something needs to be separated out here
head buffeting is when the laminar hi speed flow of air coming off the top of the windshield does not make it up and over your helmet before it goes chaotic and turbulent. You cannot see it in air, but in a river its like the smooth flow of water over a large round rock. It stays laminar about halfway across the rock, then it goes turbulent and become white water foam.
If you helmet is touching that white water equal in the air, its like your helmet is in a paint shaker, you eyes are wobbling like jello, you cant read road signs, and your brain is hitting the inside of your skull. That is head buffeting. It normally does not happen below 60...65mph of windspeed.
The fix for head buffeting is almost always to get the air flow off the edge of the windshield thrown up and over your helmet before it collapses into turbulence. Putting fork deflectors on does this by giving the air more of a running start up and over the windshield.
I know there is a lot of discussion about air coming up around the gas tank, but that is not going to cause the air off the top of the windshield to become turbulent. The air you are feeling behind the windshield and around the gas tank and air intake is just a draft. Put your hand over the top of the windshield edge and feel the difference in the wind blast coming across.
I have a Memphis Shades Fats and fork deflectors on my 650. I can ride at 80mph with no buffeting, but its not quiet, and its not a still pocket of air. On a hot sunny day I have to stick my knees out to get some airflow over my chest or Im stewing in my own juices - but again that is just creating a draft across my body, it does not create head buffeting at highway speeds.
If you really want to sit in a still pocket of air at 85mph you need a fully faired motorcycle, like a goldwing or an SVTC, or an FJR1300. Batwings are better than classic police bike style windshields for head buffeting, but there is a reason that Goldwings and SVTCs have full fairings. If that is the kind of ride you want, that is what you need.
you can spend a lot of time and money to make your batwing look like a Goldwing in functionality, and still not be happy with the results. To design this kind of stuff you need a windtunnel.
Last edited by KCW; 09-18-2019 at 09:07 AM.