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Old 08-07-2012, 12:30 PM   #1
cobrakai OP
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High Speed Wobble

Getting some handlebar wobble around 70mph and above, more noticeable under power, on smooth straight asphalt. I understand I need to increase Rake/Trail. To do this, I should:

Increase rear sag (lower ride height)
Decrease front sag (raise ride height)
Lower forks in clamps (raise ride height)
Increase tire pressure in the...?
Change damping?
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Old 08-07-2012, 12:48 PM   #2
JimVonBaden
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Make, model, year of bike? Yes, it matters.

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Old 08-07-2012, 01:33 PM   #3
the_gr8t_waldo
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before messing with the bikes geometry, first check the wheel bearings...both front n back.................................. fact is, while the front is proped up, check the steering head bearings as well.

the_gr8t_waldo screwed with this post 08-07-2012 at 01:40 PM
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Old 08-07-2012, 02:01 PM   #4
cobrakai OP
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2007 BMW G650 Xmoto

I checked the steering bearings and they feel solid. No wiggle noticeable. The bike's only got 7000 miles all on the street, feels real solid still.
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Old 08-07-2012, 02:36 PM   #5
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Front wheel balanced? Rimlocks?
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Old 08-07-2012, 03:33 PM   #6
GreaseMonkey
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Did the wobble just start happening? If so, then something has changed and you need to find out what it is and then you can start figuring out how to fix the wobble.
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Old 08-07-2012, 03:48 PM   #7
GH41
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Quote:
Originally Posted by cobrakai View Post
2007 BMW G650 Xmoto

I checked the steering bearings and they feel solid. No wiggle noticeable. The bike's only got 7000 miles all on the street, feels real solid still.
I'll bet the head bearing is the problem. To do a wiggle check the front end has to be off of the ground and the handle bar centered. If you have the dvd and tools just adjust it. The hardest part is getting the bike off of the ground. Why would you change the rake by moving the tubes up and down? Give BMW some credit for designing the damn thing. GH
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Old 08-07-2012, 04:48 PM   #8
cobrakai OP
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No, it's not a new thing. I have noticed it less with the addition of more tire pressure, up from the stock 26f/29r to 32f/35r, but it's still there. I can induce the wobble by rocking the bars side to side. It doesn't get much worse, but it requires my constant feedback to keep it stable.

I did in fact lift the front of the bike using a stand, loosened the upper triple clamp, and torqued the bearing per the service manual. There is no slop there. The wheels have been balanced somewhat recently using static balancing.
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Old 08-07-2012, 05:04 PM   #9
GreaseMonkey
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Did you do anything like install panniers, or change the seat or handlebars? Does it ever go away, or is it always there?
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Old 08-07-2012, 06:17 PM   #10
Switchblade315
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new /old tires. bent rim?
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Old 08-07-2012, 06:19 PM   #11
cobrakai OP
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No gear or extra weight on the bike at all. It's always been like this, I'm just now trying to figure it out.

This is not a dangerous tank slapper of any kind, it feels more like a wobble or general uneasy feeling. Other motorcycles I've ridden are very solid.
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Old 08-07-2012, 06:24 PM   #12
GreaseMonkey
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Is the tire size the same as recommended? Might as well start there. You can put the bike up on the center stand and spin the tire to verify there is no physical defect. Sometimes you can use a screwdriver to pry the front pad away and move the caliper so it does not rub, and have it be friction free enough you can do a gravity balance check on the wheel.

And just so all the bases are covered, check the back tire for any wobble including swing arm play.

That should, keep you busy for 4 or 5 minutes.
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Old 08-07-2012, 06:33 PM   #13
drmajor
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Wobble

Check your tires... Run your hand over the tire. Does it have high/lows....ie, cupping or feathering.??

Had this on my LT. New tire fixed it. On the GS, the cupping still happens, just usually don't feel wobble, but do feel a vibration in turns.
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Old 08-07-2012, 08:36 PM   #14
fritzcoinc
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Quote:
Originally Posted by cobrakai View Post
Getting some handlebar wobble around 70mph and above, more noticeable under power, on smooth straight asphalt. I understand I need to increase Rake/Trail. To do this, I should:

Increase rear sag (lower ride height)
Decrease front sag (raise ride height)
Lower forks in clamps (raise ride height)
Increase tire pressure in the...?
Change damping?
It's most likly the tire. Been there done that, got the Tee shirt.

Tires I have used and wobble coefficent ( 0 = none, 10= uncontrollable at 70+ ):
MT-21, 10
XCMH, 8
908RR, 4
Unicross, 0 ( PS: up to 95mph )

Two bikes tested, XR650L and TE610e.
Of course if your head stock bearings, wheel bearings, or swing arm bearings are shit, you have a problem.
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Old 11-21-2012, 02:17 PM   #15
gkgeiger
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Quote:
Originally Posted by GreaseMonkey View Post
Did you do anything like install panniers, or change the seat or handlebars? Does it ever go away, or is it always there?
I'm resurrecting this thread since I just developed this on my NC700X. The answer to greasemonkey's question is yes, I've done all the above. Did the bars first, no problem. Did the seat next, still no problem. Just installed panniers and top case today. If I take my hands off the bars it gets into a violent wobble instantly. If left alone it would turn into a tank slapper and I would crash. Up until today it was a steady as a rock. This machine only has 800 miles. I tried it with the panniers only, still does it but not as bad. I tried it with the top case only, same thing. If I take both off it doesn't do it but feels like it wants to. I know, don't take my hands off the bars, but somethings wrong.
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