Exactly.
I experienced a speed wobble precisely once, on a Kawasaki triple and at low speed. I stopped and checked things over. It turned out the steering head was slightly loose and the additional weight of a pillion passenger had created an instability.
Adjust steering head, a 15 minute job by roadside, problem disappeared.
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What makes it do that? The wheel wants to run straight, that’s what makes a motorcycle stable. As you go faster, the force pulling it straight goes up. If it gets knocked to one side (say by a small rut or bump) that force pulls it back to center, but the steered mass (bars plus wheel plus fork plus added windscreen) has momentum and can go past the center and over to the other side. If there is enough momentum, it swings farther to the other side than initially deflected, then goes back even father, building up as shown.
Why doesn’t every bike do that? Keeping steered mass low helps, as does having “the right” amount of trail (to much = high corrective force, to little = not enough self straightening). And some bikes even have steering dampers to actively prevent it.
My guess is the guy was running “raked trees” that push the front wheel out for a longer look, but actually decrease trail and stability, and also had an aftermarket windshield.
Most riders, in some situations.
Pretty much every bike I’ve ever owned could be provoked into head shakes if you poked it just right. Usually they’re mild enough that a slight amount of pressure on the bars will damp them out, but I’ve had a few lock-to-lock tankslappers (mostly caused by strapping too much luggage onto the back of cheap old bikes with half-knackered suspension).
My current one is a shiny new thing that corners beautifully, but it will still shimmy a little if you’re riding hands-free; the strong engine braking throws the weight forwards a bit too much.
It’s why a lot of sports bikes are fitted with steering dampers; the combination of fast steering (i.e. forks with minimal rake and trail) and enough power to lift the front (thereby dramatically altering the weight balance) makes the occasional wobble almost inevitable.
But, yeah, in this case it was probably the result of an incompetent home mechanic mixed with a rider too daft to realise he had a serious problem. A bit of wobble is no big deal; a positive-feedback escalating wobble is catastrophic.
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It’s pretty important with a speed wobble not to be gripping too tightly also, it is about riding form. The bike wants to correct itself, you kind of have to learn the counter-intuitive thing and not try to muscle it under control while throttling down calmly.
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In Europe it is common even on motorways - call in that someone is driving dangerously or doing something else unsafe and a patrol will certainly be dispatched to check it out.
False report is punishable and when someone calls from a cellphone it is trivial to identify where is the call coming from so most people won’t just fool around - it usually is serious. Be it an accident, road raging idiot brake testing people, or someone who seems to be impaired, either because they are drunk/drugged or simply unwell.
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Gummikuh
Generic term for any BMW motorbike of the pre-GS era, or to be precise, before BMW introduced the telelever system. They have a tendency to wobble, but it’s usually not that critical as the 2-cylinder boxer has a low centre of gravity.
Another half mocking/half insulting term of recent years is Hängetittenguzzi. I’ll let you work this one out for yourself.
As to the video1), my 2 cents are
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Protective clothing. Look into the stuff by Rukka or BMW (often manufactured by Klepper). Modern synthetic fibres can be more wear-resistant than leather, need less maintenance than leather, work far better in the rain and in combination with a Gore-Tex membrane or similar are more comfortable. Most manufactures offer “airflow” models; they come with openings you can open (and close) that let the air flow through your jacket and trousers.
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Never try to get up while you’re still skidding along the road after a dismount. This will only result in a somersault that might injure you more than the dismount itself. Especially if you land on your head, your helmet can’t protect your cervical vertebrae.
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While I’m at it: don’t wear a backpack. If you fall off, there’s a good chance you’ll land on your back and unless all you’ve got in that backpack is a fluffy pillow, your spine will bend like a bow. The wrong way. Get a topcase or saddlebags or strap your bag properly to your bike; there is enough off the shelf stuff that will do the job.
Disclaimer: 1996 Honda XRV 750 “Africa Twin” with a few modifications. Michelin Anakee tyres. Hepco&Becker topcase2). BMW clothing, about the same age as the bike, a bit scoffed now here and there but still does the job, plus additional Ninja-Turtle-style spine protector. Uvex helmet.
1) Did I mention that I hate vertical videos? 2) I've stopped using the side-mounted cases after ripping off the side-view mirror of a Fiat in a hairpin bend at Passo Gavia. But that's neither here nor there.
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They suffer from Vertical Video Syndrome.
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Help me out here; why am I supposed to watch this? Schadenfreude? Watch this guy crash his motorcycle and get badly injured! Ha ha ha! I don’t get it.
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Hopefully some young biker will see it and realise that no, a high speed wobble is not just something to be ignored till it’s too late.
It’s utterly amazing what some kids will do until someone explains the consequences to them. I once took a look at an old Norton ES2 someone had bought - the inner tube was actually poking out through a slit in a sidewall, several spokes were broken, and the headrace was loose. He was intending to fix this “when he got around to it”. A brief lecture of the “oh shit you’re gonna die” variety convinced him to take it a little more seriously.
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And they say Germans have no sense of humour.
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Yep, looks like all the re-education programmes after WW II worked after all.
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That’s a fair point, I suppose. I’m not sure that the person who would ride such an unstable bike at speed is going to learn anything from watching this guy go down. There’s a show on MTV that’s kind of the masochistic version of Funniest Home Videos, where it seems the whole point is to laugh at people doing stupid things and getting hurt while doing them.
Yet there’s always someone else who is willing to try riding down the stairs in a shopping cart.
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In the late 1990’s, I bought a 1985 Suzuki GS450E. It was designed for skinny tyres with inner tubes, but the previous owner had wanted to put modern tubeless sporty tyres on it.
So he cut the valve off the inner tube, glued it in place, threw away the rest of the inner tube, and added a bit more glue to help the tyre seal onto the not-designed-for-tubeless-tyres rim.
I’d ridden it about 100km at highway speed before I realised what he’d done.
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Here’s another winner in the motorcyclists hall of fame.
According to the reddit thread where I found it, both the motorcyclist and the driver of the car he hit received a citation, the driver for failure to look before turning.
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BTW, a reminder from last week about how to deal with steering wobbles:
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Thanks for the article! I have 650ccm Dnepr motorcycle - it’s similar to old BMW motorcycles and has simple friction steering damper. Now I know what it is for 
Here’s the photo:
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Do you have link to the reddit thread? From the roadside advertisements it looks like it happened in Poland, and I do not think that car driver would receive citation here, but everything is possible. I wonder why motorcyclist was driving this way…
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It looks like the angle of the front forks, probably in combination with the weight distribution of the bike at the time, reduced the caster effect to the point where the normal negative feedback inherent in bike steering (the more you steer left or right, the more the bike wants to correct towards the direction of travel stabilising it, to positive feedback, where the bike steers more into turns and becomes unstable. This is a well known effect under heavy braking, where the suspension is compressed, the forks thus shorten and steepen in angle, and the bike becomes twitchier.caster
Reminds me of a tale I was told by a bike mechanic back in the day. This was a Vincent that crashed due to instability on a racetrack - the bike wasn’t badly damaged but the rider was killed. The bike was repaired but nobody wanted to ride it. It was checked over thoroughly and nothing was found to be wrong. Eventually somebody took it out, it started to wobble, he braked - the wobble worsened and, with great insight, he released the brakes and it came out of the wobble.
Anyone who knows Vincents well will probably guess what had happened.
Vincents had an unusual design of girder fork. On each side one of the joints had a cam so that the fork rake could be adjusted for sidecar or solo use. The forks had been set on sidecar by mistake. Under braking there was a loss of trail and the rest followed.
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Engineer here – yeah, my first thought was that it looked like the CG was too far back, causing instability. Operator trying to control with steering rather than shifting his own cg to compensate might have added PIO (pilot induced oscillation) in the roll axis as well. Once you get a two-axis interaction going, it’s not good.
Alternate possibility is too much free play on one of the axles. Broken bushing or …
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