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why if i hit hard the bar on the side without keeping it with my own hands on my 1500 all of a sudden it starts to wobble in a terrrible way then it rapidly gets worse to the point of going totally out of control like a sort of ghiroscopic effect??

then i grab the bar firmly and it stops and my ride continues smooth like nothing ever happened....

i always wondered why all this...and each 1500 i did this test.....all the same!
 

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Someone wrote a pretty good explanation of that once, I would not even know how to begin to search for it. If I remember correctly it is something like this, made sense to me. The wobble is actually the tire bouncing off the road to one side then the other and causing the steering to turn to the opposite direction of the last bounce giving it that wobbling feeling. That goes right along with my theory of heavier fork oil (more damping) fixing the wobble.
 

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The dreaded steering wobble, or shake. It has a lot to do with the geometry of the front end of the motorcycle. Lots of bikes experience it. Some old models even went as far as to incorporate a steering dampener shock. I've seen them on some older small bikes. Goldwings seem to be prone to it under certain conditions. Probably because it's a heavy bike, so it puts more weight on the steering head.

Most people that experience it, complain of it while decelerating between 35 mph and 25 mph. Especially if they take both hands off the handlebars at the same time. Almost always, if at least one hand is on the handle bars, it dampens the steering enough that you won't get a wobble. But on one occasion I experienced a force strong enough that required both hands to stop it. (I was run off the road and I jumped a curb going back on the road.)

There are lots of opinions as to what causes it, but it has to do with the self righting forces of the motorcycle (hence the geometry). When something pushes the wheel off center, the bike wants to re-center itself and the wheel goes back to center, but it over corrects and then it's pointing to the other side. So it re-centers itself but over corrects again. It sets up an oscillation and the wheel goes back and forth. Depending on the conditions, the oscillation can grow worse with each swing of the wheel, that is unless another force is there to dampen it. Without something to dampen it, you get the tank slapper. If nothing else is there to stop it, your hands are your last defense. So when you take both hands off the handle bars, all it takes is a small bump and away it goes.

The first time it happened to me, it scared the daylights out of me. I wasn't ready for it and I thought the bike had a major mechanical problem. I talked to an experienced friend at the Honda shop. I was embarrased to admit that I was riding no handed. She laughed and told me to keep my hands on the handle bars. Then she explained that actually it's a common thing and many many people had told the same story before me.

Several things are known to affect it.

First check your tires. Tires that are abnormally worn, or out of balance are more likely to set up the wobble conditions. It doesn't happen as often with new tires. But you shouldn't have to replace your tires early just to stop the wobble. The tires don't cause the problem, they just set up that bump that is needed to start the shake. And the worse the tires, the more often you will feel it.

Because of my own experience, I am a big believer in the importance of the adjustment of the steering head bearings. It's probably the best thing you can do for the situation. I'm not saying loose steering head bearings cause the problem, and I'm not saying tight steering head bearings solve the problem. But I am saying that it makes a big difference. If they are too loose, it's just that much easier for the wheel to swing back and forth. If the steering head bearings are well adjusted, they will offer some dampening to the steering, and help overcome the bikes tendency toward the steering wobble.

My personal experience with my 1200 was that it wobbled rather easily. I just learned to live with it. I didn't know much about it at the time. After a couple years, when the bearings wore out, I knew they needed to be replaced because I could feel a "notch" in the steering, so I replaced them. I did it myself, and I muddled my way through the job. I didn't know how to properly torque them so I did it by trial and error. It took three tries. The first time they were too tight, and the bike tended to wander as the steering was too slow to return to center. So I loosened them up and then it wanted to wobble really easily. So I tightened them a little bit and I think I got them pretty well right. The bike felt really good, and I didn't experience a steering wobble again for about 2 years. That notch I felt means the bearings are shot. They will be loose long before they are worn out. Maybe by a few years. So if your front end is loose, that doesn't mean you need to replace your bearings. It could just be time to tighten them up a little bit.

If you want to test it, get out on a side road where there isn't any traffic at all. Go about 25-30 mph. Take both hands off the handle bars and then lightly slap one of the hand grips. If it starts to wobble and the wobble grows quickly, it's time to make some adjustments. If it's really loose, it will wobble really bad, really quickly so be ready to grab the bars. Intentionally inducing a shake isn't exactly one of the safer road test items you can do, so be careful. Be ready to grab your handlebars quickly with both hands.

Somebody posted an article here once, a really good write up about how to tighten them correctly to ensure the bearings reseat properly. I saved the link for just such an occasion:

http://www.motorcycleproject.com/motorcycle/text/shucking.html
 

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Wolfman, that is a very clear explanation; a light just went on.I think I can see why it usually happens when decelerating:

First, since the faster you travel on two wheels, themore powerfulthe force of gyroscopic motion; thisis why it's easier to take your hands off the bars at higher speeds.

So if the first correction the bike makes starts at say, X mph, because you are decelerating, by the time the tire gets to the straight forward position, you are going slower -- X-1.Sothe required force to correct the bike at that point is less than it was originally, and the correction amounts to overkill. So it's easy to understand why it turns into a tank slapper.

Is this correct? If not, please straighten me out. Thanks.
 

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Bob Cassel
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I may be way off base here, but I also recall that the effect is initiated or intensified by the geometry of where the wheel contacts the road being out of line with the line from the steering head, through the forks and through the center of the front wheel. Kind of like the crazy wheel syndrome on shopping carts. The contact with the ground is behind the line of the turning stem.

I'm not sure I understand the concept enough to describe it, but when I read it it made me say, "Okay"
 

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PAPete wrote:
Wolfman, that is a very clear explanation; a light just went on.I think I can see why it usually happens when decelerating:

First, since the faster you travel on two wheels, themore powerfulthe force of gyroscopic motion; thisis why it's easier to take your hands off the bars at higher speeds.

So if the first correction the bike makes starts at say, X mph, because you are decelerating, by the time the tire gets to the straight forward position, you are going slower -- X-1.Sothe required force to correct the bike at that point is less than it was originally, and the correction amounts to overkill. So it's easy to understand why it turns into a tank slapper.

Is this correct? If not, please straighten me out. Thanks.
I never thought about that, but it makes perfect sense to me. I think you may have drawn a good conclusion.
 

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bcassel wrote:
I may be way off base here, but I also recall that the effect is initiated or intensified by the geometry of where the wheel contacts the road being out of line with the line from the steering head, through the forks and through the center of the front wheel. Kind of like the crazy wheel syndrome on shopping carts. The contact with the ground is behind the line of the turning stem.

I'm not sure I understand the concept enough to describe it, but when I read it it made me say, "Okay"
No, actually you are on the right track. It sounds to me that you are getting into the head angle, rake and trail, and thisis allabout the steering geometry. And these dimensions are a big part of what cause the self righting action ofbicycle and motorcycle steering.
 

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there are lots of explanations, but i kinda do not believe on them, i just wonder what would happen if you had a goldwing engine hanging freely and turn it on, i guess it would somehow move side to side being a boxer engine having the pistons moving side to side.

i have not heard any complain of wobling steering from any harley or metric v-twins cruisers or in line engines. i have heard complains from a close friend of feeling the same wooble on his boxer bmw.
 

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William_86 wrote:
i have not heard any complain of wobling steering from any harley or metric v-twins cruisers or in line engines. i have heard complains from a close friend of feeling the same wooble on his boxer bmw.
The cruiser bikes have a greater rake and trail angle than a touring bike like a wing or BMW which causes them to be more stable but not turn as well. It has nothing to do with the engine configuration.
 

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DaveO430 wrote:
William_86 wrote:
i have not heard any complain of wobling steering from any harley or metric v-twins cruisers or in line engines. i have heard complains from a close friend of feeling the same wooble on his boxer bmw.
The cruiser bikes have a greater rake and trail angle than a touring bike like a wing or BMW which causes them to be more stable but not turn as well. It has nothing to do with the engine configuration.
That, and the pistons in the wing on one side are not all travelling the same direction at the same time so is counter balanced, hence its oinherent smoothness (one reason anyway). If I remember correctly, the old Yamaha 650 specials (My first bike actually) did have the pistons that did that and the vibration/shake was VERY noticeable at higher speeds.
 

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had a 77 haonda 750 with a 1100 big bore kit that would go like hell until you likfted off throttle then wobbled so hard it'd scare the skin off ya every time and that was an inline engine
 

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like what Dave say's. if the steering angle was strait up and down i'm sure the bike would tear your arms off.
so angling the forks out forward at the bottom. makes the bike track strait and true. unfortunately this makes it harder to turn for same reason. So every bike design is a compromise. you want a bike that can carve throw corners like a wing or one that can run down the strait away's like the cruisers and HD's
Wilf
 
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