Commando steering shake.

robs ss said:

Even if that message is to let go of the handlebars and, to quote you, "wait until the bars stop thrashing about before you grab them again or you might go straight over the front and end up on the deck."

Hmmm? Do that or fit a damper? You pose a very difficult question - not!

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The damper should not need to be there under normal circumstances. It's function is to prevent the tank-slapper when the front tyre breaks free. If you need a damper when you are touring, you are riding far too fast or you have got a serious problem. On a race circuit, some bikes shake their heads as you accelerate out of corners, a damper can stop that. Also if your brake is set up to be one finger operation and you chirp the front tyre, the bike can go into the tank slapper, the damper stops that. On a race bike, if the brake is not one-finger operation, you will usually be too slow. Riding on public roads is similar but different. When you race, you are not half-asleep. If you have a moment, you get time dilation, so you always have plenty of time to react. With road bikes, the grip around the heart is bigger because you are not expecting.

I read somewhere that Herb Becker had tricked the rear isolastic mount on Doug McCrae's race bike. If you fit bronze bushes in place of the silentblocs on a Manx Norton, there is a difference in the feel. With a Commando, the handling can depend on the head steady - NOT GOOD !

Sounds like something is off for sure. Both my Commando’s go down the road straight as an arrow. I had a short wheelbase BMW R75/5 that had serious weave and wobble issues. It high sided me at 80 mph a couple years ago. The early /5’s where more prone to speed wobble but I had hit a deer a month before the incident. Visual inspection looked good but I later found that the forks and frame were bent from the deer impact which intensified the speed wobble.

Check alignment. Then check to insure the frame is not bent. Then check wheel bearings (common result of weave). Whatever it is, something is off. This isnt a common issue for Norton’s and should be taken seriously. Trust me on that.

Hi All,
I ordered up a set of new steering head bearings and a set of front wheel bearings for the wiggly Commando today. The existing bearings feel fine but I figure a tiny flaw on the head bearings can be magnified by it's long arm to the axle so it's worth a try. Anyway I'm running out of possibilities and they're both fairly in-expensive and fairly easy things to do.

The 3.25x19 tire being smaller and lighter, definitely lessens the symptom (vs. the 100/90-19) so I'm persuaded the problem is in the front end of the bike. If the new bearing sets don't fix things, the remaining tasks are new Rear wheel bearings and then new swing arm bushings. Both feel perfect so I'm avoiding that work and expense as long as possible. If I get that far and I STILL have a wobble, I'll start dismantling the bike to see if the swing arm and /or the frame are bent.

Last, a quick correction: The shocks are Hagons, not ICONs and the head bearings are regular sealed bearings, NOT tapered rollers. It was late when I wrote that. My muttled brain was thinking of a different bike.

I'll report back when the new stuff is installed and tested.

Thanks as always for your collective ideas and help.

-Danny

GTCarlos said:

Hi All,
I ordered up a set of new steering head bearings and a set of front wheel bearings for the wiggly Commando today. The existing bearings feel fine but I figure a tiny flaw on the head bearings can be magnified by it's long arm to the axle so it's worth a try. Anyway I'm running out of possibilities and they're both fairly in-expensive and fairly easy things to do.

The 3.25x19 tire being smaller and lighter, definitely lessens the symptom (vs. the 100/90-19) so I'm persuaded the problem is in the front end of the bike. If the new bearing sets don't fix things, the remaining tasks are new Rear wheel bearings and then new swing arm bushings. Both feel perfect so I'm avoiding that work and expense as long as possible. If I get that far and I STILL have a wobble, I'll start dismantling the bike to see if the swing arm and /or the frame are bent.

Last, a quick correction: The shocks are Hagons, not ICONs and the head bearings are regular sealed bearings, NOT tapered rollers. It was late when I wrote that. My muttled brain was thinking of a different bike.

I'll report back when the new stuff is installed and tested.

Thanks as always for your collective ideas and help.

-Danny

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Are you sure it's a Norton Commando?

Yeah, Very funny... Mostly sure.

I have gone to the garage to work on it, parts and tools in, to return home hours later having made impressive progress on different bike altogether. More a question of promiscuity than loss of focus. I hope. Mental acuity? Huh?

Let's take a poll; What's the average age of Norton owners today and, for that matter, owners on this list?

If you raise the bike and spin the wheels with a pointer near the rims, you might find one of them is running out of true. Or you might have a problem with the way the tyres are seating. If you get some types of oil on your tyres, it can change the rubber and give you a bulge. Even if it does not cause that, the change in adhesion as the wheel rotates, can change the feel of the bike.

GTCarlos said:

Yeah, Very funny... Mostly sure.

I have gone to the garage to work on it, parts and tools in, to return home hours later having made impressive progress on different bike altogether. More a question of promiscuity than loss of focus. I hope. Mental acuity? Huh?

Let's take a poll; What's the average age of Norton owners today and, for that matter, owners on this list?

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You have got to be joking. I am nearly 80, and I can out-ride and out-think most of the much younger guys in Period 4 historic races. It is no good getting old, if you don't get smarter. There is one guy who does not ride often these days - Jeff Curley is pushing 90. If you thought you could beat him, you would be really kidding yourself.
I had to laugh - one of my friends thought he was a good rider. He lined up on the start grid with my old Triton 500 and looked around at all the silly old bearded idiots. He thought he would go very well. Then he found out that he did not know how to ride a motorcycle. He still laughs about it.
You have probably seen 'World's Fastest Indian' - did you think Burt Munro was an idiot ?

Ok back to the beginning.... you said it was fine but thenbegan to shake its head... have you checked the integrity of the swing arm spindle? Never heard of one breaking but ...

oldmikew said:

Ok back to the beginning.... you said it was fine but thenbegan to shake its head... have you checked the integrity of the swing arm spindle? Never heard of one breaking but ...

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I agree with the point that it "started" doing it
Something has altered rather than frame damage etc
I look forward to reading what it turned out to be

Hey Acotrel,

Yes, actually I was joking. A bit lamely it seems but so be it. That said, I find that Riding Skill and recalling where I left my keys, are apparently, different mental categories. At 62 I'm usually the youngest person on any given ride. Most of my riding friends are extremely experienced, dedicated riders and I seldom fail to learn something trying to keep their "Old Man" pace. As I've aged, I have gotten slower but I like to think it's due to my changing values and common sense not incipient incapacity.

I haven't been on a track in 3 decades so "fast street" is as hot as I get these days. In 2018 I had the pleasure of joining a large (i.e. 26 bike) tour that ran 2 days through the back-roads of N. California. All 1975 and earlier bikes. I seldom ride with more than 3 people so I didn't know many of the participants. I was flattered the first evening to overhear several comments and conversations about "Who is that guy on the GT? He's fast". I was keeping a good pace although I mostly credit the bike and the trust I've developed in it over 40 years.

Back to the Norton; The front wheel was a little out-of round and the rear had a couple of loose spokes. It didn't look significant to me but I nonetheless had them both trued and tensioned by a pro. Both run true now, free from run-out and with no loose spots. I have re-balanced both wheels, moved the tires and ultimately replaced both tires with new Avon RoadRunner 2s. Both new tires run true on the rims. A big clue for me was that when I replaced the front 100/90-19 with a smaller, lighter 3.25x19 it reduced the intensity of the shaking symptom a lot. Less mass resulting in less momentum of the shake I assume. It still shakes in the exact same speed range, about 38-44 MPH indicated. The wheel bearings *feel* fine but for lack of a better idea, I have new front ones coming and I'll replace them some time next week. Same with the steering head bearings. They feel fine but new ones are on their way.

If that doesn't solve the problem it's swing-arm spindle and rear wheel bearings. Again it *feels* fine static now. Shaking the wheel side to side as hard as I can with the bike on the stand betrays NO movement or clunking. That said, after wheel bearings I have NO other ideas of where to look so I'll do the swing-arm.

Thanks again for your collective insights and ideas. I look forward to reporting my findings when I solve this one.

Stay safe out there.

-Danny

Try to borrow another wheelset to try. I'd also check for the correct offset on the rear wheel.

It almost seems like my post #78 about balance is acknowledged rather than ignored. Loose spokes wow loaded with 400+ lbs dynamic wobble wobble?
If you can remove the wheels and independently spin them up on unrestrained test axle and drive them some how, maybe air gun blown?, will show imbalance when it hops up and down or rocks side to side. Unwanted energy can help make the tail wag the dog!
I do not particularly believe misalignment of perfect straight wheels/rims cause wobble. Yes hands off tracking "will" be adversly affected.

If this shaking just all of sudden started for no apparent reason and shakes at all speeds, i would look for a ply separation in the front tire.

Hummm. The bike tracks fine, except when wobbling. The idea of spinning up an unrestrained wheel to 45 MPH would be a great test but would require a set-up I lack the resources to create. Maybe back-burner that idea for when I get really desperate.

Borrowing a different set of wheels is an idea I like. I tried the 4 Norton people I know well enough to ask and who live near enough to be feasible, but it turns out I'm the only person in the county still running drum brakes. Any volunteers in the San Francisco Bay Area (I'm in Oakland)? I'd love to borrow some (drum brake) wheels for 20' of testing. That would definitively rule out wheels or prove them guilty.

Last, wheel offset; Is there a spec. for dish in a drum brake era wheel? The guy I had true the wheels has been working on these bikes since they were new ( and before). I didn't ask him to measure anything but he was clear as to why I'd brought the wheels in and he didn't mention that there was anything conspicuously off.

The new bearings arrived today. I'll get to that task in the next few and report back. Cross your collective fingers. .

Thanks.

-Danny

jsnorton said:

If this shaking just all of sudden started for no apparent reason and shakes at all speeds, i would look for a ply separation in the front tire.

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Sadly, I've already inspected, re-balanced and then replace both tires. It only shakes between about 40-45 mph. Turns out I use that range a lot more than I would have guessed.
Thanks.

-Danny

Good luck with your process ! only way to sort it , each step might eliminate issue or you move to next .... bike will tell you and make your day