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There's nothing wrong with the aerodynamics of the K bikes. The major issue at highway speeds in and around large vehicles is the bike's weight. At 730 LBS this is not a heavy 880 LBS HD and it's going to tend to get pushed around in dirty air and cross winds. I always keep at least 3 car lengths in front of me and I never let any vehicle stay beside me for more than a few seconds. When the I get into dirty air I just lighten up my grip and let the bike do what it wants just making small corrections to keep it in the lane. Most of the time I have the CC on and my hands are just resting on the grips usually only my right hand in on top of the grip my left hand is holding a cig. I don't have any problems handing this bike in any condition. My suggestion is go to a riding course and learn how to ride. I'm not saying this to be rude but if you sit back and think about it how many of you actually know what the capabilities of the K bike are. Anyone can negotiate a straight line ................
I agree that there's nothing wrong with the aerodynamics of the K bikes. Simple riding techniques solve most problems.

I don't think being pushed around is a weight issue though. I do a lot of 2-up riding on my GTL, and the extra heft doesn't make much difference. My previous K1200LT, which was at least 85lbs heavier, got pushed around too. 1-up or 2-up -- it didn't make a difference. I'm guessing it has more to do with the K16 bikes sitting you up higher than a big Harley type motorcycle. At least that's my best guess.
 

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My suggestion is go to a riding course and learn how to ride. I'm not saying this to be rude
Well, actually you are :censored:

The op has asked about a well known and documented effect which is acknowledged by BMW by limiting the GAs speed to just over 100mph - unlike the bagger - about 130mph I believe, or the GT/GTL - unrestricted at 150mph+ so doing a course will not have any actual effect on the bike, and not many courses will teach you about 80/90mph highway riding, because as you say:

Anyone can negotiate a straight line ................
This is about the feel of the bike, not how good a rider you are.

James
 

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Okay cut to the chase here. The so-called instability has been present on all 4 of my GTL's since the first one that I bought when they were introduced. Tires and tire condition seems to play a major role in this issue. I have found that I have a natural tendency to "tighten up" on the handlebar grips when I feel the bike move around in dirty air, especially when I haven't ridden the bike for a while. Once I feel the perceived instability start, I have to remind my self to relax on the grips and just like magic things improve. I am not saying the instability goes away completely, but it is always much improved. We are after all creatures of habit and when we perceive something isn't right in a stressful situation, we automatically react in an almost predetermined way, usually by tensing up our muscles which almost always makes things worse. Convince yourself to lighten up on the grips and let the big girl calm down a bit. She may still move around a little, but nothing like when you have a death grip on the handlebars. And don't forget to keep an eye on your tires!
Rick H.
 

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I honestly think that taking off the floor boards will help with instability at high speeds but not necessarily buffeting from larger vehicles.
When you say you are running your tires at max air pressure, what would that pressure be?
 
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My GTL was a bit twitchy until I installed a Z-technic windshield and put a sloped tail bag on the passenger seat in front of the top box. Buffeting gone.
 

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Next time you hit dirty air and the bike starts to do the two step, lower your windshield to the bottom and see what happens. Its more air on the helmet and upper body but when its hot.. its helps cool you down some.

My GTL when on the slab and around heavy traffic wether it be cars or trucks I lower my windshield and it definatly helps settle the front end down in the dirty air. Its not perfect but it helps. Its my belief that the angle of the windshield makes a difference, maybe decreasing the angle provides more down force on the front end and or makes the entire front of the bike more aerodynamic... **** I dont know but it kinda makes sense to me.

FWIW I dont think its a weight issue either. My 12 Road Glide Ultra was a heavy pig and it still moved around some in the dirty air. At the end of the day I figure its all part of the motorcycling experience.
 

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FWIW I dont think its a weight issue either. My 12 Road Glide Ultra was a heavy pig and it still moved around some in the dirty air. At the end of the day I figure its all part of the motorcycling experience.
Well said. If it was a weight issue, monstrous big-rigs on the 210 Freeway in SoCal wouldn't get blown over by Santa Ana winds. The K16s might move around a bit more than pig Harleys, but nothing you do to the bike is going to make a big difference. It is all part of the motorcycling experience. Embrace it and ride on.
 

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Well said. If it was a weight issue, monstrous big-rigs on the 210 Freeway in SoCal wouldn't get blown over by Santa Ana winds. The K16s might move around a bit more than pig Harleys, but nothing you do to the bike is going to make a big difference. It is all part of the motorcycling experience. Embrace it and ride on.
It is a weight issue. But it is also a surface area issue. Sails on sailboats are one extreme while a lead brick would be the opposite. But trucks have a large surface area on their sides so they're very susceptible to cross winds. Changing the shape or size of the surface catching the wind will certainly have an impact. I've venture to say that bikes with a small GT windscreen all the way down and not cases mounted would be noticably less impacted GTLs with oversized screens all the way up, with Aerowings mounted, and all the cases installed.
 

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@RefCat, if you’re on a K16 with 70-100 mph Santa Ana cross winds blowing horizontally against you, it doesn’t matter what windshield, topcase, or tires you’re running.

Ask me how I know. 😊
 

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@RefCat, if you’re on a K16 with 70-100 mph Santa Ana cross winds blowing horizontally against you, it doesn’t matter what windshield, topcase, or tires you’re running.

Ask me how I know. 😊
If you're on a K1600 with 70-100 cross winds, you're not very likely to remain on that K1600 very long.

I was on a trip last year with strong cross winds...2-up and pulling a unigo trailer. I was probably riding with what felt like a 10 degree lean for over an hour straight. It was funny because whenever I crossed a bridge, the barriers would block enough of the wind that I'd be straight up for 100 ft. then back to the lean.
 

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If you're on a K1600 with 70-100 cross winds, you're not very likely to remain on that K1600 very long.
It’s not something I search out, but sometimes you get caught up in it. Its part of living in the foothills of SoCal during wind season. You learn how to ride through it. Make yourself small and anticipate. It’s why I don’t have a lot of patience with riders complaining about far less turbulence.
 

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There's nothing wrong with the aerodynamics of the K bikes. The major issue at highway speeds in and around large vehicles is the bike's weight. At 730 LBS this is not a heavy 880 LBS HD and it's going to tend to get pushed around in dirty air and cross winds. I always keep at least 3 car lengths in front of me and I never let any vehicle stay beside me for more than a few seconds. When the I get into dirty air I just lighten up my grip and let the bike do what it wants just making small corrections to keep it in the lane. Most of the time I have the CC on and my hands are just resting on the grips usually only my right hand in on top of the grip my left hand is holding a cig. I don't have any problems handing this bike in any condition. My suggestion is go to a riding course and learn how to ride. I'm not saying this to be rude but if you sit back and think about it how many of you actually know what the capabilities of the K bike are. Anyone can negotiate a straight line ................
Thinking out loud..

The aerodynamics have a lot to do with the stability but not in an intuitive way - but the geometry of the bike is also a big factor.. The large frontal area and relatively high cross section coupled with the sport oriented design goals are going to make the bike more agile (less stable) by design. I say that because wind protection, aesthetics, and comfort, and being nimble (for a big bike) all come with trade-offs. Its not about weight (which is the intuitive answer), its about aerodynamics and suspension design. A lead arrow will move through dirty air better than a paper shoebox. The large frontal area of the bike is going to create turbulence at the rear of the bike. It will also act as a lever when you encounter the turbulence coming from the vehicle in front of you. The frontal cross section must cut through the wind but not all forces are coming from directly ahead. Whenever the pressure is coming from the sides, like when you encounter turbulence (dirty air) from the truck in front of you the whole thing acts more like a sail than a knife. From a side profile the K1600 is a relatively solid sheet and the high placement of bags means that it is going to catch more air. From a side profile an HD is lower and more open. From a purely aero perspective the K1600 has many advantages in a straight line and moderately dirty air while the HD has its own disadvantages in the same situation. When it comes to pure turbulence, its all a series of trade-offs.

Anecdotal evidence (cures) such as lowering the windshield, a passenger or something to fill the gap between rider and top box, fewer complaints from GT riders (weight position, rider position) are all evidence that independent of weight, improving aero improves handling characteristics.

Couple this together with the design goal of creating a more sport oriented super tourer and you have the other decisions that effect stability. The K1600 has about 4" of trail vs the HD (ultra limited) which has about 6" of trail. Trail is the distance between the center line drawn from the top of the forks to the ground and a line drawn vertically through the front axle to the ground. The distance between these two lines is the bikes 'trail' as the actual tire contact is behind the line projected by the forks. The design decision around less trail means that the K1600 which be much more agile into corners always but at the expense of absolute stability. The K1600 trail selection is considered to be ideal btw. The HD design is all about stability while giving up cornering agility and that decision is considered to be sluggish (especially coupled with a larger tire). Then you have the gyro effect of a larger tire as well.

Those two factors (aero and geometry) will have more impact on stability than weight.

Just an observation to consider when it comes to the design decisions of the k-bikes and those trade-offs.

1. Trucks in Europe are smaller, sometimes a lot smaller in comparison to their US counterparts.
2. Those trucks drive slower (ironically) and they tend to caravan often and have great lane control.

In the US you have large trucks passing large trucks, while speeding, and almost zero lane control. That is the worst case scenario for turbulence. I don't know if this is a factor in the German design mindset but its a reality that North Americans have to deal with on the slab.
 

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^^^Well said. Bottom line; side surface area results in more turbulence induced buffeting (lateral motions). I highly doubt any appreciable lift is generated, except via the previously mentioned floorboards at high speeds, and thus the “weight on wheels” remains safe when riding in amongst traffic. Whenever possible, move away from traffic and get to the front; which is good riding for a number of reasons. My greatest fear is having an encounter with a large piece of rubber tread we all see scattering the shoulder of every highway. Being in front allows for avoidance - being beside a semi trailer when one of those re-treads lets go could be deadly.
 

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My greatest fear is having an encounter with a large piece of rubber tread we all see scattering the shoulder of every highway. Being in front allows for avoidance - being beside a semi trailer when one of those re-treads lets go could be deadly.
Yup. Had it happen to me in a rental car many years ago - Came straight out from the side of the truck and broadsided my car. Scared the s**t out of me and I was well protected. Put a big dent and lots of scratches in the car.

All kinds of crap (not just rubber) can also come off the back of them: Steel lever bars for tightening down their load straps are very common. Also bungees, wood blocks, etc.. Not to mention the crap they will pick up from the roads. I stay the h**l away from anything pulling a trailer or anything with something on top or in the back of it. It still amazes me every time I see a full extension ladder laying on the interstate and no one knew it was missing or bothered to stop to pick it up.
 

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Preface: I love the bike and can live with it as I don't do much multi-lane highway riding. I have 4 bikes in the garage atm and none of them aside from the B behave as badly in dirty air. I recently took a 600+ mile day trip and had more than a few pucker moments from dirty air being near trucks on the highway. My buddy noticed me getting out of shape without me mentioning the issue. To be fair the pace was brisk at times. I had to close my air deflectors which seemed to help. My B is unstable at speed in dirty air - period.

Go easy on the people who complain.
 

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I'd like to believe that BMW Motorrad spent time and money in a wind tunnel testing the airflow around our bikes, trying to get the best cleanest flow they could. That said I think most after market "fixes" are going to fail. My solution usually involves passing a truck as fast as possible.
I disagree. Bike was designed as gtl/gt. Adding changes for the B and GA are an afterthought like putting a Lincoln nameplate on a Ford. Doubt there was much additional texting for the afterthought models. But neither of us know for sure - we are both guessing.
 
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Preface: I love the bike and can live with it as I don't do much multi-lane highway riding. I have 4 bikes in the garage atm and none of them aside from the B behave as badly in dirty air. I recently took a 600+ mile day trip and had more than a few pucker moments from dirty air being near trucks on the highway. My buddy noticed me getting out of shape without me mentioning the issue. To be fair the pace was brisk at times. I had to close my air deflectors which seemed to help. My B is unstable at speed in dirty air - period.

Go easy on the people who complain.
The one piece of advice is to loosen up the grip. The bike has two very large gyroscopes that want to keep you upright and moving straight. I just let the bike wiggle and it settles right down, then shoulder check, hit the blinky button, twist the grin management system in your right hand. life is good.
 
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