Grand America Speed Limitation mis-information (re-post)
There is mis-information being circulated across this and other Forums that the Grand America speed is limited by BMW due to a known stability issue at high speed, which is not true. BMW didn't release the K16B GA for production knowing that it has high speed stability issues. BMW limits the speed on their K1600B Bagger/GA because of the Foot Boards.
If you read the Owners Manual, the reason for the speed limitation is because the Foot Boards do not have Shifter and Brake controls. They view this as a potential safety risk during high speed riding because the Rider has to re-position their feet under emergency situations, which could cause loss of control during very high speed maneuvering. That's why the GTL doesn't have that restriction....it doesn't come standard with Floor Boards.
As far as Grand America susceptibility to air turbulence, it's no different than any other large bike with a windshield and passenger trunk, (especially w/o a passenger). The more surface area the bike has the more it can be affected by air turbulence and cross winds. Did you ever ride a bike with a handlebar mounted wind screen.....lots of fun in high winds and especially behind Tractor Trailers. Throw in some Cross Winds, and you're in for a real treat.
If you're riding behind a Tractor Trailer on your Grand America and the air turbulence makes you nervous, you're in the wrong lane or too close to the Trailer, but you have the option of changing lanes, twist the throttle and say bye-bye.
I don't routinely ride at high speeds with my GA like I did with my Concours 1400, but I've ridden my Grand America to 100 mph a couple of times with no stability issues both in Cruise (soft suspension) mode and Road/Dynamic (stiffer suspension) mode. I'll admit, Road/Dynamic mode handles wind buffeting better than Cruise mode. Even my C14 wiggled behind Tractor Trailers and on windy days at high speeds. It's part of the riding experience. Also some Riders are more sensitive to bike feed back during turbulence than other riders. If it bothers you, slow down and ride at a speed that makes you comfortable. Better yet, get off the Interstate and do some back road curve carving. That's much more fun than riding behind Tractor Trailers.