Bonneville America Forums Forums Technical Forums Accessories Windshield buffeting eliminated w modified lower

Several years ago, when we could still post pics on this website, I posted info and pics on my modified windshield lowers. The pics are long since gone, and I have since made the concept a little simpler, using just one flat Plexiglas plate, rather than two abutting plates.

Like many people, I had tried several windshields, trying to eliminate the buffeting. I solved this problem, and posted the info. In response to a recent post, I responded several times. This new posting is a consolidation of my replies, to make it easier for people this info in the future, if they do want to find this, on how to make your own windproof lowers system. Therefore, I may repeat myself a couple of times. Sorry.

I have a 2002 Bonneville America, and am 5 ft 10 in tall. Hope this helps someone.

The biggest (and cheapest) major improvement to a windshield is to stop the airflow underneath the headlight, which rises up over the gas tank, and causes turbulence. I use a standard Memphis Shades Alley Cat, with an extra 1/4 inch clear Plexiglas plate, mounted across and underneath the headlight, secured by Memphis Shades Lowers mounting kit # MEM9887. This plate is mounted to rise up and in front of the windshield, so that it passes all air up and over the windshield. I have been using it for years. There is absolutely no buffeting. There is a real "cone of silence" with no wind at all" for the rider. Also, since it is made of clear Plexiglas, it almost appears invisible on the bike.

The standard MS lowers don't quite do the same thing, since they do not block the airflow from coming under the headlight (and passing over the gas tank). That is the major source of the turbulence. To block it, you must make your own Plexiglas plate/air dam. It makes a world of difference, even over using the MS Lowers.

The Plexiglas flat plate extends between the brackets and UNDER the headlight. Actually, my Plexiglas flat plate only extends as wide as the lower part of my windshield, so if you don't look closely, it just looks like a long (low slung) windshield. The key to making it work though is to overlap the Plexiglas flat plate, so that it is in front of the lower edge of the windshield, thus forcing all the air upwards in front of and over the top of the windshield.

I tried making the plate wider and lower (longer), but it does not make any difference. To protect the knees, you would have to laterally add a piece of right angle (like angle iron) made of Plexiglas, to the bottom of the plate, to split the airflow and force it under the knees. However, I don’t know where to get “angle Plexiglas”. I guess I could just try to glue a one inch flange across/laterally to the bottom of the Plexiglas plate to accomplish that, but I just have not done it yet. Maybe I will try that before next winter, as I ride almost every day (commuting).

Lower Flat Plate-Side View
Lower Flat Plate-front view
Lower Flat Plate-front sideview

--Tom

Tom you outdid yourself with the writeup and pics. Huge thanks for all your effort and by golly I think I got the hang of what you're doing there. I'm gonna give that a bash for sure.

Happy wind-free riding!

Thanks for the update Thomas...might be useful in the tech vault?

What bullet lights are you running under your lower triple tree?

Driving lights are Optronics model QH-7CC, now available at Walmart for about $15 for the PAIR, including the wiring. These are 55watts each, and give a very bright (but yelowish rather than bluish) light. These are chromed METAL, and the brackets fit perfectly, being bolted into the existing holes for the Triumph Windshield mounting bars. I originally used the Triumph driving light wiring harness and a small toggle switch, to be able to switch them on and off at the tank console, but that is not necessary at all. I now leave them on continuously (for the last couple of years). These have shown no wear, or rust, and the bulbs are still just fine. (My bike is kept in a garage.) If I had to do it again, I would not install a switch for them. Just wire them into the Triumph 10 Amp fuse (fusebox) for driving lights. Also, the other Optronics light kits do not fit (at least not back then). --Tom

Problem solved when I put on a Windvest 14" that was originally intended for a H-D. I modified the hardware for my narrower bars and found this to practically eliminate the wind. I also invested in a new full face modular helmet which made quite a difference as well. The biggest difference though was because of the Windvest. Not cheap, but makes for a much better ride.

Whatever you do, don't leave your key on without the bike running. Those always-on cheapo fog lights will drain your battery post haste. Ask me how I know.

Tom...was the biggest difference extending the shield lower (making it longer) or closing up the area surrounding the headlight?

Who's Mike?

dunno what your talking about.

Thanks for your idea!

The big difference is closing off the airflow under the headlight, which then proceeds up over the top of the tank. Of course, I did not do that without making it as wide as the bottom of the windshield. However, a few facts of history, from previous trial and error testing of this concept:
1. Making the flat plate wider than the bottom of the windshield did not help anything, not even protecting the knees more.
2. Using the original lowers, even very long lowers, did not help anything, not even protecting the knees more. They are not nearly as good, because they did not stop airflow coming from under the headlight.
3. The only future improvement that I can imagine now, is to glue a strip of the same 1/4 inch thick Plexiglass (by its edge) laterally to and extending the width of the bottom of the main flat plate. It would be about 1 inch front to back. That right angle edge should function to split any remaining air that would have otherwised come up behind the windshield. With that right angle edge, the air should be parted/split, with some going up in front of the windshield, and some being forced downward by the " > " edge (like the front of an airplane wing). That should reduce airflow on the knees in the winter, and come winter I will probably try that. Hope this helps, --Tom

Tom,
Your certianly onto something here. I went to the local Home Depot and got some plexi, madea quick panel to cover the opening around the headlight (it wasnt perfect and still left some gap). I didnt go as low as you did (I have a light bar) BUT the result was interesting to say the least. Ill post a pic later this morning.

I did a test run on the hwy and got up to 80/90. I still had some buffeting at higher speeds BUT it was significantly reduced at legal speeds.
Im going to go out and do some direct comparison one day this week and report back.

Tom, Thank you for the time and effort youve put into this and then sharing with everyone!

********** as promised...pictures of my attempt at Toms mod:
before


after (the protective plastic is still on the plexi), you can see some of the gap thats still left over). I fastened it by allowing it to rest between the light bar and lower yoke, I used a couple zip ties at teh top to hold it to the forks.


I think, per Toms observations, I need to close up some of the gap around the light and maybe add a small peice under the light bar to eliminate what seems to be the remainder of the buffeting.


Ill say it again...without Toms post I never would have thought of this as being the cause/cure for the buffeting.
Thanks for sharing!