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front wheel offset on disk brake commandos

Classic Norton Commando Motorcycles.

Re: front wheel offset on disk brake commandos

Postby L.A.B. » Mon Mar 06, 2017 12:48 pm

bucksfizz wrote:I'm restoring a bitsa ('74 Mk2 engine and swinging arm in a '75 Mk3 frame), and I was going to start a separate thread entitled: why is my rear wheel offset to the left?

Perhaps the answer is that the front wheel is similarly offset in the front fork.


I would say not, the rear rim being offset too far to the left is a common-enough problem especially if the wheel has been rebuilt and needs correcting in my opinion.
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Re: front wheel offset on disk brake commandos

Postby pantah_good » Mon Mar 06, 2017 1:38 pm

Deets55 wrote:....leveled the bike on the center stand. The leveled a steel rule between the fork tube and then used a square to locate the rim center. But the tire needed to be removed.

I checked with Pete, and this is the photo he was talking about, from when I was building my front wheel. Hope it helps, worked for me. Page 2, "1972 Roadster Rebuild" thread.
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Re: front wheel offset on disk brake commandos

Postby Deets55 » Mon Mar 06, 2017 3:24 pm

bucksfizz wrote:I'm restoring a bitsa ('74 Mk2 engine and swinging arm in a '75 Mk3 frame), and I was going to start a separate thread entitled: why is my rear wheel offset to the left?
Here's what it looks like:

Image

Perhaps the answer is that the front wheel is similarly offset in the front fork.


Somewhere at home I have Buchanan's offsets for a MKIII front and rear wheel. If you want I can look for them tomorrow and post. They were very, very close to my final numbers.
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Re: front wheel offset on disk brake commandos

Postby L.A.B. » Mon Mar 06, 2017 3:32 pm

Deets55 wrote:Somewhere at home I have Buchanan's offsets for a MKIII front and rear wheel. If you want I can look for them tomorrow and post. They were very, very close to my final numbers.


It's only the frame that's Mk3.
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Re: front wheel offset on disk brake commandos

Postby Deets55 » Mon Mar 06, 2017 4:11 pm

L.A.B. wrote:
Deets55 wrote:Somewhere at home I have Buchanan's offsets for a MKIII front and rear wheel. If you want I can look for them tomorrow and post. They were very, very close to my final numbers.


It's only the frame that's Mk3.


I was thinking at least the front wheel might be the same since they were both disc, even thought they are on opposite sides. I have seen where some people have switched theirs around with no mention of changing offset. I'm not familiar with the earlier rear, and I can't recall where the pickup surface on mine was, possibly the disc mount? In which case that number would not be of any use.
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Re: front wheel offset on disk brake commandos

Postby L.A.B. » Mon Mar 06, 2017 5:06 pm

Deets55 wrote:I was thinking at least the front wheel might be the same since they were both disc, even thought they are on opposite sides.


Yes, although as far as I'm concerned, the front rim should just be set on (or as close to) the steering axis as possible regardless of any known offset figure. The amount of rear rim offset may also vary between individual bikes so the offset should be determined by actual measurement in my opinion.

https://www.oldbritts.com/lacing_info.html
http://www.nortonclub.com/docs/Straight ... _Frame.pdf
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Re: front wheel offset on disk brake commandos

Postby Deets55 » Mon Mar 06, 2017 5:33 pm

L.A.B. wrote:
Deets55 wrote:I was thinking at least the front wheel might be the same since they were both disc, even thought they are on opposite sides.


Yes, although as far as I'm concerned, the front rim should just be set on (or as close to) the steering axis as possible regardless of any known offset figure. The amount of rear rim offset may also vary between individual bikes so the offset should be determined by actual measurement in my opinion.

https://www.oldbritts.com/lacing_info.html
http://www.nortonclub.com/docs/Straight ... _Frame.pdf


I agree. I used a laser from the center of the steering stem along the back bone. Then I measured to the outer edge of the hoop to the laser line. Both sides were equal. I then made sure the swingarm and hoop were level and parallel (left to right) to each other. Then dropped a plumb bob over the outside of the hoop on each side so they crossed the center of the axle ( trying to make sure I was square to the center line) and measured to the rim edge to center it. I roughed it in using Buchanans numbers and found it to be very close to my final numbers. I am sure there are a lot of ways to do this, this seemed to work to best for me.
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Re: front wheel offset on disk brake commandos

Postby Mr. Rick » Tue Mar 07, 2017 12:25 am

Thanks again, Pete, for the level/square idea, and thanks also to Bill, for bringing the picture into the thread.
I will pull off the tire and see if my steering axis pointer gives a different reading, which if so, wd indicate poor tire manufacturing. I don't really expect to find a difference.

oOnortonOo: Thanks for your input. I do actually have confidence in the pointer. I can spin the rod and see the tip wobble (precess?) a tiny amount, as it's not perfectly straight. I can rotate the stoppers and note no movement in the pointer position at all. Having bent fork tubes (or no tubes at all) wd not affect this. And if the yoke centers are not aligned, all other bets are off anyway.

I can indeed take the tubes off, and I think I can find a place to check them for straightness. I could probably check them right on the bike, rotating them in the yokes and measuring the span in different positions. And I wish I cd imagine the jig which wd keep everything aligned while tightening up the lower yoke to trap the headlamp ears and pull it up to the stem. I am of course relying on the tubes themselves to do this alignment during the tightening process.
As mentioned earlier, the rim cannot be measured directly to the tubes unless the sliders are removed. Do you think this wd be necessary?

"If you measure the fork tube distance just below the lower yoke, it should be the same as the measurement as it measures just above the sliders."
That is exactly where I found the "taper", the lower measurement being smaller than the upper. I plan to drop the lower yoke and see if I can spot anything wonky about it, and might even put a different one up there, see if anything changes.
Thanks again for your help.
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Re: front wheel offset on disk brake commandos

Postby bucksfizz » Tue Mar 07, 2017 6:43 am

I didn't mean to hi-jack this thread, but I am grateful for all the replies.
I do like the PDF file on the world's straightest Norton - I have saved a copy.
I think I have some additional work to do.
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Re: front wheel offset on disk brake commandos

Postby Madnorton » Tue Mar 07, 2017 12:46 pm

Got a feeling the centre line, which is not the centre line of the bike, around which the MK3 swingarm is manufactured is different to the pre MK3 swingarm, not sure how this relates to the centreing of the wheel in the MK3 swingarm though. Of course the MK3 rear wheel would be offset to compensate, sadly this is not much help here

I think Pete Lovell was also looking at the MK3 frame, cradle, wheels alignment issue back last year.

Also, I notice the re-current O rings in the yokes, with the stanchions removed the fitting is a doddle - put headlamp ears in place, they should balance there and then fit the lower 2 O rings one at a time by inserting them where the stanchion would enter ease it round and then fit the second one, then do the one in the top down through the hole in the top yoke where the tapered portion of the stanchion fits - simple!

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Re: front wheel offset on disk brake commandos

Postby L.A.B. » Tue Mar 07, 2017 1:12 pm

Madnorton wrote:Got a feeling the centre line, which is not the centre line of the bike, around which the MK3 swingarm is manufactured is different to the pre MK3 swingarm, not sure how this relates to the centreing of the wheel in the MK3 swingarm though. Of course the MK3 rear wheel would be offset to compensate, sadly this is not much help here




All Commando cradles are offset to the left of the frame centre line by approximately the same amount (1/8" - 3/16"), therefore all swinging arm fork ends should be offset the opposite way to compensate, otherwise the shocks would lean to the right (viewed from the rear) because the frame is (or should be) symmetrical, it doesn't just apply to Mk3.


http://www.nortonownersclub.org/support ... el-offsets
Commando wheel offset - the definitive answer

I have the definitive answer as to what is offset, how much, and which way!

I set up a 1973 850 on the frame table and verified it was straight. I then put together a dummy engine and installed it with new isolastics, new washers, Hemmings adjusters, and a Norvil head steady. I put both adjusters on the left side, checked the swinging arm in my fixture and then installed it in the frame. I took all the play out of the adjusters and started measuring:-

The frame is symmetrical
The engine/gearbox cradle is offset 1/8" to the left.
The swinging arm is offset 1/8" to the right so the axle pads end up centred in the frame

I then installed the rear wheel:-

The spoke flanges are offset 1/8" to the left as mounted in the arm, so the rim is laced off 1/8" to the right to put the tyre in the centre
The centre of the rim is 3.3/8" from a straight edge laid across the brake drum (not the backing plate

With the stock Dunlop rim, if you sight across the rim on the brake drum side you will see about 1/16" of hub when it's in the right place. In my opinion, front and rear adjusters should be on the same side. Otherwise as things wear and you take up the slop you angle the engine and gearbox in the frame. Since the swinging arm mounts to the cradle, a little one way in the front and a bit the other way in the back and the rear wheel is out of line considerably. The chain will still line up but the wheels will not.

Vernon Fueston (fueston@snowcrest.net) on NOC-L 22nd. Nov 1997
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Re: front wheel offset on disk brake commandos

Postby Madnorton » Tue Mar 07, 2017 3:25 pm

Agreed, I'll get some photos as I have a new frame, cradle and swingarm fitted up without the wheel in place. Strangely, I know of two owners who have had front wheels built for MK3's at the same place within the last 12 months and both were not correct in the forks, one needed a fair bit of movement to correct it. I also have pictures of a rear Campbray in the MK3 swingarm which needed the tyre shaved, but this I can attribute to incorrect spacing as the side wear on the rear sprocket was terrible.

Looking at the above picture, the rear chain also seems to close to the RHS of the chainguard also, maybe a bit of an illusion though.

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Re: front wheel offset on disk brake commandos

Postby batrider » Sat Mar 11, 2017 9:35 am

An easy way to check the fork tubes for straightness when they're off is to roll them side by side together. It is easy to tell if they are bent and it doesn't cost anything. Past advice from hobot.
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Re: front wheel offset on disk brake commandos

Postby Mr. Rick » Sat Mar 11, 2017 11:52 pm

Thank you, Russ. (and Hobot)
I pulled the tire off the rim and found no change with respect to the center of the steering axis, the gap between the rim and the slider on the right side stiil bigger than the left.
I borrowed another ANG triple tree, will swap the lower yoke out for mine and see if this makes a difference.
I intend to pull the forks apart, to check the tubes for straightness, but wd like to know: is it possible to pull the sliders down a few inches after loosening the collars 061137 and removing the anchor bolt 060359? Am I in danger of losing track of that inner fibre? washer NMT814 if I do so? I'd like to see what it looks like measuring from rim directly to the main tubes, rather than to the sliders.
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Re: front wheel offset on disk brake commandos

Postby L.A.B. » Sun Mar 12, 2017 2:36 am

Mr. Rick wrote:is it possible to pull the sliders down a few inches after loosening the collars 061137 and removing the anchor bolt 060359?


If the damper bolts 060539 are removed or the fork cap bolts released from the damper rods, the sliders will drop by approximately 1.5 inches (assuming they are standard fork parts).

If you want to drop the sliders any further, the 011637 collars need to be unscrewed and each slider raised and jerked down with enough force to dislodge the upper fork bush from the slider.
The slider can then be slid off the stanchion/tube if required.




Mr. Rick wrote:Am I in danger of losing track of that inner fibre? washer NMT814 if I do so?


It can stick in the slider or it can stick to the bottom of the damper tube. Unless you intend to remove the sliders completely, the safest way would be to release the damper rods from the fork cap bolts instead of releasing the damper tubes from the sliders as the result will be the same (sliders will drop by 1.5 inches).
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