Aerodynamics of naked bike buffeting
Posted: Sat Apr 14, 2007 11:13 am
When I got my RF1000 helmet, I noticed that placing my hand to block the opening near the chin reduced the wind noise considerably. Knowing that some R1150GS riders often put small saddle bags on both sides of their gas tank to prevent wind from this area of the bike from sweeping upward toward their heads, I fully realized that the primary reason we get buffeting on our Roadsters (if equipped with the touring shield) is not because of non-laminar flow coming off the top of the shield, but rather the wind sweeping upward from below the shield toward our helmets.
A week ago, I bought a HD touring shield for my Dyna Super Glide Sport. Riding down the highway at 75 mph, I was disappointed that there seemed to be rather severe buffeting despite the size of the shield. I tried blocking the gap again between my chin and helmet but doing so only cut down on the noise by about half. I then placed my left forearm horizontally across my abdomen to block the wind sweeping upward and sure enough, this reduced the wind noise completely! The only thing I could hear was the thrumming of the v-twin. Knowing also that there are optional lower deflector panels on Gold Wings, FJRs, and even the HD Road Glide, I did a search of the Internet. I found lower deflector panels from National Cycle for Harleys, but these are only compatible with the National Cycle touring shield. I’m continuing my search for lower deflector shields for my Dyna, and am looking for ones that are compatible for R1150Rs.
The long and the short of it is that larger windshields create low pressure behind them. Air passing the edge of the shield then flows inward behind the shield due to the lower pressure. It is this airflow that creates buffeting and wind noise. The reason wind sweeps upward from the bottom rather than the top is because of the angle of the windshield, i.e. – the bottom part of the shield is further forward than the top part of the shield. We thus have to find a way to prevent this stream of air from coming toward our heads. Lower deflector shields seem to be the answer judging from the prevalence of these things. But I have not been able to find any for the R1150R.
A week ago, I bought a HD touring shield for my Dyna Super Glide Sport. Riding down the highway at 75 mph, I was disappointed that there seemed to be rather severe buffeting despite the size of the shield. I tried blocking the gap again between my chin and helmet but doing so only cut down on the noise by about half. I then placed my left forearm horizontally across my abdomen to block the wind sweeping upward and sure enough, this reduced the wind noise completely! The only thing I could hear was the thrumming of the v-twin. Knowing also that there are optional lower deflector panels on Gold Wings, FJRs, and even the HD Road Glide, I did a search of the Internet. I found lower deflector panels from National Cycle for Harleys, but these are only compatible with the National Cycle touring shield. I’m continuing my search for lower deflector shields for my Dyna, and am looking for ones that are compatible for R1150Rs.
The long and the short of it is that larger windshields create low pressure behind them. Air passing the edge of the shield then flows inward behind the shield due to the lower pressure. It is this airflow that creates buffeting and wind noise. The reason wind sweeps upward from the bottom rather than the top is because of the angle of the windshield, i.e. – the bottom part of the shield is further forward than the top part of the shield. We thus have to find a way to prevent this stream of air from coming toward our heads. Lower deflector shields seem to be the answer judging from the prevalence of these things. But I have not been able to find any for the R1150R.
