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BMW c650gt front wobble vibration

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Bojan Gjoshevski

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May 14, 2016
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Hey guys,
I have a front wobble on the handle bars from 35mph up.
I just installed new tires, balanced and the problem got worse. Very unstable on high speed 65-80mph
Shaking and wobbling is a bit pronounced and now I can even feel it on slower speed. When I release the handle bars the bike feels like it makes tiny eight’s.
Anyone have an idea what could be the problem?

Thanks,
Ben
 
I just tried going downhill, speed around 10mph, when I remove my hand from the handlebars the front wheel does turn right and then left. Like 8th as I mentioned.
 
P.s. when I got new tires fitted by a shop to my new-to-me K1600, the tech forgot (...) to tighten one of the front fork pinch bolts. As a result, the front axle had just a bit of play, which caused quite a vibration/shudder under braking. After I properly tightened that pinch bolt (the one that 'locks' the axle in place, by squeezing the bottom of the fork) the problem disappeared. So you may want to check that as well.
 
I don’t suspect a loose bolt because I already had the wobble. That’s why I installed new tires, I thought the front tire was the problem. Tires were installed in a BMW dealership so I doubt they would leave a loose bolt. I will try to play with the preload today and see if there is any improvement.
 
Adjusting the preload didn’t help. I tried again, on a slow speed around 10mph disengaged transmission, I release the handlebars and the motorcycle slowly goes on the left and then on the right. The handlebars are turning an inch to the left and then to the right. Any suggestions appreciated:)
For now i think the tires are properly inflated 37-42, brand new and balanced.
I didn’t mention the the bike has 8500 miles from 2020.
 
This may be out in left field. If the tire is securely mounted put the bike on the center stand and first check for play in the wheel bearing although that should have been checked when the tire was mounted. If the wheel bearings are good then have someone sit on the bike to weigh it down and try wiggling the forks to see if the forks or the triple tree bearings are loose. On my first scooter (not BMW) the triple tree to frame mounting bolt had worked itself a little loose and my handlebar was wiggling all over the place. If all of those are tight check the rear tire mounting and rear axle bearings. Those are the only things I can think of that could cause the symptoms you have described. Whether the above is the cause or not please keep us posted on what you find out.
 
mjnorris said:
This may be out in left field. If the tire is securely mounted put the bike on the center stand and first check for play in the wheel bearing although that should have been checked when the tire was mounted. If the wheel bearings are good then have someone sit on the bike to weigh it down and try wiggling the forks to see if the forks or the triple tree bearings are loose. On my first scooter (not BMW) the triple tree to frame mounting bolt had worked itself a little loose and my handlebar was wiggling all over the place. If all of those are tight check the rear tire mounting and rear axle bearings. Those are the only things I can think of that could cause the symptoms you have described. Whether the above is the cause or not please keep us posted on what you find out.
Click to expand...
Thanks Mjnorris,
I’ll definitely update when I find out what’s the issue. I don’t believe it’s the rear because it would probably pull on one side or the other.
I’ll have to go to the dealership and have them inspect the bolts on the handlebars head.

Ben
 
Use a workshop stand to lift the front wheel by the fork. Spin the wheel in a vacuum and see how it performs! Don't ride like this.

The fact that vibration and movement disappear when you brake (i.e. when the load on the front wheel increases) is a clear indication that you have wobbling.

Can be caused by :
- a warped rim (front or rear),
- an unbalanced wheel (front or rear),
- tire wear or tire mounted incorrectly or upside down (front or rear),
- abnormal play in wheel bearings (front) or axle bearings (rear),
- poor suspension condition (front or rear).
- a top case located far back and loaded,
- inadequate tire pressure (front or rear),
- improper centering of the rear wheel.

A simple visual check will usually reveal the cause of the Shimmy.
 
Last edited:
Kiss4u said:
Use a workshop stand to lift the front wheel by the fork. Spin the wheel in a vacuum and see how it performs! Don't ride like this.

The fact that vibration and movement disappear when you brake (i.e. when the load on the front wheel increases) is a clear indication that you have wobbling.

Can be caused by :
- a warped rim (front or rear),
- an unbalanced wheel (front or rear),
- tire wear or tire mounted incorrectly or upside down (front or rear),
- abnormal play in wheel bearings (front) or axle bearings (rear),
- poor suspension condition (front or rear).
- a top case located far back and loaded,
- inadequate tire pressure (front or rear),
- improper centering of the rear wheel.

A simple visual check will usually reveal the cause of the Shimmy.
Click to expand...
Thank you, next week I’ll go to the dealership and try to find out what’s happening. I don’t suspect on the suspension as the bike has 8k miles and everything feels nice and smooth. It could be a rim or some torque problem in the front. I’ll keep you posted. It’s weird no one had this problem on the forum:)
 
Is there any way I can upload a short video here?
I just lifted the bike on the center stand and recorded a video from the rear tire. Its oscillating left to right a bit. Maybe that’s normal because it’s spinning free but wanted to post the video and get your thoughts.
I tried moving the wheel left and right and it’s nice and stable, that means the bearing should be fine. Also the front one is very stable.
I don’t have a lift so I can spin the front wheel and see if it’s oscillating.
 
Bojan Gjoshevski said:
Is there any way I can upload a short video here?
I just lifted the bike on the center stand and recorded a video from the rear tire. Its oscillating left to right a bit. Maybe that’s normal because it’s spinning free but wanted to post the video and get your thoughts.
I tried moving the wheel left and right and it’s nice and stable, that means the bearing should be fine. Also the front one is very stable.
I don’t have a lift so I can spin the front wheel and see if it’s oscillating.
Click to expand...
Just for future reference, there's another way to show videos:

1) Post it on YouTube (or Vimeo, or some other video site -- but YouTube is free, if you have a free Google or gmail, etc., account).

2) Just paste the YouTube, etc., link -- URL -- in a post here.

For instance, I did that -- posted the YT links -- with this post, and you can see how it comes out:

wspollack

Thread 'C 400 GT: Speedometer Accuracy Test'

I've done a few top-speed tests on the C 400 GT, such as this one showing the tach that I made awhile ago ...


... and I made a speedometer accuracy test on my other bike, a Royal Enfield Meteor 350, last year ...


... but I hadn't done the speedometer test on the C 400 GT until a few days ago. I just finished the video on that:


If you're interested, the details on my methodology are in the full description of that video: click the MORE link when viewing it on YouTube.

The executive summary, according to me, is that the speedometer...
  • Like

This method is the typical way that members show a video on pretty much all Internet forums, although your DropBox method certainly works, too (I just viewed it, but I got nuthin').
 
Last edited:
Just an update.
I went to the BMW service today. The technician rode the bike and did replicate the wobble. He said that head bearing wouldn’t wobble like that, it would be a different wobble. They checked front tire and even did dynamic balancing. Everything else, forks, wheel alignment was checked and no problems. The wobble is a little better but it’s still there around 40mph. Also when i ride slow around 10-20mph I feel like the road is bumpy, the technician didn’t notice that. Their conclusion was that probably the tires are bad even though they are brand new. I will contact Michelin and see if i can get a new pair. I’m still suspicious because I had the wobble with the old tires too, that’s why I replaced them.
Ben
 
I was just checking the tire beads and noticed that they are a bit off on both tires. Could that be the problem? This are photos of the rear tire. I’ll post a video where you can see the play.
 

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