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Death wobble video

JTS

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A while back there was a video of someone testing on a track. The rider would put the motorcycle in a tank slapper/death wobble and recover by lowering his center of gravity by laying on the tank.

I am trying to find the video but haven't been having any luck. Does anyone remember the thread it was posted in?

A friend of mine just crashed his loaded bike heading to the hill country 500 and he said the front end just felt light and started weaving before he went down at around 60-70 mph.
 

Jarrett

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Yeah, hope he is ok. What bike was it?

Is this the video?

[ame="https://www.youtube.com/watch?v=GvHtChodNk0"]TANKSLAPPER! MAM 6/28/10 - YouTube[/ame]
 
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JTS

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He is going to be ok, some broken fingers, wrist, ankle, some road rash. It happened on the 3rd and he is in Parkland now. He was riding a 2018 KTM 1290R. He had it loaded down pretty heavy for some camping.


I remember the video being pretty old. From like the 60's or 70's.
 
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Language warning on Jarret's video.

Even worse is what that video did to my shorts. Holy smokes that was scary. That guy didn't pull over because he rode through some mud, he needed to catch his breath and change his shorts.

I've had one tank slapper and it's no fun. Glad your friend is ok.
 
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He is going to be ok, some broken fingers, wrist, ankle, some road rash. It happened on the 3rd and he is in Parkland now. He was riding a 2018 KTM 1290R. He had it loaded down pretty heavy for some camping.


I remember the video being pretty old. From like the 60's or 70's.
[ame="https://www.youtube.com/watch?v=fvsDIq3WwVA"]https://www.youtube.com/watch?v=fvsDIq3WwVA[/ame]

Wobbles and Weaves part starts at 4:00
 
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Jarrett

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He is going to be ok, some broken fingers, wrist, ankle, some road rash. It happened on the 3rd and he is in Parkland now. He was riding a 2018 KTM 1290R. He had it loaded down pretty heavy for some camping.
****, that's scary. Didn't know loading one down could cause issues like that.
 

South Tex

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Glad to hear he’s gonna be ok. Not to change the thread, but maybe we could get a ride/crash report? What gear was he wearing and did it work or fail. Real life experience is how we really learn.


Sent from my iPhone using Tapatalk
 

JTS

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I haven’t asked much of the details of the crash or the gear other than how fast he was going. I will get more details after he is released from the hospital.
 
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Cant be too pretty, wobbles at 60-70mph would be violent.
Glad he is relatively okay.
it's been said a bunch on the recent crash/surgery threads, make sure to stress to him about following PT.

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Jarrett

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In general though, is this a thing?

Loaded down bike developing a wobble due to additional weight?
 

Tuco

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Glad your friend escaped major injury. Hopefully no long term effects.

The British video was enlightening. I've not experienced wobble or weave; it looks scary.
 

JTS

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In general though, is this a thing?

Loaded down bike developing a wobble due to additional weight?
Looking at the video, it doesn't appear that the additional weight would be the issue. Maybe the top rear box or the panniers may cause some issues.
 
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In general though, is this a thing?

Loaded down bike developing a wobble due to additional weight?
It is not the loaded down part, but more importantly the weight distribution. Typically, loading gear on a bike is done high and to the rear. This is inherently bad as demonstrated in the video where shifting weight forward and lower calms the wobble.

But I do have a hard time resolving how adding a pillion is good compared to loading gear. I suppose the weight distribution of a person is not all up high since the legs are about 30% of the body's mass.
 
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bwdmax

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In general though, is this a thing?

Loaded down bike developing a wobble due to additional weight?
The short answer…..
This is definitely a possibility. Suspension is an important part of a motorcycles handling. The springs are designed to carry or hold a certain amount of weight. The pre-load adjustments are to compensate within a range of weight that a spring can work. When pre-load is adjusted at either end of the bike usually the rear you also change the rake and trail (the angle and relation of the fork to frame) this affects how quick of slow the bike steers. There are other factors with springs such as bottoming or topping out the suspension. When the suspension bottoms out you suddenly load the tire that now acts as a spring of unknown characteristics depending on air pressure, temperature, speed, available traction ect. When you top out the suspension you abruptly unload the tire and remove contact from the tire. In the event that you overload the rear you can simultaneously bottom out the rear and top out the front causing a wobble or other undesirable effect.
Most modern adventure and touring bikes have hydraulic preload adjusters on the rear to allow for quick easy adjustment within the range of the spring. This allows you to add or remove luggage or passenger and retain similar handling with the range of your particular spring. The handling on my Strom is greatly affected by this.
 

Jarrett

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Looking at the video, it doesn't appear that the additional weight would be the issue. Maybe the top rear box or the panniers may cause some issues.
Just out of curiosity, what size guy is your friend?
 
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I can feel a difference when my VStrom is loaded with 50 or 60 lbs of camping gear. But honestly, the only time I'm really aware is on extremely low speed corners.

I used to have a '79 Honda CB650 (sold it about 10-11 years ago). That bike tended to develop an unnerving front end shimmy about above 65 mph after I took the original Vetter-style fairing off. Who would have thought the weight of a fairing would have made such a negative impact.
 

Tourmeister

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:tab Under normal conditions, the bike WANTS to be stable. Normal conditions are both wheels on the ground with good contact patch and a bit of rake angle on the front forks. IF the bike encounters something in the road like a surface irregularity or something on the surface of the road, the front end might deflect. Again, under NORMAL conditions, the bike will self correct and any kind of wobble will normally damp out.

:tab Adding weight to the back of the bike affects the rake angle on the front of the bike. Normally, you would associate the greater rake with more stability, like say on a cruiser. However, cruisers are still balanced front to back so that the front end still has the correct weight on the tire to maintain the desired contact patch size. Simply adding weight is not going to cause wobbles, especially if the rear suspension sag is adjusted. Where the weight is added is what matters most. Adding weight BEHIND the rear axle lightens the front end. So even though you are increasing the rake, the lack of contact patch size becomes more of an issue, reducing the bike's normal ability self correct.

:tab When you have a bike loaded with luggage that is high and rearward, you are lowering the inherent stability of the bike. Adjusting the rear suspension to maintain proper sag helps. Add too much weight behind the axle and adjusting your rear sag will not overcome the problem. The bike might seem fine in a straight line on a relatively smooth surface, but it will be much more sensitive to disruptions because its normal ability to self correct has been reduced. IF the rider is paying attention, the bike might feel a little more "nervous", which is a good indicator that you need to make a change! If the rider does not, then something as simple as an undulation in the road surface or even getting on the gas too hard in a curve can upset the bike and induce a wobble. Rider reaction can make it better or worse. Most people will instinctively react by either chopping the throttle, hitting the brakes, or both. THAT can cause a crash even when the wobble might have damped out had none of that happened. The reactions CAUSE a wobble to become a tank slapper.

:tab The accepted means of correcting a wobble is to get weight on the front tire WITHOUT making sudden speed changes or sudden braking inputs. This is the reason for the advice to lay on the gas tank and get your weight forward. This increases the contact patch and restores the normal tendency of the bike to self correct, hopefully in time to prevent a crash.

:tab Tire pressures, head bearings, and suspension settings can all affect the handling of the bike and contribute to wobbles. However, from what I have experienced and learned from reading about it, weight distribution is the biggest culprit, unless you have something REALLY extreme regarding the condition of the tires, bearings, and suspension. Those riders you see with MASSIVE piles of luggage on the back of their bikes are taking a BIG risk!

:tab I have ridden with passengers and/or luggage and experienced the front end getting uncomfortably light. On hard acceleration, from a stop or out of a corner, there have been times where the front end came up and when it came back down, I got a wobble. In every case, I was able to ride through it because I didn't panic and make a sudden input to the bike. In most cases, doing NOTHING actually allowed the problem to self correct. In a few cases, I pulled myself forward to get more weight on the front end and that took care of the problem. Once I was aware of the issue, If I could not stop to correct it, I simply had to change my riding to be much more aware of the difference in handling.

:tab I had one high speed wobble on my KLR and all that saved me there was the hand of God... I kid you not :shock: I later figured out that causes were VERY loose head bearings, VERY soft springs in the front (which actually reduced the rake), and the nasty buffeting of an 18 wheeler I was approaching from behind. I truly thought I was going down and was already looking into the grass median to see if there was anything I'd hit once I parted from the bike. Then... just like that...it stopped... I had been gradually rolling off the gas and was shifting my weight back in anticipation of trying to jump clear of the bike as it went down. I had unwittingly reacted appropriately. Once home, I corrected the suspension/bearing issues and the bike never had a problem again.
 

Tourmeister

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I used to have a '79 Honda CB650 (sold it about 10-11 years ago). That bike tended to develop an unnerving front end shimmy about above 65 mph after I took the original Vetter-style fairing off. Who would have thought the weight of a fairing would have made such a negative impact.
:tab It might have been an aerodynamic issue more than a weight issue. For instance, KLR front fenders pre '08 were notorious for flopping about once you started getting up over 65 mph. This could cause the front end to get real wobbly feeling. A common solution was replacing them with KTM fenders that were more rigid.
 
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That could be. My solution was to sell the Honda - which was a beater I bought just to ease back into riding - and buy my first VStrom. My solution was definitely fun.
 

JQ1.0

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Experienced what I referred to as a high speed wobble ( video refers to it as a weave ) many years ago on a SP370 at about 90 indicated. It was all I could do to keep it in a single lane. Off the gas it only lasted a few seconds but the memory has lasted a long time. Those of you that know what a SP370 is can estimate how long ago that was when I say the bike was only a couple years old. To the best of my recollection tires stock and in decent shape. High speed on a 370 is code for down hill and tucked with a tail wind.
 
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May 2017 I had a tankslapper at around 70-80mph on a Buell Ulysses. I remember trying to throttle out of it. Apparently that was the wrong move. :doh: Anyways I went down with broken clavicle, 9 broken, ribs, punctured lung, and a hemothorax. I think the cause was me not having the right amount of oil in the forks when I changed it a few days before. It had been lowered by the previous owner and with the bike already having such a tight rake and short wheelbase it really messed it up with I gassed it to go around a car on the highway. All of my sport bikes in the past had dampers, not this one, unfortunately.
 
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