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Old 04-07-2010, 7:34 AM   #1
 
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Stability/wobble isues

Hello all,

A few months back I began to have some issues with my steering. It wasn't anything major, just that the bike was beginning to feel a bit unstable, especially with subtle maneuvers like changing lanes etc. The bike felt like it wanted to fall so to speak, to turn more than I intended to. It's hard to describe but in any case it didn't feel right. It might have been due to the road being more slippery or just in my head altogether but in any case I nagged to my mechanic about it and he recommended tightening the steering bearings so we did that and then the bike didn't feel strange any more, it just turned into a clock and started rocking from left to right like a rowboat or a pendulum on a grandfather clock. It was fun for a bit but it started to get annoying so I put new steering bearings in (upgraded to tapered roller bearings) as you could feel the old ones having trouble around the straight ahead position. (With the front wheel airborne and turning the steering head slowly you could feel it snapping to straight ahead position as soon as you got to within a few degrees from it).

From that point on the bike has never steered well again. I've tried adjusting the preload on the bearings about a hundred times. The steering either feels vague when the bearings are loose or starts to wobble like a rowboat when I try to tighten them and this has been going for months now. The effects aren't always very pronounced. It depends on the quality of the road, the preload on the bearings or other parameters I'm unaware of but in any case it feels weird or not like I remember it used to. I'm completely stumped as to the causes. Either I'm getting the steering bearing adjustment completely wrong, or I'm not carrying out the procedure correctly, or the problem is not steering related or it's all in my head and I need that checked first.

I'm at the point where I think that the best approach is to inadvertently check if I have any fuel left with my lighter. That should fix all my problems.
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Old 04-07-2010, 12:04 PM   #2
 
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Re: Stability/wobble isues

Have you checked the basics? Tyres basically. Are the pressures correct? Also are they worn? As tyres wear the bike can handle very differently, especially towards the end of the tyres life and if they lose their profile.
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Old 04-07-2010, 2:14 PM   #3
 
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Re: Stability/wobble isues

I've checked everything I could think of after googling for issues like this. The tires are properly inflated and are in good shape as I've had them for a few thousand kilometers. The old tires were in pretty bad shape but I had no such problems (although the bike did behave like a sled but that's another issue). I've tried to play around with preload and damping settings on forks and shock and although they do make the bike behave differently they don't really change the situation. The wheel bearings have been changed recently too and the swingarm bearing seems to be ok. Either the steering bearings are badly installed or there's something about adjusting them that I don't get. But anyway, as far as I understand it, and unless you have set the preload on the steering really tight or really loose the bike shouldn't exhibit funny behavior during relaxed driving. I mean getting a tank-slapper at 180kmh or during heavy acceleration or breaking is one thing but getting sustained oscillations when coasting at 20 or 30 kmh shouldn't happen that easily. I may be completely mistaken but the truth is I don't know. My main problem is that this may be caused by a lot of different problems. The fact that it's relatively subtle, depending on the steering bearing setting means also that it may have been there in the past but I didn't give much attention to it until it became evident enough for me to decide to change the bearings. So I can't assume it's due to something I did since then. So the only approach I can see is starting to check/change anything I can think of including things such as fork oil, fork spriings/spacers, wheel bearings, swingarm bearings, shock bearings etc. etc. and this still gives me no guarantee that the problem will go away. So in the end I think that the lighter to the gas tank approach is both cheaper and less painful. I hope someone in here will have a better idea.
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Old 04-07-2010, 4:05 PM   #4
 
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Re: Stability/wobble isues

This may be the cowards way out, but if you dont want to troll through the all the tiny issues that could be causing this issue or pay a mechanic to do it for you. Then maybe you should cut your losses and sell the bike? I'm sure thats a better solution than the light - tank approach lol.
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Old 04-08-2010, 4:33 AM   #5
 
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Re: Stability/wobble isues

It's not that I don't want to pay a mechanic to fix it. It's that I don't trust anyone to fix it. As I've said the problem can be made subtle by loosening the steering stem and then steering vagueness is subjective. In fact I had my mechanic (who I generally respect although I don't trust mechanics) adjust the bearings when I first installed them. After feeling the steering with the front wheel in the air I asked whether this was maybe too stiff. He said the bearings would settle and it would loosen. So I took it for a test ride and the chassis would oscillate back and forth really badly as soon as you opened the throttle. So I loosened the bear it would still wobble a bit but I waited a couple of days for the bearings to settle. After not noticing any difference I loosened it a bit more and the wobbling went away but it would still handle badly. To be fair I must say that he did warn me not to loosen it further. But I couldn't leave it as it was either.
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Old 04-08-2010, 5:04 AM   #6
 
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Re: Stability/wobble isues

Newish tyres? (Thats tires for you Americans). Try setting your speed at about 30mph (KPH?). Let go of the bars. If they start to occilate then I can garantee that you have a tyre issue. I've had this so many times on many different bikes. Something about the tyre construction that is not quite right, No amount of wheel balancing can cure it either.
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Old 04-08-2010, 5:20 AM   #7
 
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Re: Stability/wobble isues

It may or may not oscillate. I'm aware of this issue but I don't seem to have it. It oscillates whether I hold on to the clipons or not. I can go no-hands without the bike oscillating some times, other it will oscillate with or without hands. It depends on the pavement I think. I think the problem is that the steering doesn't have the self-correcting action it's supposed to have. If some anomaly in the road forces the tyre to swing left for example it will swing right instead of centering and continue until you dampen the steering head with your hands. But then again steering effects are so complicated that I'm probably wrong. I'm relatively sure that the problem is there whether I hold on to the bar tightly, loosely or not a all.
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Old 04-08-2010, 6:23 AM   #8
 
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Re: Stability/wobble isues

Only one other option then. If you have eliminated all the probables then its Back to square one. This started with a change of headbearings... so.... there is something wrong with the head bearings!
Maybe they have seated slightly cockeyed, maybe a faulty bearing set (and that does happen). Take them out and try another set making damn sure they seat properly.
Its no big deal to do, If you need help, shout.
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Old 04-08-2010, 8:39 AM   #9
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Re: Stability/wobble isues

Originally Posted by jdugen View Post
This started with a change of headbearings... so.... there is something wrong with the head bearings!
Also have the right ones been fitted?
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Old 04-08-2010, 9:03 AM   #10
 
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Re: Stability/wobble isues

Not nice Im sure and to be honest hard to pin down if your not there as you seem to mention most things that could be the problem. I can only add to the questions. Although the bearings do seem to have a bearing in this issue, overtightening does not help and maybe you have created a small dent in the bearing cup.

Also maybe other things are coming into play. Have you dropped or crashed the bike at all perhaps twisting forks or the head as it sounds like your trying to over steer? Are your wheels in line? Are your bars level? Oscillations could be out of balance wheels, wrongly fitted tyres or just bad roads, try a different route in your tests. Have you checked the rear shock and swinging arm as it could amplify a problem making you think its the front end. To be honest start with the bearings then go over each and everyone of the things mentioned in all the answers.


good luck and tell us how you get on.
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Old 04-09-2010, 5:13 AM   #11
 
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Re: Stability/wobble isues

Well I have to assume the bearings are correct. It's hard to ask a mechanic if he installed the right bearings or if he knows what he's doing in other words . I don't think I've tightened them enough to damage them. AFAIK it takes some time for them to wear even when they're overloaded. I haven't dropped the bike recently so the forks, clip-ons, swingarm etc. should be as straight as they ever were. I'm not sure how straight that is but in any case it doesn't explain this behaviour. My tyres are unbalanced but they were from the start and it didn't cause me any trouble then so I assume that's not it either. The rear wheel seems to be ok in terms of bearings and there doesn't seem to be any play in the swingarm.

Do you guys know of any way to check the bearings that doesn't involve 'feel'? The only thing I haven't tried actually is to perform the adjustment exactly by the book which involves tightening the bearing until all play is removed in the forks. How do you do it? Is there some way to check for play in the forks without having some sort of dedicated stand? Is there some other way to adjust the little suckers that doesn't rely on magic or feel? I was thinking of removing the top yoke as the manual suggests, completely loosen the adjuster nut and check for play in the forks. If I can feel any then I'll just keep tightening until I can't then install the locknut as the manual suggests and the top yoke. The only way of raising the front wheel I can think of is pulling the bike up on its sidestand. I doubt I'll be able to feel any play with the bike in such an unbalanced position.
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Old 04-09-2010, 6:02 AM   #12
 
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Re: Stability/wobble isues

Aha. Yes, the ONLY way to set up your head bearings is with the front off the ground. There are front stands that will cost you money, you could put a jack under the engine, but that might damage exhausts. The best way is to find a sturdy roof beam in yours or a friends garage and get a cheap ratchet hoist. A piece of good rope can be slung under the frame at the headstock end and then the front lifted clear. You can then do your bearing adjustments properly., (as well as being able to get to all the front end components for your next brake overhaul).
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Old 04-09-2010, 6:29 AM   #13
 
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Re: Stability/wobble isues

I adjusted them with the front wheel off the ground but to do that I pulled on the tank in order to balance the bike on the back wheel and sidestand. The front wheel was airborne alright but the bike was in a sort of tilted position. The front stands I've seen lift the bike by its forks so it wouldn't be useful in checking the forks for play or the steering. I've seen the jack method done at the shop but that balances the bike on the rear wheel, sidestand and jack so its still tilted. It might be more stable though. The main matter is: how do I adjust the bearings once I've got the front wheel in the air? If there was a way I could be more or less certain that the bearing was not far off and the bike would still wobble I could at least start looking elsewhere.
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Old 04-12-2010, 6:44 AM   #14
 
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Re: Stability/wobble isues

Well after some more adjustment (and after almost taking the whole steering head apart by mistake) I'm now more or less happy with the result. I took the top yoke off and completely loosened the adjuster and lock nut. The I tightened it again until the steering head started to get stiffer. I then backed it up until the steering felt free again.

For anyone who's having similar trouble I must say that you have to be careful with the way you use the locknut. You don't jam it against the adjuster nut. I think it'll do its job this way but you'll probably mess with your adjustment when tightening the locknut as it will also turn the adjuster nut. You may mess with it even further when you torque the top yoke to the manufacturer's specifications. You can still get a decent result this way but it gets much more complicated and you'll have to guess how stiff the steering will become once everything is in place.

What you should do instead, I think, is this: Tighten the adjuster nut until the steering feels right (whatever that is) then align a couple of the tabs on that lock washer that is between the nuts with the slots in the adjuster nut and bend them downwards into it. Then put the locknut on and tighten it finger-tight. Carefully tighten it further as much as needed to align a slot on the locknut with the remaining tab on the washer and bend it upwards. The manual says you shouldn't tighten it further than 90 degrees past fingertight.

What happens now is this. When the top yoke is tightened to 105Nm it locks onto the locknut thus not allowing it to work itself loose. This in turn keeps the adjuster nut in place through the tabbed washer. I think it also serves the purpose of isolating the adjuster nut from the pressure of the top yoke but in any case once everything is tightened this way the steering is affected only by the adjuster nut.

Where was I? Ah yes, so loosened it again until it felt free. On the way home the steering felt vague again, regardless of speed. At least it didn't wobble. So I tightened it a little more (without obeying the procedure above because I was too lazy to take of the yoke, thus ruining the tabs on the washer), anyway I tightened it a little more so that the steering was just beginning to stiffen. When lifting the front wheel on the sidestand as previously described the steering would just smoothly fall to full lock without banging on the stop. It feels a lot better now. Especially for speeds higher than say 50kmh the steering is much more defined. The bike still slides around but that's due to the roads here reflecting the vehicles even when dry.

I'm closing the case. Hope all this blabber will be of use to someone with similar issues.
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