Top box induced handlebar wobble

[harper]

I have a new-to-me 2008 FJR. I have recently been fighting a problem with handlebar wobble which I noticed when I briefly took my hands off the grips at 30mph to tighten my glove straps. I found this oscillation at almost any speed on almost any surface if I removed my hands from the grips. The bike needed tires so I replaced them which made a difference but only reduced the oscillations and the conditions under which they would occur. I then began altering first the front suspension and finally the rear shock. Again, this seemed to move the problem around but not eliminate it.

I researched causes of this problem on several motorcycle fora to determine if I needed to address the headset bearing or the wheel bearings next. During this I came across several posts that directly correlated top boxes to handlebar wobble on several different bikes of different sizes. I had never had a top box before this bike so I pulled it off and the effect went away entirely. I couldn't get the oscillations to start at any speed over any road surface.

This raises a question: If I am riding with a top box and am damping the oscillations that are trying to form with my hands, is any damage being done to the front tire, the wheel bearing, or the headset bearing? I like the new convenience of having a top box but it is unnerving to take my hands off the handlebars and have that wobble start up. It's even worse if it's actually doing damage.

 

[Oldjeep]

Seems weird. I run the biggest luggage known to FJRkind and don't get any vibrations with my 52L top box on. Might want to check your headset bearings and consider replacing with tapered bearings.

 

[dcarver]

I have another top box I'll sell yah!

No damage AFAIK. I installed tapered Timkin bearings on both FJR's (06, 13) and never had the issue again.

 

[Ignacio]

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!

 

[SwollenRaccoon]

This has been discussed before, with as many opinions as there are members. MY two cents...aerodynamics. Top box on and a pillion along, zero vagueness. Top box on and an empty rear seat, occasional but not severe or frightening "wandering". It has to be aerodynamic, barring steering head or tire/frame issues, since the problem goes away with a passenger, which would actually lighten the front tire load. When I have some luggage on the rear seat, the problem is less noticeable than when the seat is empty. The top box, with an empty pillion seat, seems to act just like a wing on a race care, adding downforce (more likely "drag" than downforce) to the back of the bike, and lightening the front, more so even than adding a passenger to the back. I have been into triple digits many times with the top box on, and felt it many times, but it never felt dangerous.
Remember, this is just my opinion, which is worthless. Ride the bastard, and ride it hard.

 

[RossKean]

Yamaha top box?
I haven't noticed oscillation with my Givi V46 although sometimes a slight tendency to "wander" a bit.

 

[Panman]

My 07 has always had a bit at slower speeds and going down hill seems to aggravate it but never at speed. Slight touch of the bars and it's gone.
I have the Yamaha top box and never an issue at speed with any top box wobble even at speeds that I won't talk on a public forum.

 

[harper]

I have a jumbo Givi Monokey but I don't know which model so I don't know the volume.

I had heard of the aerodynamic theory but Swollen Racoon apparently has good reason to think it may be the explanation. Given the shape of the Givi I would be more likely to believe that side-to-side forces are exerted on it rather than a downward force that would lighten the front end.

I'm good with riding with it as long as I think no damage is being done. I will, however, miss the ability to close the top snap of my coat at 70mph.

Thanks for the replies.

 

[RossKean]

You might try a different windscreen. It is part of the total package that defines aerodynamic properties.
Alternative might be to get a blow-up passenger to fill the gap.

 

[user 213]

@harper - since no one asked, are you riding with or w/o the side bags? And how many miles on the bike? (why is it people forget to ask questions before they want to give a suggested answer?)

There is a two stage process of re-torquing the steering head bearings. Most people don't do it right, if they do it at all. And FJRs tend to get loose steering head bearings at some point. You need a special wrench, but it's otherwise an easy process.

 

[harper]

Side bags on. 42k miles. Only 600 miles are mine so I just started experimenting with it.

 

[harper]

You might try a different windscreen. It is part of the total package that defines aerodynamic properties.
Alternative might be to get a blow-up passenger to fill the gap.

Blow-up passengers tend to be blow-away passengers as well. I suppose I could fill a red hot, overly made up, scantily-clad, blow-up doll with body temperature water.

 

[Sunnyorlando]

I also have a bit of this on my '18, but not of a concern as I usually ride with my hands on the handlebars.
New tires make a bit of difference for a while, but it does return. It's always at about that 30~40 mph range, I've never had it happen when I take may hands off at 80+ mph.
Sometimes it gets fixed with the tapered bearing option, and sometimes not.
As probably many (if not most here), i have many other bikes that have done this, even new ones. It concern me more at the beginning not understanding why, but over time I've come to accept that this just happens to some degree with most larger bikes.
From what I have read and personally tried over the years, it appears to me that nobody has ever come up with conclusive root cause, and there's no exact single fix (that I know of) for any of them - except keep your hand on the handlebars, at least at that speed where it happens .

 

[EddieB]

My only top box issue is aerodynamic, I think. Feels unstable with the top box on and riding solo in heavy trucker traffic on the interstates in Texas at 70+mph. The only solution for me has been to get off the interstates and ride back roads without the turbulence of the trucks. It's much more enjoyable anyway even if a bit slower.

 

[harper]

I wonder if bar end weights would work to reduce the effect.

 

[redneckj]

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

 

[keithq]

I have another top box I'll sell yah!

No damage AFAIK. I installed tapered Timkin bearings on both FJR's (06, 13) and never had the issue again.

I would 2nd the opinion on tapered bearings. The Honda ST1100 had similar issues with head shake. Vicious at leaving-the-highway speeds. Completely fixed, top box or not, with a change in bearings.

 

[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

The Ohlins doesn't have ride height adjustment.

 

[Ignacio]

I wonder if bar end weights would work to reduce the effect.

Nope.

 

[Panman]

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