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Old 03-23-2014, 10:09 PM   #1
ccmickelson OP
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Steering Wobble Willies

Looking for some input/advice related to steering wobble on my RS. Periodically, at low speeds, (thankfully) when I take my hands off the bars momentarily the front end goes into a wobble, which I imagine would escalate into a full on tank slapper if I didn't get my hands back on quickly enough. At highway speeds the bike is solid as a rock...nary and shimmy. It happened again riding home a few days ago. It is very unpredictable and unsettling to say the least.

I'll also add that this is a phenomenon I have experienced with eight or nine of the dozen or so airheads I have owned over the past twenty five years. I've never experienced this with any of the Japanese bikes I've had, only beemers. I am wondering if it has something to do with what I am doing (aside from riding with no hands) or not doing with my bikes.

I am reasonably confident my steering bearings are greased and adjusted properly and I know my tire pressure is good. Wheel bearings good. Wheels balanced. Fork clamps tight, springs and oil in good shape.

What the heck??? Any advice would be greatly appreciated.
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Old 03-23-2014, 10:27 PM   #2
Big Bamboo
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Are you running with a top case or bags? Duane Ausherman has a good write up on various causes and solutions: http://w6rec.com/duane/bmw/wobbles.htm
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Old 03-24-2014, 01:37 AM   #3
ME 109
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Got to start with a full fork alignment. If you've never done it, you don't know where it's at.
Tyre pressure should be approx 35. Below 30 is too low. My steering head bearings are shot, but the bike won't wobble at low speed. That heavy snowflake does a lot to stabilise the forks. IMO.
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Old 03-24-2014, 02:34 AM   #4
Bill Harris
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Even though you are sure that the steering head, wheel and swingarm bearings are "good", go back and double-check them and their adjustment. Something is amiss. and those are the areas to check. And a tire, well into it's life, can start to cup and create a low-speed shimmy.

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Old 03-24-2014, 02:46 AM   #5
boxerboy81
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Tyre pressures too low and tyres due for a change will accentuate the slow speed wobble on my RS.
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Old 03-24-2014, 03:06 AM   #6
motu
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My '87 has never had a wobble in the more than 5 years I've had it - until I fitted the S fairing and standard bars a couple of months ago. Everything exactly the same as before, but now I get a small shake slowing down for an intersection...hardly noticeable, but you can see the bars wobble if I take my hands off.
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Old 03-24-2014, 03:32 AM   #7
Jim Day
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Quote:
Originally Posted by Big Bamboo View Post
ADuane Ausherman has a good write up on various causes and solutions: http://w6rec.com/duane/bmw/wobbles.htm
That is a intense read....


".....I started the high speed tests at 50-55 mph and it showed no instability at all. I repeated it at 60 and it was as solid as a rock. I did the same at 65 mph and the forks went into a full wobble instantly. There was no time to do anything. Had my hands been on the bars, my fingers would have been crushed by the wildly swinging bars. The front tire was skipping and airborne. It would come down at the end of the travel and make a huge squeal. The front wheel would become airborne again and head for the other stop. This happened about 10-12 times in maybe one or two seconds. I wasn't paying close attention to my watch. My only reaction was to try to sit down again. Due to the added biomass, or some unknown factor, the bike snapped out of the wobble. It dampened out as fast as it started.I immediately stopped and got off. I was so scared and weak kneed that I could barely put it on the center stand......We examined the tire tracks. Every 15-20 feet there was a 2 foot black mark and each was about 90 degrees from the previous one. The marks weren't straight, but oddly shaped. You could see where the tire smashed back down on the pavement with a wide part and then the traction and trail forced the wheel to correct. This correction was enough force to whip the bike back into the air with the tire again off of the ground. If one drew a line through all of the "left" tracks and another through the "right" tracks, they were about 3-4 feet apart....."

"Fork "Me!!! that is INSANE!!! stuff.

I've never experienced a high speed wobble though my old R60 would do a light low speed wobble if you let go of the bars.

Every time I play with a fork I do that initial high speed test where I take it up to 90+ waiting to see if anything goes wrong. No issues yet but just the thought of a high speed wobble scares the hell out of me.

My R65 chopper you can ride like a bicycle no hands but I've been to cautious to try that with the R100R.
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Old 03-24-2014, 03:37 AM   #8
Jim Day
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Quote:
Originally Posted by motu View Post
My '87 has never had a wobble in the more than 5 years I've had it - until I fitted the S fairing and standard bars a couple of months ago. Everything exactly the same as before, but now I get a small shake slowing down for an intersection...hardly noticeable, but you can see the bars wobble if I take my hands off.
In the link above Daune talks specifically about fairing and bar changes that can cause wobbles. Worth the read.

Jim Day screwed with this post 03-24-2014 at 05:37 AM
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Old 03-24-2014, 05:57 AM   #9
RagerToo
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Quote:
The only thing that we found wrong with this new motorcycle was that the forks were not in alignment. It showed very little stiction. The forks were .006" out of alignment in both planes. The BMW spec was .004" and so it was very close. We had been aligning forks for about a year to .002", but we had never suspected that such a small error could cause such a wild wobble. We changed our previous spec to .001" or better. After all, what is wrong with perfect? The alignment procedure fixed the bike and it never gave a problem again.
Fellas, thanks for posting these articles. I can't get my head around "both planes" though. I understand "twist" in the triple tree. The "other plane" would be overall lengths of the individual tubes (assembly), full extension, no axle installed? Thanks.

*** Heck, I'm tryin' to remember if I checked my top tubes for straight when I had them apart. grrr
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Old 03-24-2014, 07:00 AM   #10
ccmickelson OP
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Quote:
Originally Posted by Big Bamboo View Post
Are you running with a top case or bags? Duane Ausherman has a good write up on various causes and solutions: http://w6rec.com/duane/bmw/wobbles.htm
I use bags but only on trips. This can happen with or without bags.

And the frustrating thing is it doesn't always happen. I went out yesterday and came back on the same road it happened the other day and at the same speed it happened before (30mph or so) cautiously took my hands off the bars...and no wobble. Not even a shimmy. I even gave them a light bump to see if it would initiate the wobble. Nothing. I don't get it.

I run the tires at the recommended pressure 32 in front and 36 in back if I remember correctly. The Metzlers have 3.5K on them so maybe tire wear is the culprit. I regularly check the steering and swingarm bearings so I don't feel that is causing the issue.

I have never done a fork alignment but that sounds like something I really should look into.

Thank you for all the great feedback.
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Old 03-24-2014, 07:11 AM   #11
Rob Farmer
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The back end is too high. Drop it down a notch on the shock absorbers and see if it makes a difference. if it's too soft buy new shocks.

The Twin shock RS's hate having their arses too high in the air.
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Old 03-24-2014, 07:25 AM   #12
op48no1
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I've owned three monolevers and they all had/have a low-speed wobble. If I take my hands off the bars and hit the grip, then let go, it goes into a sustained but self-limited wobble. I can ride down the road like this (throttle friction screw). Riding companions find it amusing. At speed the bike has the usual 85MPH light-feeling front end, but nothing out of the ordinary. This is in naked configuration. Swingarm, steering bearings, and tires are OK. The effect does vary with tire wear.

I agree this isn't ideal, and maybe not normal. But if everything checks out, it may not be atypical. Which model do you have?

-Henry
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Old 03-24-2014, 07:58 AM   #13
airsmith
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I've done the fork alignment to about 15 bikes over the years, with noticable improvement in all cases, my wifes beast which breaks all the handling rules. big windjammer fairing, luftmeister trunk, huge givi bags and always overloaded will only start a little speed weave at well over 85.. most bikes should get this looked at.. (its a good time to renue all the fork seals and bits) the make our break part of the operation is the tightening of the 36mm top nuts(you can mess up all your good work in this step), most likely the poster that stated my bike was fine untill the S-fairing was added , had more to do with the correct method of tightening the top nuts than the fairing..
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Old 03-24-2014, 08:17 AM   #14
ccmickelson OP
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Quote:
Originally Posted by Rob Farmer View Post
The back end is too high. Drop it down a notch on the shock absorbers and see if it makes a difference. if it's too soft buy new shocks.

The Twin shock RS's hate having their arses too high in the air.
This is a mono RS but I will give this a try anyway. I'm running a Progressive 420 and I believe it sits a bit higher than the stock setup. No problem with softness front or back.
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Old 03-24-2014, 08:38 AM   #15
ccmickelson OP
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Quote:
Originally Posted by op48no1 View Post
I've owned three monolevers and they all had/have a low-speed wobble. If I take my hands off the bars and hit the grip, then let go, it goes into a sustained but self-limited wobble. I can ride down the road like this (throttle friction screw). Riding companions find it amusing. At speed the bike has the usual 85MPH light-feeling front end, but nothing out of the ordinary. This is in naked configuration. Swingarm, steering bearings, and tires are OK. The effect does vary with tire wear.

I agree this isn't ideal, and maybe not normal. But if everything checks out, it may not be atypical. Which model do you have?

-Henry
It's a '93 RS and does as you describe although I've never had the nerve to let the wobble continue long enough to see what happened. I also can't seem to initiate it at will as you describe. Maybe I'm not hitting the bars hard enough?

Another observation I've made is it seems to only ever happen on flat or downhill sections of road.

I remember well the first time I ever felt such a wobble was on an '81 RS in the early 90s. I was moto-marshaling a women's bicycle race in Idaho and we were cruising along at 30 mph or so. I took my hands off momentarily to unzip my jacket and it started. Scared the shit out of me. After the race, I went straight to a beemer shop in Boise to have it looked at but they couldn't find anything wrong.
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