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Old 11-08-2018, 11:21 AM   #21
JTS
 
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Re: Death wobble video

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Originally Posted by Jarrett View Post
Just out of curiosity, what size guy is your friend?
I would say he is 6 footish, 210. In decent shape, no beer belly or anything.
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Old 11-08-2018, 11:27 AM   #22
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Re: Death wobble video

Hope he heals fast. Thanks for the info.
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Old 11-08-2018, 11:56 AM   #23
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Re: Death wobble video

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.
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Old 11-08-2018, 01:30 PM   #24
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Re: Death wobble video

Glad your friend is OK.

The first comment on that YouTube video had me rolling,
"i was holding onto my mouse for dear life"
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Old 11-08-2018, 05:13 PM   #25
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Re: Death wobble video

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.

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.

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.

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.

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!

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.

I had one high speed wobble on my KLR and all that saved me there was the hand of God... I kid you not 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.
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Old 11-08-2018, 05:16 PM   #26
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Re: Death wobble video

Quote:
Originally Posted by tshelfer View Post
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.
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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The number one rule for this forum!
Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen. Eph 4:29 (NIV)
Think before you post. Leave out the vulgarity, personal attacks and foul language!

Quote:
"However lofty the goals, if the means be depraved, the result must reflect that depravity." - Leonard E. Read

Lies are fragile. They require constant attentiveness to keep them alive. The exposure of a single truth can rip through an ocean of lies, evaporating it instantly. - Brandon Smith

If you want government to intervene domestically, you’re a liberal. If you want government to intervene overseas, you’re a conservative. If you want government to intervene everywhere, you’re a moderate. If you don’t want government to intervene anywhere, you’re an extremist. — Joe Sobran

It is no crime to be ignorant of economics, which is, after all, a specialized discipline and one that most people consider to be a ‘dismal science.' But it is totally irresponsible to have a loud and vociferous opinion on economic subjects while remaining in this state of ignorance. – Murray N. Rothbard

When one possessed of the Truth suffers from a heavy heart he is susceptible to a more dangerous affliction — the craving for power to eradicate error, to cause Truth to triumph by force. - Frank Chodorov

Where politicians flourish, long history has harshly taught us, people and their liberty wither. Where the state is god and the "public interest" worshipped, individual man will be found bleeding upon the altar. - Karl Hess

The accepted wisdom is that without the state, society would collapse into lawlessness and crime. In fact, lawlessness and crime define the very nature of the state and the society organized by it. - Bionic Mosquito

But the myth of the rule of law does more than render the people submissive to state authority; it also turns them into the state's accomplices in the exercise of its power. For people who would ordinarily consider it a great evil to deprive individuals of their rights or oppress politically powerless minority groups will respond with patriotic fervor when these same actions are described as upholding the rule of law. - John Hasnas
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Old 11-08-2018, 07:16 PM   #27
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Re: Death wobble video

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.
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Old 11-08-2018, 07:42 PM   #28
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Re: Death wobble video

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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Old 11-09-2018, 02:56 PM   #29
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Re: Death wobble video

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. 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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