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Old 07-18-2010, 07:25 AM   #16
Boon Booni
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Quote:
Originally Posted by Ducksbane
Geno_Rocket ... I think you should check your rear ride height ....

That's a good point. The OP said nothing about verifying correct sag for the suspension. Sag is the first place I'd look then if it keeps weaving I'd lower raise the forks in the triple tree 5mm and see if that makes a difference.
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Old 07-19-2010, 06:03 PM   #17
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Quote:
Originally Posted by Ducksbane
Geno_Rocket ... I think you should check your rear ride height ... Much as I dislike the front K60 on loose surfaces I have Never had any instabilty on a firm surface.
I would be concerned and check the ride height if the wobble occured anywhere else except this spot on the interstate. That mixture of rain grooved asphalt and concrete is the only place where I have the issue, but it is a big issue there, so I am chalking it up to the tires. When I get away from this one stretch of highway (I-64 east and west at the I-270 interchange in STL for anyone so interested) then I have no problems. Just a perfect mixture of traffic speed, wheel diameter, tire tread, and suspension mass to make the bike squirrely on those grooves.

Heck, the rain grooves on the highway at that location would probably be considered ruts in some locations. Now that I think about it, that is why I took the BMW adventure riding school - to learn how to ride those things!

Ducksbane, as you suggest, rear ride height should not be overlooked. I read back through the posts and none of the original posters mentioned whether the wobbles occur when the bike is fully loaded or not. Assuming the rear ride height is at the lower limit of specifications, and the front is at the upper limit and you are riding the bike fully loaded with gear - the net result can be a significant unloading of the front end and resulting instability at speed. I have the preload cranked up pretty high as I am a big boy, so I discounted that point in my situation. All that said, this weekend, when riding over my favorite highway interchange with fully loaded bags, I felt there was a bit more wobble, but I knew why and expected it - the load I was carrying unweighted the front end a bit more.

Okay, at the risk of extending this thread even more, does anyone know how much difference the diameter of knobbies (any type) are from the OEM tire? That difference in diameter could upset the ride height and potentially bring on a wobble. Now a F8 is not a racebike, but racers are concerned with such things. What the heck, the post is only two pages long right now.....

geno_rocket screwed with this post 07-19-2010 at 07:07 PM
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Old 07-19-2010, 08:36 PM   #18
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Wobble continued

Thanks for all the comments, they have certainly got me testi g different theories.... I have experimented since my original post and I am absolutely convinced of a couple things, first of all the wind can be a significant factor in wobble, as u are buffeted back and forth...that in combination of a death grip when it happens only exacerbates the problem.

Have gotten to a point where I can duplicate the wobble every time, and while the knobbies make the problem worse, I think wind buffet and loose clothing combined with gripping too hard plays an equal part.

I can almost always decrease the wobble down to almost nill with some simple adjustments.....

May not work for everyone but in my case it sure did.

Thanks all
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Old 07-20-2010, 03:33 AM   #19
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I put my stock Anakee's back on to compare....Let's just say the wobble(Squirrelliness) has gone away and all I can say is 180KPH is no problem and stable!
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Old 07-20-2010, 04:42 AM   #20
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Quote:
Originally Posted by GrizGirl
I was just writing up some thoughts on the 800 after going 4700 miles over every imaginable road surface in 9 days of driving. The front end with knobbies and highway driving became an issue on the trip. It is unstable. Above 90 mph it is downright dangerous. Yes, at highway speeds with knobbies you will feel the frontend wobble. I felt it with the battlewings as well but it was not as pronounced as when I went to TKC-80's.

Up to 85 I just had to get used to the wobble. It never affected cornering or my ability to maintain control of the bike. You start going faster than that and you have some issues. Just be aware and watch your speed, particularly when you are passing at interstate speeds. More details will be in a post I'm working on.

Cathy

21 inch front wheel, Knobby tires and 80+mph on pavement, and people think the front end shouldn't wobble?
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Old 07-21-2010, 01:43 PM   #21
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Running the stock battlewings, no wobble, to 95 MPH. I put on TKCs for some off-roading in Colorado, and experienced the same wobble above 75mph with a single rider. Adding the wife on back, and the wobble range increased to ~85 mph, so extra weight on the bike definitely makes a difference. The wobble lessened some after 1000 miles or so on the TKC80s (all on about 4 days) That may have had something to do with rubbing the corners off the knobs.

Justa noob view.
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Old 08-19-2010, 12:12 PM   #22
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Quote:
Originally Posted by Moab
Thanks for all the comments, they have certainly got me testi g different theories.... I have experimented since my original post and I am absolutely convinced of a couple things, first of all the wind can be a significant factor in wobble, as u are buffeted back and forth...that in combination of a death grip when it happens only exacerbates the problem.

Have gotten to a point where I can duplicate the wobble every time, and while the knobbies make the problem worse, I think wind buffet and loose clothing combined with gripping too hard plays an equal part.

I can almost always decrease the wobble down to almost nill with some simple adjustments.....

May not work for everyone but in my case it sure did.

Thanks all
I am getting the same speed wobbles after switching to TKC80's. Did BMW of Utah swap out your rubber? They swapped out mine! I wonder if they dont balance them after they swap? Did you end up pulling the weights off of the front wheel? PM'ed



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Old 08-19-2010, 01:36 PM   #23
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Quote:
Originally Posted by MSH
I am getting the same speed wobbles after switching to TKC80's. Did BMW of Utah swap out your rubber? They swapped out mine! I wonder if they dont balance them after they swap? Did you end up pulling the weights off of the front wheel? PM'ed



Matt
I threw a set of TKC on my bike and forgot to balance them. They had a pretty noticeable hop at around 35-40 mph, but on the highway they were smooth up to about 80. Never got above that, and no wobble for me.

They were 1.5 ounces out of balance when I checked.
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Old 08-19-2010, 02:50 PM   #24
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I could feel how the front end became less stable when putting on a metzeler karoo 2 (without the T). Nothing huge just more nervous so to say.

Increased pressure to 2.2 bar and since then I dont notice as much.

What I am experiencing is exactly what I expected when I switched from my r1200gs with wider and smaller front wheel to this proper narrower and larger wheel of the f800gs.


I guess that every thing you do to make the bike handle better offroad will cause it to handle worse onroad...
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Old 08-19-2010, 07:49 PM   #25
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Quote:
Originally Posted by ecce
Increased pressure to 2.2 bar and since then I dont notice as much.

I guess that every thing you do to make the bike handle better offroad will cause it to handle worse onroad...
What is 2.2 bar? A European measurement?

True!
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Old 08-19-2010, 07:59 PM   #26
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Quote:
Originally Posted by MSH
What is 2.2 bar? A European measurement?

True!

32(ish) PSI
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Old 08-19-2010, 08:17 PM   #27
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Quote:
Originally Posted by upweekis
21 inch front wheel, Knobby tires and 80+mph on pavement, and people think the front end shouldn't wobble?
Hmmm... at what point did I say I expected a smooth ride? I didn't. There will be a wobble, there will be movement in the front, even at much slower speeds. What shouldn't happen are death defying full bike sways from left to right that had my companion convinced I was going to die that day. That shouldn't happen.

And no, I was not overloaded, me and my gear weighed less than many of the riders alone weigh who have 800's, so that was not the problem.
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Old 08-19-2010, 09:11 PM   #28
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Quote:
Originally Posted by MSH
What is 2.2 bar? A European measurement?

True!
The standard conversion is 14.5 PSI= 1 bar
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Old 08-20-2010, 01:01 AM   #29
Ceri JC
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Things I'd check:
Tyre pressure,
Wheel bearings,
Headstock bearings,
If all those are okay, try street tires and balance the wheels for the street tyres.

Only problem I've had in this area was my bike liked tracking straight a bit too much, turned out to be headstock bearings (replaced under warranty).
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Old 08-20-2010, 05:04 AM   #30
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Gaaahhh!!! It just sucks to be doing investigative repair work on a bike that has 700 miles. I know its the rubber knobbies. The first 600 miles were free of any kind of problem. No wobbles, nothing!

Has anyone tried a front tire (knobby) that didnt shimmy and shake?
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