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Old 01-05-2013, 10:53 AM   #1
wliggy OP
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1150GS Adv fork tube twisting?? Help please!

Good morning everyone!!!

I hope I am just overlooking something simple??? I am experiencing a very strange brake/steering issue!! When I panic brake very hard, it feels like the front wheel gets ripped out from under me!!! It pulls the front wheel to the right, I say pull, it feels more like it is sliding to the right!! It is a 2004 R1150 ADV with servo abs. As I watch this happen, I noticed it seems to be one of the front calipers grabbing! And as it does this, the left upper fork tube "spins"!! When I say spin, it literally twists 140-180 degrees!!! It is like (somehow) the torque from the brakes is "grabbing" the tube and twisting it!! Testing in the driveway, I have noticed when the brake grabs, it twists the tube and holds it until I release brake. When I let go, it twists back to original position.
My first thought was a brake pull, like a car would experience if a caliper was sticking. I realize that a motorcycle doesn't react the same as a four wheel machine, but that is where my brain went! So I removed calipers sanded barrels, made sure pads were good and everything is moving properly, and no change! Now I am thinking that something is loose in the front end "allowing" the brakes to jerk something!!! It is a very scary feeling! I loosened the front axle and pinch bolts, bounced the bike and retorqued front wheel while a friend was sitting on it. No change.
Then I started checking all the bolts on the front end. Even loosend the left fork tube at the top and re torqued it.

Any help would be appreciated!! I am definitely no professional mechanic, but I have been building jeeps for most of my life, and am ,comfortable in the garage! If anyone has any ideas, I'm all ears!!

Thanks
Willi
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Old 01-05-2013, 03:24 PM   #2
Mike Ryder
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WTF. That's weird. How are your spokes and or tire. I can't see how that tube could be made to spin as you describe. I'm not doubting you, just baffled.
sorry not much help.

Are these the original brake lines?
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Old 01-05-2013, 03:26 PM   #3
Zoef zoef
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Sir, do both tubes turn? Does the lower clamp rotate when compared to the upper? My first hunch would be that one caliper is not functioning. Temperatures of both disks should be more or less similar.
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Old 01-05-2013, 05:22 PM   #4
wliggy OP
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Scary

Thanks guys. I haven't checked spokes, but tires are new. The problem has been there for awhile, but I never smashed the brakes to get the "rip the front end out from under me effect". In the past, just manuvering in the driveway, I noticed that caliper "grabbing" and causing a strange twist effect in the front end, but never payed it any mind. I was new to the servo brakes, and thought it was a characteristic. But, last week I put new rubber on. I put the wheels on the bike and went around the block for a test ride. I was braking hard to seat everything. Then I would go back to the house and recheck all my torques. But, when my surprise issue popped up, I tore it all apart again and rechecked everything!!

I can manually spin both fork tubes with a bit of force by hand at a stand still. The top tube nuts are retorqued with loc tite.
When the issue happens, it is only the left tube torque-spinning!!! It is like something is letting the caliper lock that side up and really twist that left side!! It really does not make sense. I know that the fixed lower fork tubes are where the caliper would be applying the force, but it's like it is transferring through to the upper sliders somehow!

I have tried to search the Internet and do not see many similar instances. My closest BMW dealer is 2.5 hours away. I am friends with them and called for advise. They all said something has to be loose!! I just can't find it!!

Thanks again for any input!!

Willi
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Old 01-05-2013, 06:12 PM   #5
Mike Ryder
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It's normal to be able to rotate the tubes by hand when all nuts are torqued correctly.
This may sound odd but it is oddd. if only one calliper is applying force there is unequal loading on the tube bushings. perhaps you are able to create a sympathetic harmonic starting with the effected brake disk and transfer it
though the now laterally loaded bushing causing the tube to spin in, well, harmony.[?]
I know this sounds like an old StarTrec episode but thats all i got.

you may be on the verge on the flux capacitor technology!
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Old 01-05-2013, 06:34 PM   #6
slartidbartfast
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The left tube is bent.
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Old 01-05-2013, 07:22 PM   #7
Mike Ryder
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ya, or that.
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Old 01-05-2013, 08:36 PM   #8
BluByU
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Quote:
Originally Posted by slartidbartfast View Post
The left tube is bent.
Yep +1 on that

Take the tubes off the bike and spin them, bet one is bent. That or there is some major obstruction in the brake lines.
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Old 01-06-2013, 05:19 AM   #9
Steptoe
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Quote:
Originally Posted by slartidbartfast View Post
The left tube is bent.
Swop the tubes/stanchions over and see if the problem moves with the swop. Only a 5 minute job.
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Old 01-06-2013, 05:55 AM   #10
bemiiten
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Did you check the pinch bolts at the lower fork bridge? I doubt a brake caliper is causing the problem. Plenty of bikes out their with a single disk.
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Old 01-06-2013, 11:13 AM   #11
wliggy OP
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Bent

Thanks for the replies! I will pull the tubes and inspect.
When I hold the rear brake and compress the front end, it seems to slide freely with no twisting of the tube. Only twisting happens when caliper grabs. That's the only reason I did not think to check the tubes.

Not sure I can check it today, but I will let y'all know what I find.
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Old 01-06-2013, 11:19 AM   #12
wliggy OP
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Pinch bolts

And yes, I checked the pinch bolts just above the wheel on the fork bridge. They were only slightly under torque specs. But, after tightening,,,, no change.

I need a new dust seal on the suspect side tube anyways, it seems to weep a bit. So, ill pull the tubes out!
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