Wheel Alignment

Much has been written about the rear wheel not being in line with the front on this forum and on access norton forum. An that it seems to have been made that way by the factory for reasons of drive chain alignment. If that is what you mean by 8mm run out (i'd say offset) it sounds similar to other reported figures. If you mean the wheel rim itself has 8mm of run out this is an issue that should be dealt with as 1/2mm is the normal tolerance.

Hi Gordon

Try contacting Simon Ratcliffe on the "parallel engineering" website.

Previously gordon_robertson wrote:

offset is what I mean.

Wondered if I should offset therear wheel rim by spoke adjustment to bring both wheels into alignment?

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Yes!

Wondered if I should offset therear wheel rim by spoke adjustment to bring both wheels into alignment? Yes x 2. Headtube at 90 degrees to ISO mounts. Front wheel centred in forks and rear wheel offset 3/16" to right in swingarm or as needed to align with front. This is for bikes with symmetrical swingarms, ie up to mk2 850. I am told Mk3 are different and have offset swingarm pads to compensate for cradle and front mount offset so wheel is basically centred in arm. I have no experience of these.

this might help in some way . Baz http://www.nortonclub.com/docs/Straightest_Commando_Frame.pdf

Hello Gordon not a commando owner myself. just trying to help .sorry if its caused you any distress. Baz

Hello Gordon. i read most of it my self just saw the bit about the rear wheel sits more to the right in the swing arm thought that might be misleading your measurements in some way . i don't think anything would stop me buying a commando. at least there are people out there that can put it right if anything major is at fault thats the main thing . Baz

Previously gordon_robertson wrote:

Previously K Glassborow wrote:

Wondered if I should offset therear wheel rim by spoke adjustment to bring both wheels into alignment? Yes x 2. Headtube at 90 degrees to ISO mounts. Front wheel centred in forks and rear wheel offset 3/16" to right in swingarm or as needed to align with front. This is for bikes with symmetrical swingarms, ie up to mk2 850. I am told Mk3 are different and have offset swingarm pads to compensate for cradle and front mount offset so wheel is basically centred in arm. I have no experience of these.

Hi,

Just measured the rim offset.

From the cush drive hub torim, the rear is offset 5mm(3/16") to the right.

From brake disc mounting flange to rim the front wheel is offset 13mm(1/2") to the right.

Thave a good night.he rear wheel would have to be offset to the left to align both wheels, is this normal?

Rear offset sounds about right. On the front just measure rim to slider (stanchion more accurate though). Side to side should be the same. The rear offset to the right then counters the cradle and swingarm offset to left. Remove your head steady and you can measure offset there. It will be 1/8 to 3/16". The front mount and cradle will be similar but can vary depending on how accurately they were originally jigged. Having different offsets between the front mount and cradle can pull the whole drive assy around in the frame and make for odd handling. Even if these are the same, frame straightness and ISO tab mounts must be on the money. This is where that article makes sense. Just concentrate on getting both wheels in line.

The strange thing is the rear wheels needs to be offset to the left to be inline with the front wheel.

Yes, that is not the way it usually is. Since the cradle and swingarm is always offset to the left on all models something is not right. It defeats the logic of moving the wheel to the right to give chain-tyre clearance and wheel alignment. It is odd and the ISO end caps cannot be so worn that the whole assy has moved on the rubbers. They'd have to be paper thin at one end for that to happen and you would notice handling issues!!

How are you measuring alignment? With straight edges, string? I'm not saying you are doing it incorrectly, just wondered. I've never been confident of accuracy that way although a couple of straight edges clamped to the rear wheel will show if the front is not in line.

I suspect one of the problems is that due to the unusual construction, Commandos were never jigged complete with swing-arm during production which I would have thought was normal for most motorcycles.

Presumably they jigged the frame but only steering axis to rear isolastic cross-mount - there are no other datum points. Were swing-arms then jigged after mounting to iso cradles ? I doubt that too.

If you then combine this with the difficulty on the disc brake models of getting the rim pulled over far enough to the disc side, there are plenty of areas for error to creep in...but as Keith says, this failure of the rear wheel to sit centrally in the frame, visible on most bikes by looking at the rear frame loop suggests a fundamental mis-calculation or perhaps more likely a production change that had consequences which were not fully taken into account.

Did they set the rear wheel to the left as they couldn't get the front wheel pulled over far enough to the right to centralise on the right hand disc models ?

The Commandos basic ability to sort itself out under most circumstances (probably due to the rubber hinge in the middle) means that for most riders, most of the time, it ws OK.

I would want to check front wheel centralisation with sliders removed before changing anything. There is no guarantee that brake and pinchbolt side sliders have the same wall thickness. There won't be a 5/16" difference but it all adds up.

Previously gordon_robertson wrote:

Previously richard_payne wrote:

I suspect one of the problems is that due to the unusual construction, Commandos were never jigged complete with swing-arm during production which I would have thought was normal for most motorcycles.

Presumably they jigged the frame but only steering axis to rear isolastic cross-mount - there are no other datum points. Were swing-arms then jigged after mounting to iso cradles ? I doubt that too.

If you then combine this with the difficulty on the disc brake models of getting the rim pulled over far enough to the disc side, there are plenty of areas for error to creep in...but as Keith says, this failure of the rear wheel to sit centrally in the frame, visible on most bikes by looking at the rear frame loop suggests a fundamental mis-calculation or perhaps more likely a production change that had consequences which were not fully taken into account.

Did they set the rear wheel to the left as they couldn't get the front wheel pulled over far enough to the right to centralise on the right hand disc models ?

The Commandos basic ability to sort itself out under most circumstances (probably due to the rubber hinge in the middle) means that for most riders, most of the time, it ws OK.

I would want to check front wheel centralisation with sliders removed before changing anything. There is no guarantee that brake and pinchbolt side sliders have the same wall thickness. There won't be a 5/16" difference but it all adds up.

After you have checked everything you can, just follow the Commando manual instructions on wheel alignment. Use one rear spindle adjuster to turn the rear wheel into line. The front wheel will turn in to suit. As long as the drive chain isn't stressed the bike will run better and not eat tyres.

To line my Commando wheels lined up I stretch insulating tape from the front rim to the rear rim, which I find gives an easier to see eye line than string or a straight edge. I then get the wheels in line even though the adjuster screws may be not equal. So long as the chain run off the rear sprocket is ok I am happy with that.

With a Dave Taylor head steady and Avon Road rider tyres my Commando handles well enough to scrape the exhaust on bends, get me to all the places I want to go, tyre life is ok, and it seems as least good as any other 70s or 80s bike that Iv owned.

After offering 'advice' to Gordon R I revisited my bike's alignment, especially after his comment on the rear wheel needing to be pulled left to align with front. I now realise I know little about the subject.

Years ago I tore down the bike to crankcase level and with front mount and cradle machining (tube ends) and shimming I got it to slide into place without pulling the cradle around. That solved the 80mph weave and headshake. I then plumbed the forks and swingarm centres and adjusted front wheel to central and rear offset to a little over 1/8"right of centre. I even filed the axle holes top and bottom so they were parallel with the shaft. It all seemed to make a difference and generally nicer to ride. Well after just running string lines from the rear wheel to the front at 6.5" height I had 0" on left but over 1" clearance on the right with the bike vertical (4 ft spirit level against tyre) and front axle centres equidistant to front mount thru bolt and that's without the left line touching the front of the rear tyre. As to what I meant by knowing little I couldn't understand the huge offset....eventually realising that pulling the rear around on the adjusters (1.5 turns each way) would improve things and now have a nominal 3/16" on left and 5/16" on right. So the rear wheel still needs adjusting to move it 1/8" further left. The tyre (110) should clear the chainguard.

So, I've been riding around for 6 or 7 years with the rear wheel pointing right and still somewhat offset to the right despite messing about with plum bobs etc. I couldn't even get the offset right and I completely missed the major exercise....ALIGNMENT !!! and at some time decided that equal stickout on each adjuster was fine. It's likely this is Gordon's only problem, a wheel misaligned in the axle holes and bearing in mind its only 8mm out, a turn each way on the adjusters should fix it. String lines will confirm. Dave Taylor's advice could not be better and it'll be interesting to see how mine handles when I've re-done the offset, that's if it's correct this time round