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Discussion Starter #1 (Edited)
I've recently installed a Givi V46N top case on my '03 K12GT using the Givi F680 rack kit which replaces the factory luggage rack. I'm very pleased with the look and quality of the Givi case - plus the Suzuki 650 "Burgman Blue" cover is a PERFECT match to the BMW Orient Blue.

But there's a problem...

The bike is now VERY sensitive to turbulent air at highway speeds - like those found in the wake of an 18-wheeler. In turbulent air, the bike "wobbles" but sett;es down just fine in clear air. The problem is worse w/ a load in the case.

A few other details - I have a +4" Cee Bailey windscreen fitted and am running Metzeler Roadtec Z6 tires. There appears to be no appreciable difference in the "wobbles" with the screen in the low or high position. I never noticed the problem until fitting the Z6's in place of the OE Bridgestone Battleaxes, but that may be irrelevant - I put very few highway miles on the bike w/ the top case mounted running the Bridgestones.

Has anyone else experienced this problem? If so, have you found a fix?

I have some ideas about the cause, but would like to hear if anyone else has worked through this problem already. My theory is that the F680 mounting scheme has just enough flex to lead to a resonanant at a low enough frequency to upset the bike - the frequency gets lower as the case is loaded. I think the fix could be to stiffen up the mount by adding a third, stiff support from the front of the F680 rack to the BMW OE hoop that form the front portion of the stock luggage rack. This could raise the frequency to the point that the bike doesn't react.
 

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K12gt Wobble

I have the same setup that you have and yes my bike did the same thing with meztler Z4s. I don't know for sure but I think its a combination of the two add ons , remove one then try the interstate truck traffic. I switched to Conti Road Attack tires and although I haven't ridden on the interstate much I think the wobble may have lessened

Ron
 

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I have the same problem with my Givi 46 top case and I have Pilot road tires on my bike.
I thought it's my laminar lip so I took it off, but I have not been on the interstate since I took the lip off.
 

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I have V46 top case on bridgestone btx 020 and now pilot roads but have not noticed any change in stability.
 

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i rode my GT to the dealer for a tire change, about 20 miles of interstate, with my new bridgestones strapped on the back, i experienced the same turbulence symptoms. i'm thinking it is the effects of having something of that volume, that high up on the bike. just a thought.
 

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I did the same when I had my pilotroads mounted back in sept...only thing i noticed was the tires pressing in the middle of my back :) Take about strange looks as I passed folks by :)
 

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No problems with my Givi V46 .... but I stiffened the F680 brackets by adding small links to the indicators ... also mounted the bracket against the grab-hoop at the rear.... :rolleyes:
 

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Mark,
The problem is air turbulents from the truck crossing the bike in the wake of your pass. I have he same problem and it dosn't happen all the time. I don't know of a fix other than no bag. I get ready for it when I make a pass, so it dosn't bother me anymore. Every change I make to the bike has some sort of reaction in its performance.
 

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I have the V46, and have gone from Z4 to Z6 with no noticeable change.
I do notice, on my long trips when I put the sidecases on too, that I will get some buffeting when passing semi's. But not to be unexpected I think.
My setup is fairly rigid, but I did find that the bolts going down through the rack into the pivotable arms had loosened off. Check those out. The bolting under the seat was fine.
 

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blitzmann said:
I have the V46, and have gone from Z4 to Z6 with no noticeable change.
I do notice, on my long trips when I put the sidecases on too, that I will get some buffeting when passing semi's. But not to be unexpected I think.
My setup is fairly rigid, but I did find that the bolts going down through the rack into the pivotable arms had loosened off. Check those out. The bolting under the seat was fine.
Blitzmann,
Real good point on those pivotable arms.. CHECK THEM REGULARLY!! I have E52 and I carry tools back and forth to work.
 

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Mark,
I experience the same problem on my Triumph with the factory Givi top box in place. It is night and day with the box on and off. Interesting, though, is that the Chicane Mesa soft top box doesn't cause a problem on the K12GT - no instability at all.
 

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I have a E52N on a F680 rack mounted to my 2003 GT. I just bought the bike and my first ride on the freeway with the top case on really surprised me how unstable the front end was with the top case attached. The bike handles great without the top case mounted. I had a buddy behind me when riding the freeway with the empty topcase mounted and he said the case and mount were moving side to side ( buffeting ) alot in his opinion. I'm going to try to fasten the F680 rack to the rear rack to stiffen it up and see if that helps. It's so squirlly now I don't want to even ride it with the case on board.
 

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oscillation

Have you noticed a difference with a passenger and the topcase?
Maybe the bike's just balking back because of the way you made it look.
 

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The only time I use my Givi V46 is when the wife is riding pillion - she feels more comfortable with its backrest. In that case, I haven't noticed any wake turbulence instability that's significantly different than riding solo with just the factory sidecases.

Rusty
 

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RS and Givi

Well I have an RS. Black of course for speed purposes only. She's fitted with a 52 litre Givi top case, side bags, Road Attacks, and a comfort shield w/Laminar lip. All bikes will "dance" in the wake of a truck. Here's my remedy to eleminate the "dancing", with or without a trunk and/or bags. Rotate your right wrist in a downward motion and go like hell past the truck until you're in clean air, then resume a somewhat safe speed again. Works every time. I never maintain my current speed when passing a truck, not saying you do. I don't hang around trucks, especially during the hot months, been too close to one when a tire gave up the ghost. Talk about pucker!!
I have had my bike up to......well let's say 80+ with the Givi 52 in clean air and have no problems that I can remember because I'm totally concentrating on what's ahead. I feel though, the biggest air catcher is the side bags, lots of drag there. If anyone wants a stable ride in truck traffic, buy a KLT, that's the ultimate. With what we have, put on your dancin' shoes.
 

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cobbler said:
Here's my remedy to eleminate the "dancing", with or without a trunk and/or bags. Rotate your right wrist in a downward motion and go like hell past the truck until you're in clean air, then resume a somewhat safe speed again. Works every time. I never maintain my current speed when passing a truck, not saying you do. I don't hang around trucks, especially during the hot months, been too close to one when a tire gave up the ghost. Talk about pucker!!
.
Heard that man...Me too...I just don't hang around them. I've got a givi rack, but with a generic "Moto Details" topcase and have never had any instability issues more than I'd say are attributed to the truck next to me....Hell, semi sidedrafts even push my pickup around sometimes...I think it's just part of riding a bike on the interstate..

FWIW, mine has seen 140+ with both sidebags, topcase, rear seat bag, and tankbag without any problem....

Rich
 

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Some of you guys may have seen a post I placed late early this year. I had the BMW stock 28lt top case which sucked!!!

Lost credit cards, cheque book, in fact everything you dont want to see disappear down the road.

BMW replaced the faulty top case & yet I still was not relaxed. I saw numerous postings on this disappear about loss of Gt/RS BMW top cases, they simply fall off. Shocking to say the least.

I took the new top case back to my local dealer who refunded my money without question.

I bought a new Givi V46 without rack & bolted the carrier directly to the GT's rear rack with three stainless steel bolts. I opted not to use the Givi rack as I had one on my Boxer R1100S & after two months it broke on both sides near to a mounting point. I had it Mig welded & shortly afterwards traded the bike in with top & side cases.

Anyway, the new Givi is stable even when passing semi's etc...

Can take some photo's if anyone interested

Cheers
Craig
 

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cobbler said:
..been too close to one when a tire gave up the ghost. Talk about pucker!!
For all the traveling I've done, I've never seen a truck tire disintegrate in front of me. Seen a lot of evidence that it does happen tho.... :p
 
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