Commando steering shake.

gortnipper · Dec 29, 2020

Another trick is using blocks as stand offs on the front and rear of both the rims for string between them.

tricatcent · Dec 30, 2020

If your bike does that now and it didn't before it must be because of something wearing or has broken. You have fixed the isos already. I don't think you mentioned the swing arm bushings they have to be good on any bike. It may be your head steady. The older ones could crack. Also the rubbers can get really soft. I have a home made tie rod end type. My bike only wobbles a bit when I take one hand of the bars at very low speed when I am signalling a turn. It seems like the really slow speed of the engine pulses through the head steady and causes a slight shake that goes away immediately when I put my hand back on the bars. My bike began to vibrate more a few years ago. I figured it was time to replace the rear isos. I took it all apart and found that everything looked OK. I put the new parts in anyway. When I re assembled everything it turned out my engine was at a different tilt than before and I had to adjust my head steady to fit the new alignment. The bike did run smoother after that so I guess the old iso had sagged on one side for some reason.

On an old Triumph I had a really silly thing happened. I didn't ride it for about 10 years because I thought the swing arm bushings were shot. The bike wobbled as a result. I could feel the play in the back wheel, maybe it was about 1/8" I knew this bike had a dodgy home made swing arm. I parked the bike, I had a lot of other projects to fiddle with. Finally I thought it had been to long and I figured swing arm bushings were not that big a job. I put the bike on the work stand and took it appart. On that bike the nuts that hold the long stud that is for the swing arm were covered over with some plates. It turned out the nuts were loose! I took the swing arm off and inspected the bushings. They were fine. I put it back together with red loctite and it has been perfect ever since. Play in the swing arm causes wobbles that's for sure.

kerinorton · Dec 30, 2020

When the front tyre on my 850 wears on the edges after 2000 miles or so, it will wobble and 30 mph. Its fine above that speed. Its not caused by engine vibration but others have had the same thing happen to them. If you grab your rear wheel and yank hard enough each way, it will move a lot, 3/8 inch plus, but that would be normal and wont be causing your problem. If a front tyre is bad, you only have to remove one hand from the bars at any speed to find it. A bad tyre on the rear probably wont show up unless its really bad.

Dereck

GTCarlos · Dec 30, 2020

Hi All,

Thanks for your continuing input. It's Super helpful !

I measured the rear wheel movement today per the suggestion of Concours and Tricatcent. With the wheel off the ground on the center stand, pulling and pushing as hard as I could on the back of the rear wheel I got between 3/16 and 1/4" total movement. That was measured between the rearmost point of the rim and the muffler. What movement there was felt smooth with no play or notchy-ness, just flex. A friend has two Commandos in the garage that both ride well. Tomorrow I'll compare them to mine for flex, tire wear, etc.

Per Gotnipper's advice, I got a somewhat better check on the alignment. With my VERY makeshift tools it still looked a little off so I adjusted it further (in the same direction as before), moving the axle stop about 1-1/2 threads more. Notwithstanding my vague tooling, it looks prety good now. That said, I don't think it ws ever off enough to cause the low speed head-shake but it was certainly off enough to scallop the rear tire and THAT could (perhaps) cause my problem.

I inspected the shocks which *look* fine. I'll swap them around and see if that has any impact. As it was beginning to rain, getting dark and pushing 42° F, I didn't test ride it but I will tomorrow mid-day and report back if I learn anything new.

Thanks again.

-Danny

GTCarlos · Dec 30, 2020

Oh, also, the rubber mounts in the stock head-steady are less than a year old and they *look* OK. The metal parts are fine; no cracks. I'll try the Dave Taylor head steady again but not until after I've swapped around the suspension and try a new tire. Also, I'll check the swing arm nuts first thing to ensure they're snug. It'll be embarassing but comforting if the problem proves to be that simple.

-Danny

swooshdave · Dec 31, 2020

Don’t change too many things at once between test rides.

RoadScholar · Dec 31, 2020

One point that I don't think has been mentioned is camber angle of the wheel assemblies. If you had to muscle the DT head steady to set the fasteners you may have made the rear wheel think that it is cornering. Aligning the rear to front wouldn't show this up. To check camber you will need vertical reference points; you could build some with angle stock or use a pair of plumb bobs hung from above the bike.

Best.

jan nelder · Dec 31, 2020

RoadScholar said:
One point that I don't think has been mentioned is camber angle of the wheel assemblies. If you had to muscle the DT head steady to set the fasteners you may have made the rear wheel think that it is cornering. Aligning the rear to front wouldn't show this up. To check camber you will need vertical reference points; you could build some with angle stock or use a pair of plumb bobs hung from above the bike.

or get wheels lined up and held, then shim centre stand to get front wheel vertical using a good spirit level held lightly across equivalent parts of tyre rim, then see if rear wheel agrees... will show significant discrepancy if it’s there.

Craig · Dec 31, 2020

You can pick up cheap line laser for $20 or less at most places that sell carpenters tools , they work great

maylar · Jan 2, 2021

gortnipper said:
Use a 4' fluorescent tube to check.

4 ft isn't long enough to straddle both wheels.

Torontonian · Jan 2, 2021

maylar said:
4 ft isn't long enough to straddle both wheels.

Lasers are super cheap from China now.

GTCarlos · Jan 2, 2021

Torontonian said:
Lasers are super cheap from China now.

Hi All,

I'm not clear on how I'd use a LASER. I'm guessing I could set up some kind of jig but I'd rather not re-invent the wheel as they say. Any pictures, designs or descriptions would be super helpful. I'm sure I can find a functional one pretty easily to test with.

With respect to rear wheel movement, I checked two other Commandos for play at the rear wheel. Grabbing the rear frame rail and moving the back of the wheel as hard as I could to and fro, BOTH bikes had at least twice the movement mine has and both had significant play resulting in a 'clunk" when the wheel was moved side to side. Of course both ride straight and true with no wobble so I'm ruling that out.

Next step I'll check the swingarm nuts in the morning and look for camber problems with a plum bob and my eyeballs. If camber IS the/a problem, how would I correct it? Time to visit the frame shop? dig in to the front suspension or ?? Last, I'll swap out the rear tire and, if it's not raining tomorrow, do a quick road test. If that doesn't fix anything I'll swap the shocks out from another bike. I'll report back then.

Meanwhile, thanks again for al the ideas and help.

-Danny

kerinorton · Jan 3, 2021

You could get someone to ride behind you and watch what happens. I never really had a problem like yours but a mate was following me once and told me my bike was crabbing. I had not aligned the rear wheel correctly and it was that obvious to him.

I once had a problem like what you have described, although mine was at his speed. i mentioned it to a Norton specialist one time and he asked me if the handle bars went crazy if I took one hand off. That was true and he told me it was the front tyre. My faulty front tyre ran true as a die when checking it out when stationary. Yet is was the problem. Did your problem start after replacing your front tyre.
Maybe fit a new front tyre and see if the problem has gone. You seem to have checked everything else [ so I suggest there may not be anything wrong with your bike ] so go back to basics. Tyres are cheap, whereas your time is valuable.

Dereck

Torontonian · Jan 3, 2021

kerinorton said:
You could get someone to ride behind you and watch what happens. I never really had a problem like yours but a mate was following me once and told me my bike was crabbing. I had not aligned the rear wheel correctly and it was that obvious to him.

I once had a problem like what you have described, although mine was at his speed. i mentioned it to a Norton specialist one time and he asked me if the handle bars went crazy if I took one hand off. That was true and he told me it was the front tyre. My faulty front tyre ran true as a die when checking it out when stationary. Yet is was the problem. Did your problem start after replacing your front tyre.
Maybe fit a new front tyre and see if the problem has gone. You seem to have checked everything else [ so I suggest there may not be anything wrong with your bike ] so go back to basics. Tyres are cheap, whereas your time is valuable.

Dereck

Yes to new (matched brand and type) tires. Modern new tires make a huge noticeable difference.

swooshdave · Jan 3, 2021

GTCarlos said:
Hi All,

I'm not clear on how I'd use a LASER. I'm guessing I could set up some kind of jig but I'd rather not re-invent the wheel as they say. Any pictures, designs or descriptions would be super helpful. I'm sure I can find a functional one pretty easily to test with.

With respect to rear wheel movement, I checked two other Commandos for play at the rear wheel. Grabbing the rear frame rail and moving the back of the wheel as hard as I could to and fro, BOTH bikes had at least twice the movement mine has and both had significant play resulting in a 'clunk" when the wheel was moved side to side. Of course both ride straight and true with no wobble so I'm ruling that out.

Next step I'll check the swingarm nuts in the morning and look for camber problems with a plum bob and my eyeballs. If camber IS the/a problem, how would I correct it? Time to visit the frame shop? dig in to the front suspension or ?? Last, I'll swap out the rear tire and, if it's not raining tomorrow, do a quick road test. If that doesn't fix anything I'll swap the shocks out from another bike. I'll report back then.

Meanwhile, thanks again for al the ideas and help.

-Danny

I got a laser level for Christmas. You just gave me an excuse to try it out.

I don’t know how you ever get these lined up right but what I think you do is set the front wheel dead ahead. The set up the laser so it’s exactly parallel to the front wheel. Measure from the rim not the tire.

Then see if the rear wheel is parallel to the laser line.

At least that’s my best guess.

gortnipper · Jan 3, 2021

swooshdave said:
I got a laser level for Christmas. You just gave me an excuse to try it out.

I don’t know how you ever get these lined up right but what I think you do is set the front wheel dead ahead. The set up the laser so it’s exactly parallel to the front wheel. Measure from the rim not the tire.

Then see if the rear wheel is parallel to the laser line.

At least that’s my best guess.

I used one of those to true the rear wheel to the spine. Worked well but you have to set it up from rear above.

swooshdave · Jan 3, 2021

gortnipper said:
I used one of those to true the rear wheel to the spine. Worked well but you have to set it up from rear above.

I think you have to be way off to affect the tire wear and handling.

Torontonian · Jan 3, 2021

swooshdave said:
I got a laser level for Christmas. You just gave me an excuse to try it out.

I don’t know how you ever get these lined up right but what I think you do is set the front wheel dead ahead. The set up the laser so it’s exactly parallel to the front wheel. Measure from the rim not the tire.

Then see if the rear wheel is parallel to the laser line.

At least that’s my best guess.

The rear wheel is always a bit off. The front is chocked up tight in a clamp I assume. (Never assume anything.) No known history of crashes or drops ? Nice Laser BTW. Helps you build a nice straight garage for the Norton too.

swooshdave · Jan 3, 2021

Torontonian said:
The rear wheel is always a bit off. The front is chocked up tight in a clamp I assume. (Never assume anything.) No known history of crashes or drops ? Nice Laser BTW. Helps you build a nice straight garage for the Norton too.

I’m not trying to align it in the picture. I’d do it on the ground and on the centerstand. I just wanted to illustrate how one might use the laser.

Deets55 · Jan 4, 2021

Level bike by shimming under center stand
Locate centerline of bike by setting laser on center of triple tree, along center of backbone and center of rear hoop. If the laser is centered between the hoop and on center of triple trees it should be right on the center line of backbone. If not there is a problem.

Use a framing square to get some offset lines to check location of rear axle

Use a plumb bob to check distance to offset line.
If the center of both sides of the axle are of equal distance to offset line then the axle is at right angles to frame. If the centerline of the tire is on the laser line then your wheel offset is correct. Put a regular bubble level vertically on the top and bottom of the wheel/tire. If it reads good you are set. The back wheel and tire are now in the correct location in relationship to the frame. If the front wheel has the correct offset and centered between the fork tubes you should be good to go. If anything on your bike is bent or damaged nothing will ever line up correctly but this will still get you close enough.

EDIT: FWIW, I did all the measurements with tank and seat off

Commando steering shake.

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