Weird handling after GIVI top box

[audiowize]

So I installed the GIVI specific rack on my 2004 FJR yesterday, and popped on E52 that I got locally for a good price.

This morning, I head off down the road, and as soon as I exceed 60 mph, I can immediately feel some side to side movement that wasn't there yesterday. This is bad enough on the freeway that I exited to check tire pressure, as the bike really didn't want to track in a straight line. Tire pressures are all where they should be (36 front, 40 rear, just as it was when I purchased the bike).

Doing some searching, there are some complaints about this problem, but not a lot of resolution other than sticking a passenger on the bike. Apparently it also doesn't help that I have a V-stream windscreen.

Any ideas?

What mechanism is at work? Is this air coming up, over, and pushing down on the box, or is this air coming around and pushing on the sides of the box?

 

[mcatrophy]

So I installed the GIVI specific rack on my 2004 FJR yesterday, and popped on E52 that I got locally for a good price.
This morning, I head off down the road, and as soon as I exceed 60 mph, I can immediately feel some side to side movement that wasn't there yesterday. This is bad enough on the freeway that I exited to check tire pressure, as the bike really didn't want to track in a straight line. Tire pressures are all where they should be (36 front, 40 rear, just as it was when I purchased the bike).

Doing some searching, there are some complaints about this problem, but not a lot of resolution other than sticking a passenger on the bike. Apparently it also doesn't help that I have a V-stream windscreen.

Any ideas?

What mechanism is at work? Is this air coming up, over, and pushing down on the box, or is this air coming around and pushing on the sides of the box?

Round you and the box. Try a soft bag strapped to the passenger seat, anything to break up the air-flow.
Don't try to ride through it, you may not succeed.

 

[FJReady]

I think its the turbulent air going around your body and getting in front of the box. The problem will likely go away when you have a passenger. Of course you'll have other problems then.

Usually the "Top Box High Speed Weave' occurs at much greater speeds than 60 mph. I have experienced it only near triple digit speeds. So there are othe factors involved I'm sure. Rider size and windshield size probably are big factors.

 

[Niehart]

Tire pressures are all where they should be (36 front, 40 rear, just as it was when I purchased the bike).
Any ideas?

That tie pressure is to low. 39/40 front, 42 rear.

 

[Mihalis fjr]

Nο problem with the oem top box..Νever have had a like this issue..

 

[majicmaker]

It happens with the OEM box too, Mihalis. It's the wind turbulance in the gap between the rider and the box. It's normal but, I've never experienced it at 60. It's more toward the triple digits on mine. Anything you put in the passenger seat will make it go away. It doesn't take much. My smuggler makes it go away.

 

[fjrbird]

Strange. I ride with only top box (givi), no side bags, every day, commuting to work or twisties with no issue or noticeable turbulence. My windshield is stock. Perhaps my short stature (5'5) helps? The only time I want to remove the box is for the bike to be more sporty look!

 

[garyahouse]

I've got a Givi 55 on a 357 Givi rack on my 05: and I've got a CeeBailey 4+2 reverse flip. This pic was with my smaller Givi which I sold just after this picture was taken in the summer of 2013.

With the windshield up a couple inches, my FJR does it's little dance around 100 as well. It gets real interesting when passing in and out of the turbulence close behind a truck at that speed. Not that it matters, actually it's happened like twice... but I never travel those kind of speeds or that close to trucks most of the time. That was kind of a one time-type thing, if that makes sense. Took place while trying to keep up with a friend one day. Glad I don't do that often. Those kinds of speeds don't agree with me, nor with the local neighborhood boys in blue.

I did notice that putting the windshield back down helped somewhat.

Gary

darksider #44

 

[bikerskier]

Put an E52 on my '05 just prior to starting my big ride 3 weeks ago. Have over 8000 miles so far in these 3 weeks and I have no problems with the box at any speeds.

 

[bluesdog]

iirc, the owners manual does not recommend speeds in excess of 80 mph/130 kph with panniers and/or trunk attached.

I've noticed the handling is a bit more 'twitchy' at speed with the panniers, but since I don't have a top box cannot comment from personal experience.

As others noted, rider height/weight, rider body position, windshield configuration, and tire pressure all affect handling. The aerodynamics introduced by panniers and trunk would tend to influence things as well.

It would be interesting to do some controlled tests, changing the variables...

 

[RadioHowie]

It happens with the OEM box too, Mihalis. It's the wind turbulance in the gap between the rider and the box. It's normal but, I've never experienced it at 60. It's more toward the triple digits on mine. Anything you put in the passenger seat will make it go away. It doesn't take much. My smuggler makes it go away.

*******!!!

 

[escapefjrtist]

Experienced the "weave" with my V46 for the first time a couple weeks ago heading to the Reuben Run. Didn't happen until speeds were, well...shall we say elevated.

Recently had the Penske rebuilt / resprung so more experimenting is needed...

--G

 

[900gc]

I think the "hole" in the air from the shield collapses (or starts to) around the top box causing the turbulence. The size, shape, adjustment level, etc. of the shield, and speed of course, has a bearing on the amount experienced. Your V Stream probably does contribute more due to a larger "hole" that is collapsing. A pillion bag or passenger acts to help streamline the collapse and push it back behind the box.

I have an E55 and my CB 4x2 reverse flip shield causes a little wag at 75mph if I'm solo, so I only use it for long trips with my wife on back. No issues then.

 

[Mihalis fjr]

It happens with the OEM box too, Mihalis. It's the wind turbulance in the gap between the rider and the box. It's normal but, I've never experienced it at 60. It's more toward the triple digits on mine. Anything you put in the passenger seat will make it go away. It doesn't take much. My smuggler makes it go away.

I have never tried to go with the top box at the triple digits 100++ but at the 60,70,80 even at 90 I've never noticed this problem..

Perhaps the combination,Height of the rider,type of the windshield,saddlebags,can cause this problem.

I have always the stock windshield with a Laminar Lip on and i never rode the bike with the saddlebags and the top box together.

Usually i use only the top box without the saddlebags on for every day use or for a weekend.

 

[Uncle Hud]

I think the "hole" in the air from the shield collapses (or starts to) around the top box causing the turbulence. The size, shape, adjustment level, etc. of the shield, and speed of course, has a bearing on the amount experienced. Your V Stream probably does contribute more due to a larger "hole" that is collapsing. A pillion bag or passenger acts to help streamline the collapse and push it back behind the box.I have an E55 and my CB 4x2 reverse flip shield causes a little wag at 75mph if I'm solo, so I only use it for long trips with my wife on back. No issues then.

From a physics standpoint, this certainly sounds reasonable. As the airstreams from the windshield converge behind the pilot, they would create buffeting at the front edge of the top box -- which would explain the wiggles.

Under 900gc's hypothesis, there would be five ways to mitigate:

(1) extend the convergence zone further aft (passenger, pillion bag, windshield adjustments, side wing-extensions for the windshield, and the like;

(2) push the 'leading edge' of the top box forward (passenger or pillion bag serve that purpose, too, as would some 'architectural' treatment to the top box);

(3) adjust speed to find the sweet spot where the convergence zone moves forward or aft of the top box;

(4) move the convergence zone forward (reduce the windshield size or eliminate the windshield; thinner pilot!); and

(5) remove the top box. (Hey, that would mitigate the wiggle.)

Since the wiggle is mostly side-to-side, I'd expect port-and-starboard airflow convergence is the primary cause, but over-the-top airflow may be a significant contributor.

Just thinking things through ...

Respectfully submitted,

Uncle Hud

 

[bigjohnsd]

I have a Givi 47. It is always on the bike a!ong with paniers.

I Always ride solo

I have not noticed this phemona well into xxx speeds with either the stock or yami touring windscreen.

May be because I'm a fairly big guy?

 

[Chiefblueman]

Stock top box, Calsci screen, bags. Riding solo and loaded pretty heavy I noticed a slight weave at indicated 130. Worse at 135, when I chopped throttle and sat up it got pretty scary.

I think the Calsci relieves the low pressure zone behind the screen a bit and may extend turbulence past the top box some. Eventually, it feels like the box catches enough air at high speed to make the front wheel light. Limited to short bursts to 120, bike remained solid. Traxxion Dynamics, Penske and new PR3s may have helped.

Hardly ever go that fast but in the middle of nowhere near Lusk, Wy I couldn't resist.

 

[audiowize]

Well, I increased the tire pressure to 40 front 42 rear, and this seemed to push the instability up beyond 100 MPH, which works for me!

I'll have to look for a decent looking seat bag to fill that space at some juncture.

 

[Just Krusen]

I had that wiggle on my '06 R1200RT with the trunk mounted. Wiggle got much better by bumping up the damping on the shock. Was easy to do with the ESA suspension and the results were immediate and very noticeable. I sold the trunk after 2 trips with it and was much happier without it.