High speed wobble

[2valve]

Hi Ken , Ive experienced first hand of the centred notched bearings/loose bearings/too-tight bearings, but when my /6 started to shake its head over the speed limit i just couldnt work it out, everthing felt good and no play evident. Heard about this retired bike mechanic that lived not far from my place ,made contact and he also went over the bike (he also owned a 90/6 back in the days) ,he recommended to change steering head bearings by this stage the handling issue was driving me nuts it was no fun at all. Should have kept that bike it was a rocket ship (for a BM ) , had Don Wilson do some serious work on the running gear it use to get up and boogie,as for the speed limit easily doubled plus on this bike in no time. In the end it was the streering bearings causing the fault but to me they felt OK. Hope Brad's mechanic gets on top of it and he reports back to tell us all about it.

[bbelk]

the bike didn't feel right in a turn. It seemed like I had to correct the pressure on the handlebars off and on to maintain the radius I wanted to follow. Ken

Yep

I suppose 'loose' bearings could promote wobble. (Editing: And too-tight bearings I would definitely associate with weave.) Ken

Definitely not lose. There is much more resistance to turning on the centerstand than my R65 which has newish steering bearings. I have tightened them in the past as they were quite lose when I got the bike. The weave/wobble did not present itself after that operation.

I suppose what I have been calling a wobble could be a weave. It does feel more like the full length of the bike and not just in the handle bars. I would put the pattern on the ground at a couple inches. Riders behind me could see it.

I would imagine that most here have read my article on wobbles and testing.

I have but I enjoyed reading them again. Thanks for re-posting.

Hope Brad's mechanic gets on top of it and he reports back to tell us all about it.

Me too and I will. I appreciate your input as well.

Off to the shop tomorrow.

[Major Softie]

I suppose what I have been calling a wobble could be a weave. It does feel more like the full length of the bike and not just in the handle bars. I would put the pattern on the ground at a couple inches. Riders behind me could see it.

The difference is more about speed and intensity. A wobble is a rather violent event, which can become extremely violent. A weave is a relatively gentle refusal to track smoothly.

[Duane Ausherman]

This was posted as a weave. It is not a weave, it is a wobble.

Here is one posted as a wobble, but it is a weave. See how the rear end acts? That is the key.

Another example of a weave that is called a wobble.

I have never encountered a weave that bad. I consider a weave to be more dangerous than a wobble. They are much harder to control, as once started they can exist over a wider speed range than a wobble. I think that weaves are quite rare on a BMW, or so it seems to me.

But, what do I know?

[bbelk]

This was posted as a weave. It is not a weave, it is a wobble.

I think you forgot some links and I would like to see them.

[bbelk]

The difference is more about speed and intensity. A wobble is a rather violent event, which can become extremely violent. A weave is a relatively gentle refusal to track smoothly.

I am still not sure it its a weave or a wobble. It is not instantaneous in its onset. It is not violent. It feels very much like it could get worse fast and is extremely unnerving. It goes a way at a speed slightly lower than its onset. Slowing down seems to be the only thing that makes it go away. It does not respond to breaking, turning, or accelerating. It does not always appear and seems to be a function of speed, road surface and wind.

[Zombie Master]

Back wheel spins true. I ran it up to about 60 on the centerstand and it wasn't jumping around..

That's funny! I mean you're not serious.

I was in a Ducati shop a few years back and they had a pretty 916 sitting in the service area. I had heard that they had weak side stands. I asked if they had problems with those stands. They said no so I continued shopping and purchased a helmet. As I was heading out the door I heard a crash, the stand on the 916 had failed and the 916 was less pretty. They looked at me very strangely, but I had not stepped into the service area. Moral: you never know when the center stand bolts will shear, it would be better it the wheel isn't going up to about 60 when it does.

[Duane Ausherman]

I didn't forget the links, they just didn't show up for some reason. I don't have time right now to go find them again. Sometimes I use Word and then just paste it, but not this time.

The first thing that I would do is examine the tires very carefully. If they appear to be round and straight, then I would check the balance. I know that you had them balanced, but in a motorcycle shop the newest person does tires. Even so, the best in a shop very rarely knows how to balance a motorcycle wheel.

My experience is that if you gave me 10 wheels that came balanced from 10 shops, I would find 8-9 that weren't done correctly. Very few people know how to do it, very few.

In all my years and motorcycles with wobbles, we were able to fix all high speed (over 60 mph) wobbles, but one of them. The owner couldn't afford to pay, so it didn't get fixed. A few still had minor low speed (25-45 mph) wobbles. Those were the ones with dual disc brakes. Those are very hard to get to perfect. Still, they didn't have high speed wobbles.

I have never seen a bent frame with a correct wheel base, but not track perfectly straight, cause a wobble.

All test riding must be done with no accessories attached. One may leave on the bag mounts and luggage rack, but that is all. A handle bar fairing is nearly sure to cause a wobble. Same with a top box. Bags and the top box can be empty and cause a wobble, a bad one too. Even the tiny R90S cockpit fairing caused instability on the Butler and Smith race bike. They frame mounted it and fixed it, but they never got caught by the tech inspection people.

We have been over this many times in the past years, so a search should show something.

[bbelk]

Back wheel spins true. I ran it up to about 60 on the centerstand and it wasn't jumping around..

That's funny! I mean you're not serious.

It would not have been pretty if it had failed, but it was in a front wheel chock and was well strapped to a motorcycle lift.

[Chuey]

Did the wobble start after the new tires? Do you have another bike you can borrow a front wheel/tire from?

When my bike wobbled (gently at about 40mph) it was the tire which was brand new. I put that tire on a different bike and then that one wobbled. The wobble was cured on the bike that had had the problem.

Chuey