70 Rear Wheel 3/8" to the left

I've been working on a 72 Commando Roadster for a couple of months now and this site has been a wealth of information that I've taken advantage of, with thanks to all.

As a preamble, I bought the bike because a) I had a love-hate relationship with a '69 Fastback back in '73, b) the engine ran and sounded alright, c) the chrome was very good, and d) the PO accepted my offer. At the time the obvious problems were a rattling exhaust pipe at the right head, neither center nor side stand fitted, bodged wiring, and side covers loose. On the plus or at least not negative side, a Boyer ignition and a single Amal conversion were fitted and it came with a NOS Fastback tailpiece as well as the stock Roadster one.

Herb Becker replaced the thread insert on the right, and the left one was salvageable. The problems started with the PO fitting shorter 850 nuts and solving the clearance by putting three exhaust gaskets on the left and none on the right. I think JB Weld or mystery goop was his solution (picture below) on the right nut as the threads tore out with the nut. Brass 750 nuts from Walridge have taken their place. The head was off twice as the #9 head stud wouldn't take torque. Fortunately it was the stud, not the thread in the barrel.

A CVMG jumble yielded a center stand (no stop plates fitted), further bodging got the side stand on, though clearing the exhaust has the spring hanging on the pivot bolt head, and Fastenal Canada had the shaft collars for the (Kegler?) swing arm pivot pin (loose in cradle) fix so I did that.

The right side cover has the flange for the lower grommet missing. Turns out the oil tank was sticking out too far at the bottom. That was caused by finding (I think) the rear fender must be wrong for the oil tank as the return pipe on the rear of the tank fouled the rear fender. A bag of sand and Mr. Hammer have solved that. There's lots more, as there is to every Norton story, but to cut to the chase here's the problem.

The rear wheel sits about 3/8" to the left in the frame. The rear wheel and brake hub are wrong for the year as they do not have the cush drive, using the 3 long nuts to hold the wheel hub to the drum. The spacers seem right against the early parts manual. Sighting down the back tube the frame seems straight, the chain is aligned well on the two sprockets, the wheel is parallel to the frame, the swingarm is centered (tightly) between the exhaust mounting plates and the rim is centered on the hub rather than offset. To further add to the quandary, the frame may even be from a later 850 as a more knowledgeable guy than I thinks the gusset plates under the top rail by the shocks (picture below) were not on the '72s. Unfortunately the first digit of the frame number isn't visible so it could be either a 2 or a 3. The engine and transmission are 2008xx and the frame is ?001xx.

Here are three pictures of the area. I think it's too much to take up with spoke offset and may be solved by finding the correct wheel/brake assembly. Another knowledgeable Norton guy (Keith Newton) says that should be done anyway to save the transmission gears.

Any guidance on the wheel alignment issue will be appreciated. Here are the photos, in diminishing order of relevance.

Wheel mounting, left side




Wheel mounting right side




Drum to hub detail




Rear frame detail (right shock mount gusset)




Single carb conversion (thought it was a Mikuni until I cleaned it)




Odd hard goop on gasket surfaces. It chips cleanly off the aluminum, leaving the casting unmarred.




A poor shot of my old love back in the day




Thanks much,

Brock

Welcome to the forum, Brock.

captainkcorb said:

To further add to the quandary, the frame may even be from a later 850 as a more knowledgeable guy than I thinks the gusset plates under the top rail by the shocks (picture below) were not on the '72s. Unfortunately the first digit of the frame number isn't visible so it could be either a 2 or a 3. The engine and transmission are 2008xx and the frame is ?001xx.

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The knowledgeable guy is right, 850 frames from late '73-on (850 Mk2 & 2A) had extended inner shock gusset plates-so the first serial number could be '3', however, a serial number as low as 3001xx should be from early '73 850 Mk1 production?

Is the frame number stamped on the certification plate riveted to the headstock, or is it stamped directly onto the frame? If it is stamped on the frame then the illegible number may perhaps be 'F1' (F1001xx).

http://atlanticgreen.com/commandoframes.htm

Check if there is a 6-digit number stamped on the front face of the left hand fuel tank bracket? If it's an 850 frame, you should find the frame part number, either 064140 (850 Mk1) or 065404 (Mk2 & 2A)

Looks to me like you've got all the correct spacers. Wonder if there is anything different about the 850 swing arm? But 3/8 may be able to be corrected by adjusting spokes. It really doesn't take much to move the rim over 1mm. As I remember the hub on mine was pretty much centered to the rim but when I re-spoked it, I took measurements and reproduced what I had. How do you know it's 3/8 off? Are you measuring from the center of the main tube? If you take the shocks off, you can push the rim/wheel up above the rear loop and put a straight edge on the rims and compare one side to the other against the main tube.

Dave
69S

A handfull of 750's i've looked close at all had some LH shift of tire centering in frame loop/fender of ~3/8". You are stuck with keeping the chain drive sprockets in line, which occurs naturally with factory axle/spacers, drum/hub assembly. The off set tire-rim is purely cosmic issue unless a type of stunt ride that can sense a bit more ease to fling to RH than left about as fast as ya can. Some might be gained with spoke tweaking to look better to those following or snooping at rallys.

Spindle collars may not help long term if spindle bushes and surrounds are already worn out. Having done 2 Cdo peicemeal from the outside I now think it way more time-money long term peace of mind efficient to take it down to crank and work back up. Beware hidden disc brake leaks by checking in for a few 100 to 1000 miles to avoid a last surprise.

I think 1/4" to 3/8" to the left sitting in the swing arm is about right. The keys are the sprockets are in line, swing arm is square, adjusters are equally on the notches and front and rear wheels in line. All this with a "no hand" ride straight and true.

After lacing up some new rims last winter, I did much research on offsets and on exactly where everything sits.
I believe your numbers are good.

Thanks for verifying my conclusion, generally the rear is LH offset a bit, after many telling me no they ain't. When good tires fitted my Cdo's don't drift L much nor wiggle bar coasting below 50 hands off. But that don't last a couple 1000 miles here. When I did Peel's new alloy rear wheel I laced it to center in loop and gained chain clearance to fit 130 tire.

Here are some posts on offset. Pay particular attention to Vern's.

http://www.nortonownersclub.org/support ... el-offsets

I do know that the 750s had a symmetrical arm and the rim offset 3/16" to make up for it.
Vernon Fueston (fueston@snowcrest.net) on NOC-L 11th. Nov 1997

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Vern's geometry lingo confuses me about Commando offsets. What I see is longer iso tubes on RH to shift power unit to LH and swing arm followed it over with cradle. My down &dirty rear wheel aligning method, to just feel for equal space on each side of tire and swing arms is in question, though sure seemed to align chain ok. I know RH arm is angled outward to compensate for the L shift of power unit but that does not affect the relationship of tire centering at front of swing arm. So could those that know their two tires are inline and parallel, could ya check the tire-arm relative R/L spacing and report what ya found?

A long searching will reveal a number of past and famous cycles with tires not inline once set parallel and nothing wrong with assembly. I can just barely tell a Cdo bias to fling R a tad easier/faster than L but don't know if that tire offset or Center of Gravity, which I think is offset to L even more than the power unit d/t the primary and final drive on that side. This LH CoG could also account for some of the LH drift tendency and thus also confuses my sense of why the RH bias. I'm definitely more comfy tossing down on L than on R. So don't think my sense of bias is a personal one. I am L handed intermittent dyslexic if that matters. I've read reports many pilots like LH flings better and some theorize its because our dense hearts are L of center. It took some work to get over my hesitation to push hard over R but did as that's the best leaning side when stands installed.

hobot said:

Thanks for verifying my conclusion, generally the rear is LH offset a bit, after many telling me no they ain't. When good tires fitted my Cdo's don't drift L much nor wiggle bar coasting below 50 hands off. But that don't last a couple 1000 miles here. When I did Peel's new alloy rear wheel I laced it to center in loop and gained chain clearance to fit 130 tire.

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I think the only thing I have verified is that although my bike seems to handle really good the way i have it, it doesn't mean I have it correctly set up.

After reading many statements, the only conclusion I have come up with is that they are contradictory and uncertain. It is too easy to confuse things like "offset to the right", "measure from the flange and not the backing plate" and "view it from the edge to the spoke flange measuring from the center of the rim looking down from the edge".

One thing i feel "IS" correct is that front rim should be centered in the forks.

The one thing that I am "NOT" sure of and what seems to be most elusive is if the rear rim should be in the middle of the swing arm, assuming that all things are straight and true.

So, cradle 1/8" to the right, swing arm 1/8"to left, hub offset to the 3/16" to the left to center the wheel on swingarm. This will contradict the Old Brits statement of offsetting the rear drum hub to the right by 3/16" of which will leave the wheel/rim 3/8" offcenter to the left in the swingarm.
Just great! I hope this clears things up. NOT!

pvisseriii said:

So, cradle 1/8" to the right, swing arm 1/8"to left, hub offset to the 3/16" to the left to center the wheel on swingarm.

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The cradle is offset 1/8" - 3/16" to the left of frame centre.

There has been some debate about whether the swinging arm is symmetrical or not (Mk3 arm appears not). As the cradle is offset, then it follows that the swinging arm needs to be offset in the opposite direction by an equal amount otherwise the shocks would lean over to the right, if the swinging arm is symmetrical and the shocks are vertical when viewed from the front or rear then the whole cradle and swinging arm assembly cannot be totally parallel to the frame.

I see no good reason for having the rear rim offset from the frame centre line by as much as 3/8" and personally, it is something I would correct.

I've seen both 750 and 850 swingarms, both have a more inline LH arm and an more angled out RH arm, which gives more acute angle backward of the axle plate on R. The two arm seems to meet centered at the front cross brace, near where Ifinger check tire alignment in shed or side of road flats. No arquement inline tires should be inline but Commando are dang good handlers up to THE Hinge, and so many have the rear LH offset a bit, so mostly a cosmic effect - unless my sense of RH tip bias is correct, its still a non issue its so sublte to detect and rather hard to induce.

Thanks for all the input Gents.

I'm still left with wondering if there is a dimensional difference between the rear wheel assemblies with and without the cush drive system. Not a difference in the swingarms or cradles but in either the drum or wheel hub width. I'll take a measurement from the left swing arm plate to the hub center on this one, and visit a friend with a beer in hand and measure his later hub. If there's a difference I'll report in.

As an action plan I'll enjoy it as is in the short term and ride. Should I get the wheel hub re-laced (when not if) I'll have the rim offset 3/8 to the right to compensate. That much offset must be OK given the extremes that the front has. If it's an artifact of the wheel swap then I'll put more emphasis on finding the later hub.

Hobot's comment on a full teardown being the way to go in the end is right on. Given my spotty history of completing projects in a timely fashion, I swore that I'd get the exhaust nut fixed on this one and get on the road, damn the torpedoes. That hasn't quite worked out and I'll still be looking at a teardown once it's running, if for no other reason than to recoat the frame and deal with the nasty frame tube damage (squeezed) at the side stand mount.

I'll post a shot when the body panels are back on and it looks more complete.

L.A.B. said:

I see no good reason for having the rear rim offset from the frame centre line by as much as 3/8" and personally, it is something I would correct.

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OK! My rear hub is offset 3/16 to the right as stated in the Old Britts tech files. This leaves the rim 3/8" off center to the left. If I shift my hub offset 3/16" to the left, move it a total of 3/8" to the left, this should bring the rim on center. This tells me that Fred needs to re-word his statement or explain what the hell i am not understanding.

Winter is setting in now and i believe i have taken my final last ride of the year. If I didn't have something to feddle with, I would create some to feddle with so I am not really sad about this.

I am, however, concerned about other being mislead and perhap have a safety issue in this regard.

Hi, I assume the rim should be centered in in line with the spine frame, idest the rim must be in equal distance within the rear shocks .........isnt it?

The cushions should not be proud enough to prevent axle nut clamp force to fully seat on all the spaces and inner races of bearings. In general there is about 1/4" gap seen between drum and hub. There is no good reason for off set rim expect expedient factor assembly warranty didn't cover. If gap wider or smaller than this then be pensive something amiss that may raise the probability of radioactive axle to fission as they all will just not a lot at once with say a 40 yr half life. The rear bearings tend to dry out d/t slight shoe drag and actual use, so each tire renewal or flat its good to check in or just re-grease preventatively, if not sealed type which too can over heat and melt out. It sure erked me trying to center my first Commando and made me pensive something was amiss with me or the bike or both. I now know what it takes to relace or recenter old spokes so basically gave up on my factory Trixie with both 18" and 19" rear rims on hand. Rear flats switch outs.

So still waiting to find out if my finger space swipes at front of rear tire is as good as the stick and string or laser alignment methods...

I've spent 37 years struggling to get my wheels lined up without skewing the wheel in the swinging arm. Finally set it up upright (spirit level on the rear iso bolt) on a granite worksurface. set a straight edge down the middle of the rear and front iso mounting plates. fitted a 25mm dia rod through the steering head. The centre of the rod was about 1/4 inch to the left of my centre line. I set up two other frames in the same fashion and they lined up perfectly. The headstock does not bend but the rest of the frame can be pushed across to one side like a parallelogram. The give away for this is when the front iso bolt is way out when trying to get it through the LH frame lug. The wheels are out of line in the vertical plane. There was no obvious damage to the frame.
Managed to get an unused 69 frame from a fellow branch member, how lucky was that? the old one is in the naughty corner!

Given that the chain is running true, I measured the distance between the mid point in the chain rollers across to the wheel hub center. It's 3". It seems that lacing is the only way to center the rear wheel at this point. The front wheel is well centered between the sliders. Thanks for all the info and advice.

Another night in the shed sorting out the last few oddities in the wiring and cleaning odd bits. I'm thinking a few sober hours tomorrow and she'll be ready to kick to life.

Indeed, the dynamics of chain run & dimensionally true track wheel alignment are more important for riding reasons than apparent aesthetic/visual discontinuity, unless show or mentally overpowering need for symmetry [straighten that picture hanging on the wall] are the priorities.