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Discussion Starter · #1 · (Edited)
Has anyone ever experienced it? A few years ago I had one bike that did it at higher speed rates (Honda GL1500) and I could never figure out what was causing it. Never crashed, just let off the throttle and it would go away as I slowed. I changed the tires and bead balanced, replaced the steering head bearings, added a fork brace and it still would do it. Since it only occurred at above legal speed limits, it didn't worry me too much because it always did fine at all other speeds. What made me think about this is that it happened to a rider here in central Florida earlier this week. Its happened to Honda's, Harleys, BMW's and other brands, so its not a brand specific problem, but it does seem to be a heavier bike problem. Sometimes it can be a front wheel wobble or a rear wheel. In 2012 or 13 the French police discontinued the use of Honda's ST1300's as their police bikes because of a couple of their officers deaths from this problem. Honda did some extensive testing and attributed the problem to uneven weight distribution in the hardside luggage. For those of you who don't know about this issue, this is a video of it happening to a rider as he merges onto the interstate, it doesn't end well. (Warning, video is pretty hard to watch).
Article & Video: https://www.sacramentoinjuryattorneysblog.com/death-wobble-motorycle/
 

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Its the same thing as trailer sway. With a trailer loaded too light in the front, it will whip like Zorro is in charge. One suggested corrective action is to shift your own weight forward as much as you safely can. On a big cruiser, I can see that not being an easy thing to do.
 

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Good question!

The Honda Elite 150D I rode some 200 miles offroad on had a mean death wobble on pavement at legal speeds. I mean, you literally couldn't let go of the bars while riding it it bad. Thankfully the front end weighs nothing on those so overcoming it was effortless. It just meant you couldn't let go of the bars. I take it my death wobble was caused by the fact the forks were bent, frame bent, and probably the steering head was bent. But everything was put together and serviced, so it wasn't going to fall apart or anything. I rode it anyway and it did the job well until the engine died.

But a bike that's all in one piece, serviced, not bent up, and isn't a junker? Beats me.
 

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Nobody really knows the answer, Zeb. There are more theories out there than a bag full of marbles. I experienced one years ago on my Honda 750. Not nearly as sever as the video, but enough scare the **** out of me, and make me wonder how bad I was going to get hurt. I did like you and slowly let off the throttle. Very slowly. I stuck my feet out to the sides to catch some wind and that seemed to stabilize the wobble somewhat. I will say that I was exceeding the speed limit by a great deal.

Once I got home, I stripped the front end down, greased the neck bearings, and tightened the triple tree a little more than required. I also lowered the front end by an inch. I slid the fork tubes up to where they extended over the top triple tree. I never had a problem after that.

Maybe, just maybe, each bike is different and the rider has to play 'guess and gosh' with modifications until the wobble goes away.
 

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My Goldwing 1500 would do it if you took your hands off of the bars. It also handled like a truck.
I got rid of the damned Dunflop tires that were on it and put a Michelin Commander II on the front and a car tire on the back.
Bingo. No more wobble. I can take my hands off of the bars at any speed. Previous owner has seen me do it and is amazed.
 

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I've experienced high speed wobble a few times but it never got to the "death" stage.

Seemed to fix it on my Royal Enfield by bleeding off 8 psi on the front tire, pushing it from 6 over to 2 under spec. This increases the width of the contact patch.

Also had it with a Honda CB450 when I added a large fork mounted batwing fairing. This resolved itself over a few days, as the fairing "settled" and adopted a less vertical position under the steady wind pressure it was being subjected to.

Things that can affect wobble are:
rake and trail
weight distribution including rider gear and accessory items
tire diameter ( which affects trail)
tire rubber formulation and tread pattern
air pressure distribution on bike especially fork mounted items

Basic rule of thumb is: if you have it now and didn't have it before, put things back the way they were. Corollary rule is: make changes to your bike one thing at a time. In the real world, this is a very complex phenomenon, that includes a lot of factors.

Here is a link to a site that does some basic analysis of the physics along with animations of the basic oscillation modes. Vibration Modes of Motorcycles

The last one is kind of funny to me. Who would have guessed that a bike could just fall right over?
 

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My Yamaha with the factory windshield will wobble at 80+MPH if I'm around a couple semi trucks. Seems like the wind currents battering me back and forth, somehow start that little quiver in the bars that, if I don't back off, gets worse.

Since I replaced the windshield with a bat wing fairing, I haven't felt that little quiver that leads to a tank slapper. Maybe the stars just haven't lined up yet, but so far, so good. :)
 

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I haven't experienced a wobble yet, but based on a video I saw, the way to stop the wobble while riding is to lie down on the tank.

This is my 15th post (Yippee!), so I'll put up the video I'm referring to in the following post.
 

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The Murray Walker wobble has been brought up in the past. It does not exist.

The guy in the video has one hand on the bars when the wobble starts. He also has mods to the bike, so it would be hard to figure out what was the problem. He does have a lot of gear on the back. It is hard to see what he has on the front, and if the angle of the dangle has been messed with.

It is not a tank slapper. It is a wobble in the video. A wobble can start with tyres following a squiggle in the road, back eddies from the wind around front screens, disturbed air around read bags and things. And the tyres, and the suspension. Is the back wheel following the front for instance. Are the forks twisted. They will be now.
The only bike I get a wobble from, is my 79 XS1100, and only when I have the side car attached, and only when I have one hand on the bar, and only at low speed. Nothing else I have ever owned, or known anyone to own, has wobbled like in the video.

I had one tank slapper, but not full on, at the track on a bike the handled extremely well. Going as fast as possible around a corner i had been around hundreds of times before. My only guess is the back end broke loose, causing a direction change, and a rearrange from the guidance system. I did not auger in. Can not remember which gear I was in. Maybe second, and maybe around 70 mph.

UK
 

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My 07 Electra Glide would do it on long sweeping curves. Fortunately it was the kind that more throttle would work to get out of it. That's not something the average rider would think to do. More throttle doesn't work for all cases but it did in mine. Kinda hard to do when you are already doing 80mph and in a curve but you do what you got to do. This particular wobble was due to a mechanical issue HD knew about and corrected in 09 with a frame change. I corrected it by going to Indian.:grin: :grin: :grin:
 

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My 79 XS11 does not feel stable at speed around around large sweepers that we find on a freeway, and exit ramps.
My triumph is most stable doing the same thing. This is part of my reasoning for selling the Suzuki.
Some bikes like Yami, have front forks that are too narrow. A fork brace helps.
Some bikes prefer a particular brand of tyre. I will stay with Michelin on Noddy the Triumph.
I have a new set of Syncho sp? for Laramie.

UK
 

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Every mechanical system, and even every solid object, has multiple resonance frequencies, at which it is inclined to oscillate. Moving through the air creates pressure loads that supply energy, as does friction with the roadway. If this energy can be released by oscillating, the bike is inclined to oscillate at it's resonance frequencies. These are usually low frequencies, but even 10 hz is far too fast to actively control with muscle power. Changing weight distribution or speed are the best options to combat wobble in the moment, in my opinion.

I'm not sure that the following is true, but it's my gut feeling that the mechanical resonance frequencies are lower than the input energy excitation frequencies under most conditions. The faster you go, the more gyroscopic effect builds up, and this provides more restorative force to the steering, which increases the resonance frequency of the mechanical system. If at some point the resonance of the mechanical system reaches the frequency of input energy field, you get oscillation.

With more time to investigate the situation, changing the parameters I listed above can eliminate or reduce the problem.

Adding mass to the bars/forks will lower the resonance frequency, while removing mass raises it. The further the mass is from the rotational axis, the most bang for ounce you will get from the mass, because the rotational inertia increase with the distance the mass is from the axis. Bar end weights might be a very effective way to lower resonance frequency, by increasing system inertia. As an experiment, one could try riding with those "heavy hands" workout wrist bands that have the sand or lead shot in them.

Softer rubber tires adds more damping, as does adding a steering damper, or a friction brake on the steering head like some bikes had back in the day.

Increasing tire diameter increases trail, which gives more restorative force to the steering.
 

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My first bike was a TU250x. I didn't care that in a strong headwind I couldn't maintain 70MPH or it didn't have much passing power at 70MPH, but the reason I sold it was because it liked to wobble some at 70MPH, which was a bit unnerving for a new rider. Had it not wobbled I'd probably still be riding it now as I liked it otherwise. I changed the tires to a different brand, but that did not fix the wobble. The bike I bought after the TUX, my Moto Guzzi Nevada, and my present Honda Forza are both rock solid at 75MPH. I don't think it's a size thing either as I've got a friend with a Sportster that stays off the freeway because of wobble.
 

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I had one bike that would wobble. About 65 mph & up my 1981 Suzuki GN400 would wobble badly if leaned over hard in a corner at full throttle. First time my hands came off the bars & I almost crashed. It stopped once I coasted down to around 50. At the time I had heard of tank slappers but hadn't experienced that before & didn't know the things I could have done to fix it.
 

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Discussion Starter · #16 ·
I thought I'd update this thread that I started last month after finding this old video that was made by Dunlop tire company. The video is old, but it has some interesting information about some of the causes and how to handle it if it happens to you. I found it interesting.


 

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The video does raise some interesting points. A few of my own.
This Dunlop video mirrors the Murray video above. Murray worked for an advertising company that had the Dunlop contract.
At the time of making the video, Dunlop were making tyres labelled TT100. These were tyres that were on production 750cc bikes that had lapped the IOM at 100mph plus. I used them on my production bikes at the track. I also used a Dunlop triangle tyre on one of the race bikes. I did not like it. Dunlop offers a riding cure, but no tyre cure, which I find strange.

I used to sell Kawasaki, but had moved to Honda when the 900 came out. My friend Vic never mentioned any wobble or weave with any 900 he sold. I rode alongside one at about 100. None of the Honda 750 bikes I sold, experienced a wobble or weave that I know of. I am sure that from 1971 to 1976 someone would have said something.

So put me in the sceptical ( skeptical for US readers ) department. Today at the bike gang meeting, some of the bikes in the video were present. Moto Guzzi, BMW and Norton. I have an XS1100 which is a bit newer than the video, but a prime candidate for wobble and weave, because the front forks are too narrow, and they flex.

Noddy my Triumph Trophy, does not like the rear top box. It weaves at about 90 plus, but nothing like the bikes in the video. I do not use the top box.

UK
 

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My 07 Electra Glide had that type B wobble at 80mph but as the tires wore it began happening at 75mph. That is in slow sweeping curves I might add. Never happened on straights. Acceleration is what I used to get out of it as I couldn't easily add weight. Or maybe that sweet young thing I wanted to use to add weight is what my wife objected to. Anyway, I had Dunlops on that bike but sold it before needing a third set of tires to see if a different brand had the same problem. But I was told it was a mechanical issue and that's why HD changed the frame in 09.
 

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High speed wobble, or, I guess "weave" is the preferred term for when the entire bike starts oscillating, is such a complex phenomenon that even state of the art computer modeling is not sufficient to explain it. You can see from the video how a change in rider weight distribution can eliminate the issue. Similarly, a change in tire characteristics shape or softness, or rake, or trail, or steering damping or rotational inertia.

The most difficult to understand or predict factor, in my opinion, is the idea that slip stream eddys and vortices contribute. If the speed of the vehicle creates turbulence that is breaking off rhythmically at a harmonic of the resonant frequency of the mechanical system, it will excite the weave mode. This is why adding even an empty trunk or panniers can change weave behavior, even before much mass distribution is changed. What's a sure, quick way to change the slip stream profile? Lying down on the tank, which in one stroke eliminates a lot of frontal area and moves the center of gravity forward, weighting the front tire.

Those 70s test riders had some guts! I wonder what effect filling my shorts would have on high speed wobble?
 

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Tire type can make a big difference.
When I researched what new tires I was going to put on my Kingpin I found out interestingly enough that it was highly recommended NOT to put radials on but only Bias ply, which is what it came with, while almost all other Victory bikes came with radials. I searched online and found many people who put on radials had issues with speed wobble on Kingpins, not all, but many of them. People with saddle bags seemed to be particularly vulnerable, a few stated that their bike wobbles with bags, not without them on radials, but I have yet to see a person who had wobble problems on a Kingpin on bias tires. It was an easy decision for me to put a set of bias ply Commander 2 tires on mine, and it's perfectly stable at any speed.
 
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