Renters and owners of the BMW F800GS everywhere are asking the same question and not realizing, it's probably the wind hitting your shoulders! The next time you ride, make a concerted effort to pay attention to sensations in your upper arms, across your chest, and into your shoulders. Slipping around the windshield and pulsing back and forth on both sides, the buffeting wind is likely the reason for that shaking on the F800GS. (Riders typically notice this on straight sections, over 60mph.)
Surely the F800GS isn't the first bike to have aerodynamic issues like this, and it won't be the last. Why do some bikes shake like this then and others don't? Keep in mind a few key factors in motorcycle aerodynamics, and you'll see it's not easy to answer:
How all of this ties into the "rake" and changing trail measurements of the motorcycle's front end as we cover different terrain is part of why some bikes feel "shakier" than others. Of course we can never rule out that you've had a dented or damaged front wheel (especially on the F800GS which is known for having soft, easily damaged rims.) Still, this article is meant to remind motorcycle riders that many factors go into the aerodynamics of your motorcycles, and your particular set of factors might be the cause of unexpected sensations. Pay close attention to everything while you're riding, and don't just jump to conclusions. It's highly unlikely that BMW Motorrad would design a motorcycle that "shakes" over 60mph, right?