offset is whatever it needs to be for the bike your working on, one size does not fit all.

Al-otment · Apr 23, 2014

hobot said:
Unequipped simpleton w/o mentioning names, on my special just made sure stuff along axle allowed chain sprockets to line up and rotor to fit in caliper then with wheel on swing arm on cradle in frame, laced rim to center on steering stem. I hung frame vertical with carpenter level off rafters so gravity did the aligning, I just filled in the blanks. Could send off for accurate measure to record but mine ain't Norton related back there no more but still take my factory Combat just as she came, ie: a bit off in the rear view. Al, the accepted reason all Cdo have at least 3/16" L offset was to gain 4.25-110 size tire chain clearance w/o sticking the poor main shaft's neck out any further. If ya look at the front isolastic mount close ya'll see its assymetric longer on the R. R swing arm leg angles out more the DS before it straightens back to square axle plates.

Hobot,

I agree lacing the rim to suit the frame centre line is the way to go, but ideally you have to consider the horizontal as well as the vertical plane to get everything as it should be. It's been pointed out before that some frames/assemblies would have been better than others just by the law of averages, therefore the variables mean that a single dimension cant be taken as the definitive.

madass140 · Apr 23, 2014

I agree with what you say Al but the average Commando owner would just accept that the rear rim is supposed to be offset
to the right of the hub by 3/16" so thats what they do as well as the wheel builders, not many who are only respoking their wheels are gonna go to great lengths checking frame straightness etc. Maybe from a ground up rebuild it would be advisable to start checking frame straightness etc.

Hobot · Apr 23, 2014

I knew I couldn't keep all the measures straight when adapting a spoked rear Suzuki Water Buffalo hub with switchable sprocket, cush drive and disc rotor mount into a RGM alloy boxed swing arm to clear 530 x-ring chain and 130 tire. Not sure this spindlely thing is up too it so shopping for 16"x5" solid cast type wheel.

Al-otment · Apr 24, 2014

madass140 said:
..... Maybe from a ground up rebuild it would be advisable to start checking frame straightness etc.

I agree 100% with that.

mcdammitt · Apr 29, 2014

OK Hobot,madass140,
What are DS,WSC,LOL & OP?
Checking off set and alignment today
Thanks

Hobot · Apr 29, 2014

,What are DS,WSC,LOL & OP?

DS = Drive Side
WSC = Worlds Straightest Commando, via late Ken Augustine on Phantom Oiler site.
LOL = Laughing out Loud.
OP =???

madass140 · Apr 29, 2014

opening post or poster

pete.v · Apr 29, 2014

Mcdammits pictures.

By looking at your shocks, I would say your swing arm is sprung to the left. It seem the left shock is splayed out at the bottom compared to the right. Appears to be enough to misalign the sprockets as mentioned. Looking at my own and putting a bubble level along the springs, both shocks will cant out a few degrees equally. Your right shock appears to be actually canted in at the bottom ever so slightly.

Try to look at the difference of these next 2 pics, how straight the right shock is compared to the canted left. Also the angle of the left arm of the swing arm compared to the right as it goes to the bushes. Looking on how you may have tried to centerline the tires might also suggest that the axel in not spaced equally in the slots being closed up on the left and a good gap forward on the right.

phillyskip · Apr 29, 2014

If you have all of the "correct" parts the sprocket will line up automatically. I'd look at the wheel "offset" . Your bike needs the correct offset to center the wheel to the frame center line. That's where I put mine.

pete.v · Apr 29, 2014

phillyskip said:
If you have all of the "correct" parts the sprocket will line up automatically. I'd look at the wheel "offset" . Your bike needs the correct offset to center the wheel to the frame center line. That's where I put mine.

Yes Phil, this is a common thought and I thought it myself earlier in the thread.

However, offset has nothing to do with how the hub sit in the swing arm and its relationship the cradle or how the sprockets line up which in this case are way off. Unless the cradle itself is mismounted or the gearbox is off from spacers being left out (although a missed spacers would make it look better than it does) then it tends to norrow the diagnosis to the swing arm.

Snorton74 · Apr 29, 2014

I'm thinking bent swing arm and incorrect offset.

pete.v · Apr 29, 2014

Snorton74 said:
I'm thinking bent swing arm and incorrect offset.

Yes, the offset may also be off, but maybe not . The main issue is the misaligned sprockets. After that, then the possible bad offset can be determined, actually can be check anytime but is truly secondary to the misaligned hub.

Anyhow, I have a sneaking suspicion that the offset is OK.

Rear Wheel '72 Commando

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