Top box induced handlebar wobble

[Bounce]

Four FJRs and had a variety of marginal wobble...sometimes exacerbated by a top case.

Never thought of potential wear or damage on tire or bearings except for if you were to keep your hands of the bars. I think the point of muting that oscillation does away with any potential for damage...beyond a tank slapper of course.

I've heard and seen many theories and voodoo over the years including tire pressure, tire life, bearings, suspension settings, aerodynamics of the top case, tire pressure, weight distribution, sunspots, fiber rich diets, etc. I just know the four FJRs I've had all seem on the edge of it--sometimes better and sometimes scary.

My personal superstition rituals lean on front tire pressure, new tires better, but mostly weight distribution with more of it forward. That and Hermione told me the right way to cast the spell to stop it.

No-shimmi-o'sUH!

I always attributed it to a steep rake/trail than cruisers or luxo-tourers.

 

[harper]

PM Hudson, way back in my P brain I'm thinking he may have already went All Balls tappered set-up?

Good idea. He seemed to have done everything else. He made several improvements to that bike.

 

[RossKean]

Good idea. He seemed to have done everything else. He made several improvements to that bike.

Still worth making sure they are torqued properly. Too tight is often worse than too loose. I just went through that on my new-to-me BMW F700GS. Steering head was too tight and steering stability was poor. I set it at spec and it feels like a new bike.

 

[harper]

If your Ohlins rear shock has ride height adjustment, try adding a little bit of ride height. I am not talking about spring preload. If your shock doesn’t have ride height adjustment, try sliding your forks up in the triple trees 3-4 mm. See if that helps

I slid the forks up 4mm in the triple trees. I found an easy way to do that without removing the front wheel. If I use my imagination (and I use my imagination a lot because I imagined Penelope Cruz was riding as my passenger) I can see a slight improvement and, once started, the wobble damps by itself after a few oscillations. The turn-in is improved so I think I'll leave it like that. Also, I haven't thought of a clever way to slide the forks back down without removing the front wheel.

 

[RossKean]

Also, I haven't thought of a clever way to slide the forks back down without removing the front wheel.

Scissor jack under the header pipes with the bike on the center stand. I put a piece of 2 x 4 across the top so there isn't metal-on-metal.
(Or someone heavy to sit on the pillion seat to weight it down and hold your beer for you.)

 

[Lost]

+2 on the tapered bearings. Problems on my 2005 went away with tapered bearings. I'm with RossKean about liking them a little on the tight side. Starting from spec took me 3 or 4 tiny (1/32nd) turns to get where I wanted to be. Did this after some decent rides each time, may have been the bearings just doing the final seat with use. I didn't check torque at the end. My experience is parking lot weave is too tight, wobble around 35 mph is too loose.

 

[WoodyPecker]

FWIW, Here's something simple to consider. I always had a head shake around 40 to 45 miles an hour with hands off the bars, usually like Harper was because I would be adjusting something on my jacket or tightening a cuff. As some have noticed here it was less with new tires but would always return. This is on a 2016 with last few fronts as Michelin PR4 or 5, tho it was also with others like Dunlop. I do not use a top box so the situation is not quite the same as yours.
I went to a different shop the time before last to have a pr5 mounted on the front and he split the weights between left and right on the rim instead of all being on one side. That instantly fixed my head shake at that speed and I noticed it right away. Never returned for the life of that tire. This last time I took the rim in and had him mount a pr4 GT and he split the weights as before, and same again with no wobble at all now through 5000 miles on this one. I even happened to test it on a ride yesterday, as the acid test was always letting the bike decel on its own with hands off the bars down through that 45 mph range where I would always get a big wobble. Yesterday was nothing just smooth as glass.
I see several here have improved their stability with different head bearings or Fork position but I thought I would mention this tire weights as something that could contribute and is a simple thing to try. Finally I would mention that the total number of weights has been either two or three on each side when they were balanced, whereas before I might have four or five just on one side . Hope this helps

 

[user 90243]

Long ago I added front wobble to my Honda 500/4 by putting a tail trunk on it. Impossible to ride. Shook like the devil. Took it off. I thought it unweighted the front. And remember those muscular tire pressures 40/42.

 

[harper]

My new front tire balanced with no weight. I run 39/42 and have for years.

 

[CCook82]

As much weight in bags as possible. Less in top box will help. As will stiffer shock and / or more rear ride height if adjustment available.

 

[TomInPA]

I'll bet if you just slightly tighten the castle bolt on your steering stem, the problem would go away. DAMHIK.

 

[RossKean]

I'll bet if you just slightly tighten the castle bolt on your steering stem, the problem would go away. DAMHIK.

I agree that a steering head bearing that is too loose can be a problem with respect to stability - not to mention that the bearings can be more easily damaged by rough roads hammering the bearings into the races.

Not on my FJR but on my new-to-me 2017 BMW F700GS, the stock tapered steering head bearing was tightened too much by the original owner. It didn't feel especially tight when riding but it felt like I was riding on the top of a hump in the middle of the road and the bike kept falling off to one side or the other. Not dangerously extreme but there was a feeling that something wasn't right and more than an artifact of it being a very different motorcycle than my FJR.. With the bearing too tight, the wheel stayed where it was pointed instead of naturally returning to center. This meant that I was constantly correcting when riding at low speed. Too tight is as bad as too loose. Once I set it at the correct torque, it felt like a new bike.

 

[mcatrophy]

A typically unhelpful mcatrophy comment.

I have an OEM 50 litre topbox on my 2018, it was on my 2014. It stays there all the time, usually empty. Never had a passenger or rear seat luggage to break the airflow. I've never noticed any of the wobble issues several others have talked of, but I think the bike’s more sensitive to blustery winds with it on.

Parameters that might be relevant:
Suspension is the OEM electrically adjustable (AE in the USA; ES, and on the AS in the UK), almost invariably set for rider only, no luggage, standard damping;
Windscreen: Yamaha touring (no issues at any height setting, though never set high enough that I can't see over it);
Rider weight: 140 pounds (that's in my birthday suit, though I usually ride in a full motorcycling suit);
Rider height: 5'7" when last measured (was 5'8.5" for most of my life);
Tyres: BT023 or T32, pressures 39-40/42-43, though a few psi under doesn't cause wobble, just affects handling);
Speeds: often in the 80s (must be on private roads), occasionally a few minutes at nearer jail speeds, though in that case I usually have maybe 20 pounds in the topbox.
Head bearings: I’ve never checked them, they are as they came from the factory, the bike is serviced at my dealer, I don't know if he has ever adjusted them. With the front wheel off the ground, the bars flop side-to-side with no friction other than cables. Since I get no symptoms of head bearing issues (I don't consider handlebar wobble when decelerating through the 40mph area an issue) I leave them alone.

I do understand how the topbox might add eddies from round the rider (you've only got to look at a flag fluttering in a steady wind to visualise that possibility), just never experienced it.

I am thinking rider bulk in particular might be something to do with it, I am smaller than most riders.

As I say, probably of no help at all, maybe just some sort of data point.

 

[Fred W]

Hmmm. Sliding the fork legs up would steepen the steering angles, which should make the front end less stable and more prone to oscillate. It would make the bike turn-in quicker.

Adjusting the preload is the same thing as ride height. You can raise or lower either end of the bike by increasing or decreasing the preload adjusters. That is what preload is there for. It won’t affect the spring’s rate or stiffness at all. It can’t.

Both of my FJRs have always wobbled at hyper-legal highway speeds with a top case and no passenger. I generally only put the top case on when I have a passenger, but have sometimes wanted the extra space for solo vacation trips, and always feel it then. Never noticed it at slower speeds though.

 

[harper]

A typically unhelpful mcatrophy comment.

I always find your comments and write-ups to be useful, well thought out, and informative. I also have lost 1.5 inches in height. The waist circumference, however, continues to increase.

Both of my FJRs have always wobbled at hyper-legal highway speeds with a top case and no passenger. I generally only put the top case on when I have a passenger, but have sometimes wanted the extra space for solo vacation trips, and always feel it then. Never noticed it at slower speeds though.

When I get into the 60 to 90 mph range the wobble seems to go away. I haven't tried above that.

 

[Fred W]

When I get into the 60 to 90 mph range the wobble seems to go away. I haven't tried above that.

Weird. That’s exactly where I feel it. Must be a difference in windshields. Years back when we were visiting the open roads of Wyoming and Montana, I wicked it up past 100 one morning with my wife on the back and the trunk as her backrest. No buffeting at all. She didn’t even realize we were going that fast until I told her later.

 

[harper]

I bought and received a castle nut socket for the FJR. It came from mcatrophy's side of the pond so it took awhile to get here. It's simple to use and you apply torque from the center rather than off to the side like you do with a spanner. My headset is now correctly torqued and it made a noticeable reduction to the handlebar wobble in the 30-40 mph range without seeming to move the wobble to higher or lower speeds.

 

[Panman]

Bearing still feel smoth? Did you ever find out if Huddy went All Balls on that thing?

 

[Zerofun]

I bought and received a castle nut socket for the FJR. It came from mcatrophy's side of the pond so it took awhile to get here. It's simple to use and you apply torque from the center rather than off to the side like you do with a spanner. My headset is now correctly torqued and it made a noticeable reduction to the handlebar wobble in the 30-40 mph range without seeming to move the wobble to higher or lower speeds.

What did you use as the torque spec from the center?

 

[harper]

What did you use as the torque spec from the center?

The first torque setting is 37 ft-lbs, then fully loosen the nut, then the second torque setting is 13 ft-lbs.

The torque arm of the torque wrench itself is 17". The torque arm of the torque wrench with a spanner at 90 degrees with 3" arm is 17.25". This is within 1.5% which is better than the accuracy of the torque wrench.