Wheel Alignment on my 961.

lcrken

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After my crash back in March, with subsequent repairs, the bike just didn't feel right at the front end. So I decided to check the front and rear wheel alignment. I'd not previously checked it, just making sure that the distance from end of swingarm to axle slider was the same on both sides after chain adjustments or tire changes. I used a set of pair of aluminum tubes that I had made for my original Commandos back in the '70s, just needing some more spacers at the front wheel. I discovered that the wheels were out of line by a large amount, and adjusted the axle sliders until the wheels were lined up. When done, the axle sliders were not the same distance from the end of the swing arm, and the difference was large at .325". Now I'm wondering if something got knocked out of line a bit in the crash. I also loosened the top yoke, bounced the front end a few times, and re-tightened the yoke. I had done that earlier while repairing the damage, but figured it couldn't hurt to do it again.

I took the bike out for a spirited ride in the twisties, and it feels back to normal. But, I'm concerned about the large difference in axle slider measurements, and I also noticed that the tire is much closer now to the left side of the swingarm than to the right. Does anyone know if the front of the tire is supposed to be centered in the swingarm? In the original Commandos, the swing arm is not symmetrical, so the left and right gaps to the tire are not the same, Is that also the case in the 961? Or is my bike just bent? :( I'm hoping this doesn't turn into a major chassis checking project.

Picture of the setup I used to line the tires up:

Left Side 1200.jpg


Ken
 

Stephen_Spencer

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Hey Ken, sux that you are still having difficulties - hope you can get it sorted. I know what it’s like to ride with a nagging doubt playing on your mind.

Not the easiest thing to measure, the periphery of the rear tyre to the inner edge of the swing arm. It appears the swing arm gaps (for want of a better term) are not equal. On my bike LHS = 12mm (approx) with RHS (chain side) = 20mm (approx).

Hope that helps

Steve

52C9C303-54EC-406D-8838-31A26D40ADAA.png
D26B0861-0703-41A7-84E8-54B07E3FDC82.png
 

StuartSF2015

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Ken,
Having to have a frame (not a Norton) straightened recently, I empathise with your dilema. Rear wheel position in the swing arm should permit exact alignment of the front and rear sprockets. Check this with a guide, such as a Lazer Monkey or other devise with a pointer that clamps to the rear sprocket, your chain guard will have to come off for to achieve this. Use the wheel adjusters to get the sprockets in line and then check your wheel alignment front to rear. They should be broadly similar, within a mm or so on each side. If the gaps between your guides and the rims of the front wheel are discernibly different, then you probably have a twist in the headstock and or the swing arm as well, as was the case with mine. Specialist firm got the twists out at a cost of £250.00 for me.
Trust this is helpful to you.
 
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Worth checking sprocket alignment with a laser pointer. Ive got the chain monkey branded one, works well.
 

lcrken

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Thanks, Stuart. The measurements you made and the suggestion to check the sprocket alignment are exactly the sort of info I was looking for. It didn't occur to me to check the sprocket alignment, but I will certainly do so.

The part that bothers me most is that the service manual (the later one for EURO4 bikes) specifically tells us to adjust the rear wheel so that the distance from the end of the swingarm to the edge of the wheel adjuster is the same on left and right sides., but mine is now drastically different. In any case, I'll get on with some more measurements to see what I can find. Besides sprocket alignment, I'll pick up some long tram gauges so I can measure distance from axle center to axle center, and compare them when wheels are in line.

Really hoping to not have to do any major chassis work, but will if I have to. I plan to keep this bike until I can't ride any more, so I might as well get it right.

Ken
 

lcrken

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Worth checking sprocket alignment with a laser pointer. Ive got the chain monkey branded one, works well.
Sounds good. I should probably get something like that. I usually just use a long straight edge and some spacers, but that's not nearly as straightforward when there are bike parts in the way.

Ken
 

lcrken

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Dr Johns frame repair in Anaheim, He has all the tables and fixtures to straighten frames, forks, triple trees wheels etc he can get any bike spot on, top man.
Yeah, I've been to them a couple of times, but decades ago. Good to know that they are still in business. But if it is the frame that is bent, I would have to strip the bike all the way down for them to fix it. Hoping to avoid that .:(

Ken
 
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First item I would check is whether the front wheel is central to the forks, maybe a spacer has been missed or swapped sides.
 

cliffa

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Ken, I like your rig !! when you have both wheels aligned how do the bars look? is it possible one of the stanchions is slightly bent? Maybe it would be worth loosening one at a time, spray some lube into the yokes / trees then twist them and see if you feel any resistance as they potentially try to fight the spindle length. Easier than dropping them out.

I love that picture by the way, and have a few non Norton questions :

Is that an extension reel in the net? if so I'm intrigued, how do you get it back in once you've used it?
What is the car?
It looks like you have an English wheel at the back? If so can you knock up some alloy tanks ? :) :)
 
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Well, to be honest, Ive never checked with a straight edge or string. Ive always done it the factory way ie measure from the swingarm edge...but those spreader plates can make it tricky sometimes. I bought the laser alignment tool and Ive been double checking, but they've never been miles out of alignment, sprocket to sprocket. But the next few I get in, I'll get the string out and see how the wheel alignment sits front to back on a few.
 

lcrken

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Ken, I like your rig !! when you have both wheels aligned how do the bars look? is it possible one of the stanchions is slightly bent? Maybe it would be worth loosening one at a time, spray some lube into the yokes / trees then twist them and see if you feel any resistance as they potentially try to fight the spindle length. Easier than dropping them out.

I love that picture by the way, and have a few non Norton questions :

Is that an extension reel in the net? if so I'm intrigued, how do you get it back in once you've used it?
What is the car?
It looks like you have an English wheel at the back? If so can you knock up some alloy tanks ? :) :)

I think it unlikely the stanchions are bent, but it's certainly possible. The left end of the axle hit the ground pretty hard, from the looks of the grind marks on it. The forks don't appear twisted or bent, but I would probably have to remove them for more precise measurement to be sure. I think I would have to put it on the surface plate with v-blocks to make an accurate enough measurement.

I'm waiting for a precision tram gauge to arrive so I can make some accurate chassis measurements. Hoping to find a 'smoking gun" that explains everything.:)

The bar mounts were knocked out of alignment in the crash, but I'm using spacers on the stock bar mounts, along with Rox adjustable bar risers, and with so many movable joints, the bar alignment is easily tweaked in a crash, even if the forks are not affected. You can see what I mean about the mounts in this picture:
Rox Bar Risers.jpg


That is indeed an extension reel in the picture. There is a hand crank on the side of it that turns a friction wheel that reels the cord back in, and it automatically coils itself up in the net. you can see the black knob on the end of the handle sticking up above the case. I've had it for many years, and absolutely love it. It is similar to this one, although slightly different:

Amazon product
The car is a 1959 Studebaker Lark. I'm building a blown Studebaker V-8 engine for it in my spare time. :rolleyes: It's a project with my grandson. We're building it as a combination road and track car, with serious chassis and suspension mods, etc.

The English wheel was a present from my wife. I've experimented with it, but never made anything useful. I have hopes of eventually fabricating some cool stuff with it, but am starting to wonder if I will ever manage that. Hey, it's good to have dreams.

Ken
 

Voodooo

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My dominator rear wheel was so out of wack from the factory it was ridiculous. It was literally 3/16” or 5mm off from side to side.

When going around corners or going straight it always seemed like the bike was dog tracking.

What I did first was measure the swing arm center line to the rear axle center line with a tram gauge.

Then I used a chain alignment laser to make sure the two sprockets were aligned.
I did this without the chain on. This allowed me a more accurate measurement to make sure both sprockets were inline to each other.

But you must make sure all your cush bushings and both sprockets are clean, straight and in good condition. I removed my rear wheel and also checked for straightness along with making sure the rear sprocket was true.

Once I had the rear all dialed in, I ran a string on both sides of the bike. I took a long string and made sure both sides of the bike had the string touching each sidewall of the rear tire on both sides of the tire.

I then pulled those same stings all the way to the front tire keeping each pair of strings the same width apart as the rear. (Rear tire width)

Then I measured each distance apart on the front wheel and compared both left and right sides of the front side walls. Mine was .030 more to the right. I’m not concerned about .030 thousands of an inch. I’d have to turn down one spacer .015 and add .015 to the other side to make it perfect.

The main issue was the rear being so out of wack since day one.
 

lcrken

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My dominator rear wheel was so out of wack from the factory it was ridiculous. It was literally 3/16” or 5mm off from side to side.

When going around corners or going straight it always seemed like the bike was dog tracking.

What I did first was measure the swing arm center line to the rear axle center line with a tram gauge.

Then I used a chain alignment laser to make sure the two sprockets were aligned.
I did this without the chain on. This allowed me a more accurate measurement to make sure both sprockets were inline to each other.

But you must make sure all your cush bushings and both sprockets are clean, straight and in good condition. I removed my rear wheel and also checked for straightness along with making sure the rear sprocket was true.

Once I had the rear all dialed in, I ran a string on both sides of the bike. I took a long string and made sure both sides of the bike had the string touching each sidewall of the rear tire on both sides of the tire.

I then pulled those same stings all the way to the front tire keeping each pair of strings the same width apart as the rear. (Rear tire width)

Then I measured each distance apart on the front wheel and compared both left and right sides of the front side walls. Mine was .030 more to the right. I’m not concerned about .030 thousands of an inch. I’d have to turn down one spacer .015 and add .015 to the other side to make it perfect.

The main issue was the rear being so out of wack since day one.

Thanks for the info, Voodoo.

My suspicion is that mine was also out of whack since day one. It was fun to ride in the twisties, but it did seem to turn in to the right easier than to the left, and also seemed to run wide more in lefts than rights when gassing it out of the corners. But it's hard to be sure because of the recent crash. I should get it sorted out eventually. At the moment, it actually seems to work pretty well, but I worry that the rear axle might be under a lot of bending stress with the adjusters so far out of adjustment. Not to mention wear on chain and sprockets. As soon as the tram gauge arrives, I'll at least be able to check the swingarm pivot to rear axle distance on both sides, as well as distances to the front axle.

Ken
 

lcrken

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Update. I set the bike up again with the wheel alignment jigs, and very carefully adjusted the rear wheel back to the factory setting, with the axle sliders the same length from the rear of the swingarm on left and right sides. I turned he front wheel until it was parallel with the rear wheel, and measured the offset at the front between the jig parallels. With this setup, the front wheel is 7/8" offset to the left. In this picture you can see the 1 3/4" gap on the right side of the wheel, while the left side is just touching the jig. Something is clearly not right. :(

Front Wheel Offset with Rear Wheel Adjusted to Factory Specs 1200.jpg


I was unable to use a tram gauge to check the rear axle to swing arm pivot distance on both sides. I would have to either remove the primary case or make up some offset tooling to do so, and just didn't have the time for that today. Maybe later. I did use straight edges and a digital angle gauge to measure if the wheels were parallel in the vertical axis, and they are off by 0.9 - 1.1 degrees, so something is bent/twisted. I used a pair of bars in the rear axle and the swing arm pivot to check if they were parallel, shown below.

Checking for SA Twist1200.jpg


They measured off by 0.15 to 0.20 degrees, but my measurement accuracy is in the 0.1 degree range, so those measurements aren't too significant, except to say that the difference in the wheel angles is not from swing arm twist. The rear crossmember in the frame just above the swing arm pivot is also parallel to the rear axle and pivot, at least within my measurement accuracy, and measures 1.0 to 1.1 degrees off from perpendicular to the front tire.

It looks likely from all this that I may have something like a 1 degree or more twist in the steering head. A little simple geometry shows that a 1 degree twist at the steering head would give about 5/8" offset at the bottom of the front tire. That's close enough to my 7/8" measurements to make me suspect it as the primary problem, but I really need some more measurements to be sure. With a little more effort, I could tram the axle to swing arm pivot measurements, and check the sprocket alignment.

This is interesting preliminary stuff, but I'd like a little more accuracy and detail. In the old days, I'd just take it to the local Computrack facility, but they've been out of business for a while now. I just discovered that Race Tech, the suspension gurus here in SoCal have a similar frame checking system called MEGA M.A.X., that can check all sorts of frame dimensions with the bike still mostly assembled. They charge $250 for a complete measurement survey, a not unreasonable amount for the labor time it takes. I'll give them a call tomorrow to see if they can also straighten the frame after measuring it. Their web site only mentions measurements, so I'm not sure if they also do the repairs.

I could borrow my friend's precision adjustable frame jig, but I'd have to completely strip the chassis to use it, and I'm only willing to do that if I'm sure it's needed. I kind of suspect that I'll eventually have to do that to straighten the frame, but I'm still hoping for a miracle.

Ken
 

StuartSF2015

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Update. I set the bike up again with the wheel alignment jigs, and very carefully adjusted the rear wheel back to the factory setting, with the axle sliders the same length from the rear of the swingarm on left and right sides. I turned he front wheel until it was parallel with the rear wheel, and measured the offset at the front between the jig parallels. With this setup, the front wheel is 7/8" offset to the left. In this picture you can see the 1 3/4" gap on the right side of the wheel, while the left side is just touching the jig. Something is clearly not right. :(

View attachment 81230

I was unable to use a tram gauge to check the rear axle to swing arm pivot distance on both sides. I would have to either remove the primary case or make up some offset tooling to do so, and just didn't have the time for that today. Maybe later. I did use straight edges and a digital angle gauge to measure if the wheels were parallel in the vertical axis, and they are off by 0.9 - 1.1 degrees, so something is bent/twisted. I used a pair of bars in the rear axle and the swing arm pivot to check if they were parallel, shown below.

View attachment 81231

They measured off by 0.15 to 0.20 degrees, but my measurement accuracy is in the 0.1 degree range, so those measurements aren't too significant, except to say that the difference in the wheel angles is not from swing arm twist. The rear crossmember in the frame just above the swing arm pivot is also parallel to the rear axle and pivot, at least within my measurement accuracy, and measures 1.0 to 1.1 degrees off from perpendicular to the front tire.

It looks likely from all this that I may have something like a 1 degree or more twist in the steering head. A little simple geometry shows that a 1 degree twist at the steering head would give about 5/8" offset at the bottom of the front tire. That's close enough to my 7/8" measurements to make me suspect it as the primary problem, but I really need some more measurements to be sure. With a little more effort, I could tram the axle to swing arm pivot measurements, and check the sprocket alignment.

This is interesting preliminary stuff, but I'd like a little more accuracy and detail. In the old days, I'd just take it to the local Computrack facility, but they've been out of business for a while now. I just discovered that Race Tech, the suspension gurus here in SoCal have a similar frame checking system called MEGA M.A.X., that can check all sorts of frame dimensions with the bike still mostly assembled. They charge $250 for a complete measurement survey, a not unreasonable amount for the labor time it takes. I'll give them a call tomorrow to see if they can also straighten the frame after measuring it. Their web site only mentions measurements, so I'm not sure if they also do the repairs.

I could borrow my friend's precision adjustable frame jig, but I'd have to completely strip the chassis to use it, and I'm only willing to do that if I'm sure it's needed. I kind of suspect that I'll eventually have to do that to straighten the frame, but I'm still hoping for a miracle.

Ken,
Ken,
Miracles aside, you definitely appear to have a twist in the head stock. The good news is that it can be fixed, albeit by a specialist with the right gear to do it.
My twist was easily sorted by Motoliner in the UK. This picture shows their rig and how they set up a bike for checking. Note the ‘spike’ fitted through the headstock to check the headstock angle and the lateral braces to the swing arm pivots to hold the frame square in the jig.

C6010E91-B7E4-43A0-B2A7-87A1E127AAA5.jpeg


They did need me to prep the bike to facilitate them being able to put it straight onto their jig. It took me about an hour to remove tank, seat, exhausts and strip front end folding cables etc back along the frame and securing with cable ties.
B2D94BCE-20EA-41C5-8699-E1EF5C481C02.jpeg


I used their trusted courier to ship it to and fro and spent another couple of hours putting the bits back on. A home check with a couple of straight edges looked good and a trip to the MoT station for a regulation safety check confirmed all was well. No miracles, just a bit of graft, spannering work and the exchange of some ‘beer voucher £s’ All achieved within about 10 days start to finish.
Hope this helps with your solution and it works out as well as my experience.
Good luck
Stuart
 
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