Windshield back pressure

[Redeye]

Been reading the thread on the CalSci windshield update and noted the comment on back pressure.

Has anyone found a farkle to relieve this problem on any screen. I'm new to the ST and first time I raised the screen I thought I had a pillion on back giving me a push :eek: . Do any of the fairing/mirror deflector kits help, or is it just something that we have to get used to? It's a very strange sensation and I would imagine tiring on a long ride with it pushing you towards the bars.

[Keith_UK]

REDEYE - We Brits have a great option, which is the Flip Top windshield from the UK supplier 'Bike-Quip', based in Camberley, Surrey.

This longstanding debate regarding after market screen options is widely shared on both sides of the Pond. I suggest that you consider the discussion(s) posted on the following thread [on another forum]: Link=

http://groups.msn.com/ST1300US/general.msnw?action=get_message&mview=0&ID_Message=63262&LastModified=4675528568078761023

I have the 1" taller and 2" wider version of the Flip Top, which you can acquire from Keith Munro (Bike-Quip's proprietor) for just £75 including P&P.

I recommend this product - getting it was one of my better after-market buying decisions.

Good luck. I hope you solve your back-pressure problem, which incidentally, I have never experienced either with the original stock screen -or- my new Flip Top replacement screen.

Regards

KEITH (in Cornwall)

[STArnie13]

I have never noticed that problem on my ST1300 standard with the shield at the highest setting. I have put in one 900 mile day with no problems on it.

I used to think that people were crazy when they talked about back pressure.
That was until I felt it on my K1200LT. I raised the shield on it to the top and I felt a change on my back so I now know that it does exist. It probably just affects people differently. That being the case there may be many different solutions. I hope that you find a good one for you. :03biker:

[Danny Sanders]

Try using a vent in the screen to help alleviate the back pressure/turbulence behind the windshield. That and Baker wind wings helped a bunch when I rode my Goldwing.

[Pred8tor]

I don't notice it, either. I wonder if this is a "size of the rider" issue? I'm just over 5 ft. 8 inches - with stock windshield and bars. Does it affect taller or shorter riders? With stock bars or risers? They are the only variables I can think of - unless some are more sensitive that others.

[Carl_T]

This is one I do have. Definite back pressure all the way up and near the top. What I would like to reduce is the passenger wind buffeting. My wife reports her helmet lifting with the windshield down (could be helmet brand) and so we always ride with it up, no breeze in summer and back pressure on me. The back pressure is small though, but there. 5' 9"

[Jeff F]

Good info here ....

http://www.st-owners.com/forums/showthread.php?t=2756&highlight=windshield

[Jeff F]

... and here.

http://www.st-owners.com/forums/showthread.php?t=4207&highlight=windshield

[NormanPCN]

This link (http://www.st-owners.com/forums/showthread.php?t=3474) shows another shape to enlarge the bottom vent. More like the stock vent shape.

[Redeye]

REDEYE - We Brits have a great option, which is the Flip Top windshield from the UK supplier 'Bike-Quip', based in Camberley, Surrey.

Regards

KEITH (in Cornwall)

What difference did the fliptop make over the standard screen?

[04ST1300a]

The under mirror deflectors do help.
To all those who ordered a set (or 2)
I should be able to ship this week, thanks.
Sorry for the wait, been out of town and behind at work.... :04biker:

.

[stuey]

Hi guys,

I suffered this back pressure thing, I'm 6'3" by the way, and as said previously it was like doing push ups.
I decided to go down the route of altering the angle of the screen. I believe Rifle do "Tuning Blocks" to achieve this, but I couldn't find anyone in the UK that sells these so I did a temporary fix that cost NOTHING.
If you look behind your screen you have an angled piece of steel which the screen bolts to. If you remove the nuts which secure this to the inner bracket, you can lower the angle of the screen but the bottom nut will only pinch the bracket with half its width, whilst the top nut gets a full grip. This seems to be fine and I've done 2000 miles like this with no ill efects.
The result of lowering the angle is that you increase the gap between the bottom edge of the screen and the dash, allowing far more air up the back of the screen. This works a treat, with all the back pressure gone and the wife reports far less buffeting to her helmet. I am now planning on either getting some tuning blocks, or making something similar, possibly something that is adjustable as far as screen angle goes.

hope this helps

Stu

[Kempo-STer]

I have experienced the back pressure on my helmet. In its highest position yes it felt like someone had their hand on the back of my helmet pushing forward.
I am 5' 11''.

My first ergonomical chnage that I am coming to a slow realization on is handlebar risers..I will change my positioning to be a little more upright then re-evaluate the windshield..

Todd

[Keith_UK]

REDEYE - In answer to your question: The outward flip towards the top of the screen redirects the windblast right over both the rider's and pillion's helmets - there is no question about this.

Remember that, IMHO, it is not necessarily the screen per se that causes the noise or the buffeting. These irritating effects are simply unwanted bi-products, which are created by the wind blasting around your helmet(s).

Logic dictates that if the windblast is deflected over your lid(s), then your riding is bound to go quiet and become more comfortable as a result.
I can honestly say that: (1) riding with the Flip Top in its lowest position is a real breeze (no pun intended!) up to speeds of 75 - 80 mph; (2) raise the top of the screen up to just below eye level and then speeds of 100+ mph can still easily be tolerated; (3) with the screen fully raised so you look through it, then it's like being sat behind a transparent barn door - in other words, total comfort.

The only minor downside with the Flip Top is where the flip feature starts to bend outwards towards the top of the screen. There is a definite and very noticeable distortion in this area, which is about 2" in depth right across the width of the screen. But I simply don't notice this anymore; it 'virtually' disappears, well it does for me anyway, within 30 seconds of every rideout.

If you want to further discuss the Flip Top's features, then give Keith Munro a call on 01252 835681. He's most helpful, honest and open-handed; a very obliging fellow indeed.

Good luck.

KEITH

[2005c6]

I have nothing to add, but I have read many posts on this and "the other" ST1300 forum, and this is by far the most helpful thread on the subject.

Just wanted to say thanks! :04biker:

[Fireball18]

If I remember my aerodynamics correctly, something like this happens with the windshield: Going through the air the curved windshield cuts through much the same as the wing of an airplane, parting the air which flows to either side. Unlike a wing which has a solid surface that is relatively flat on the bottom and curved on the top producing differing pressures causing "lift," the windshield ends at its edges. The result is a vacuum of sorts behind the windshield. The rider sits right at that point. The wind moves around the windshield and at some point, determined by the shape and slope of the windshield, breaks inward toward the "vacuum" behind it. Unfortunately for the rider, he/she is sitting right where the wind breaks forward, resulting in the wind pushing the rider forward. This, of course, is uncomfortable.

Enter windshield design. Adding a larger lower vent area at the bottom of the shield increases the airflow up the inside surface, hopefully reducing the backdrafting effect. Cutting surface vents, such as in the Clearview shield or the front vent on the Cee Bailey shield actually cause air to come straight in, opposing backdrafting to some degree.

As long as there is a windshield, the backdrafting will occur, regardless of windshield shape, size or angle. The best that can be hoped for to reduce the backdraft using windshield shape and/or angle. Tulsa 9 (and others) have been successful in doing this by making a windshield that is so tall that the upper lip come over and past the rider's head, extending the backdrafting considerably to the rear, providing for greater rider and passenger comfort. On the downside, such a setup is pretty darn hot when the temperatures soar. One can get side wings to add to the center width of the windshield (available for about $40.00 a pair from J.C. Whitney, for example) that serve to push the air farther out to the sides. Still, it will eventually close around behind the rider. You just can't get away from it entirely unless you have NO windshield or ride with it all the way down.

Keep working on it guys. Someone may eventually create the whiz-bang windshield that will solve our backdrafting problem.

[gene]

Guys I just put a Clearveiw GT on my ride and wife loves it. Backpressure is greatly reduced and wife says turbulance is gone. She can now look to the side past me without being knocked around . Clearveiw shields are made with the flip at the top of shield, there is no distortion at the top and cearity is great. Buffeting on me is now gone as well as almost all wind noise in helmet. Only thing is with cat eye vents noise is the sme as stock I tried shield with vents and buffeting was gone but noise was the same . Returned it for a non-vented unit and it is great. Also customer service is fantastic. Call John he will help you out 303-838-0886 or 1-800-798-6089








Honda ST1300 GT
Clearview Shields has just completed their new ST1300 GT screen. It is currently available in three heights, Stock height, GT Small (1" vertically taller than stock height but 3" wider), GT Medium (2" vertically taller than stock and 3" wider than stock). GT screens incorporate a re-curved section on top for improved lift of the airflow for the rider and passenger.



HON-S3GS Stock height GT replacement Gray.


HON-S300 ST1300 STOCK $147.29
HON-S30S ST1300 GT SMALL $157.29
HON-S30M ST1300 GT MEDIUM $157.29
HON-S30L ST1300 GT Large $157.29
LT GRAY TINT ADDITIONAL $20.00

New For 2005

Pressure relief vents to decrease back pressure.


PRV slots
These pressure relief slots are designed to aid in reducing low pressure behind our GT windshields.
Slots are located low and to the left and right of the center vent. Black trim optional.



ACC-PRVTRIM (SET OF 2) $25.00


Ordering
We ship out UPS ground and can priority mail for additional $18.00 to any destination within the
contiguous USA.Express mail shipments are also available please inquire for a quote.
COD's shipments can be made with either carrier within the US for $7.50

When inquiring on proper height recommendation please remember to include your overall body height
along with your inseam. Also specify the type of seat and/or if you ride with a passenger more than 50% of the time.

When ordering please include your name, address, ship to address, a daytime phone, credit card #, and/or email address. Clearview Shields will respond to your inquiry within 24 hours inside any business day.

We accept Visa, MasterCard, American Express, and Discover

To Order contact:

Craig Stenger
Sales / Technical information
Clearview Shields
info@clearviewshields.com
www.clearviewshields.com
Phone:303 838 0886
Toll Free: 800 798 6089
Fax: 303 838 6894


Terms and conditions
Each Clearview Shields Product is packaged with an unique clear 2ml film that adheres and conforms to the windshields front and back surfaces. This allows the rider to fully install the screen, inspect it for fit, and test drive it for performance (given the rider can look over the windshield). If upon the completion of the evaluation the rider feels they need to make a change or is not satisfied with the product, the rider may exchange it for a different height or return it for a full refund, as long as the packaging has not been removed. The rider has 30 days from the product ship date to decide. If the packaging has been removed or damaged in any part of the screen (excluding holes made for the mounting of the windshield) then the terms of this agreement will be voided, and no return or exchange will be allowed.

Warranty
Clearview Shields covers all windshield products against defects in the material or workmanship for 1 year from the date of purchase by an original consumer purchaser. Clearview Shields acknowledges no other warranties, either expressed or implied.











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[sportridervince]

Gene ... does your new shield have the SEvent in the center? You didn't mention what size you went for I'm just wondering how the wider screen is for clearance around the mirrors especially if you are using the Honda mirror deflectors.

vince

[AZST]

Is backpressure the reason I find smushed bugs on the inside of the glass sometimes?? This has always baffled me.

--Bryan
04ST1300A
STOC# 5197
:04biker:

[NormanPCN]

If I remember my aerodynamics correctly, something like this happens with the windshield:

Even simpler. Wind blows from high pressure to low pressure areas. The shield punches a "hole" in the air. This makes less air behind the shield and therefore lower air pressure. The air surrounding the bike has higher pressure and guess where it is going to want to go. This low pressure is also why the front end of the bike can feel lighter at high speeds. Low pressure behind the shield and higher pressure under the bike = lift. The very instant the air leaves the edge of the shield it is trying to turn into the low pressure area. The greater the pressure differential the harder the turn. The harder the air tries to turn = stronger turbulence/buffeting.

Reducing the low pressure has multiple benificial effects.
less turbulence, less lift, less drag, less backpressure(tailwind)
You can never get rid of any of these things. Turbulence you can move to a different position by using a bigger/smaller windshield.

[gene]

SPORTRIDERVINCE my shield is a GT-medium they don't have center vents. I don't have mirror deflecors but there should be plenty of room. If I were to do it again Iwould purchase both a GT-small with vents and without vents and return one after trying both ,they are great to work with.

[John Anthony]

Like Gene, I installed a Clearview GT Small with the pressure relief vent. Took it out for a nice test ride today and couldn't be happier. Turbulence and back pressure are gone. I like to ride with my windshield as low as possible and the up curve on the Clearview does a nice job of displacing air up over my helmet.

On a scale of 1-10, I'd give this one a solid 9.

John

[tinfish81]

Has anyone tried a Laminar Lip? I know they worked well on the ST100 but I haven't heard reports on their effectiveness on the ST13.

[ilvtoride]

Gene, do you have pictures you can post? I went on to the site and they had no pictures of our ride. Pictures looking through the screen from the rider4s perspective woould be great if you can. :confused:


Does any one else have these screens?

The advertisement looks great.. :bow1: ..But onle we know for sure...

Thanks for your posting Gene.

[Rob (from Hoosierville)]

Has anyone just tried spacing the shield out further from the fairing? In other words inserting some spacers (I'm going to start at about 1") between the brackets and the windshield. This would approximate the spacing of the Windbender shield I had on my GL1800. That shield flat worked. The folks at Rifle shields use a similar spacer they call a "Tuning Block" that also changes the angle of the shield.

The benefit here is that more air will be allowed to come under the shield and soften the low pressure area behind it. The transitional areas between low and high are what create buffeting (as the high/low pressure transition area collapses) and the feeling you are getting pushed into the bars. The phenomenon is caused by your back acting as a barrier between the high and low pressure zone, and the differential is literally trying to suck you into the area behind the shield.

The whole thing is easier to comprehend if you lose the mindset we all grew up with. Wind does not blow, it sucks. Airflow is induced through pressure differential, with low pressure pulling air from high pressure. Anything you can do to soften the transition from low to high will smooth things out in a big way. Over the next few weeks I'll be working on some spacers and find out what works best. Anyone who's been down the same path please chime in.

[Redeye]

Just had a look at the Clearview website. Not exactly overflowing with information. ST1300 not even listed!

Or am I missing something?

[Carl_T]

I see them for sale and listed here, not pics though.

Clearview for ST1300 (http://www.sporttouringusa.com/www/clearview.htm)

[stuey]

Has anyone just tried spacing the shield out further from the fairing? In other words inserting some spacers (I'm going to start at about 1") between the brackets and the windshield. This would approximate the spacing of the Windbender shield I had on my GL1800. That shield flat worked. The folks at Rifle shields use a similar spacer they call a "Tuning Block" that also changes the angle of the shield.

The benefit here is that more air will be allowed to come under the shield and soften the low pressure area behind it. The transitional areas between low and high are what create buffeting (as the high/low pressure transition area collapses) and the feeling you are getting pushed into the bars. The phenomenon is caused by your back acting as a barrier between the high and low pressure zone, and the differential is literally trying to suck you into the area behind the shield.

The whole thing is easier to comprehend if you lose the mindset we all grew up with. Wind does not blow, it sucks. Airflow is induced through pressure differential, with low pressure pulling air from high pressure. Anything you can do to soften the transition from low to high will smooth things out in a big way. Over the next few weeks I'll be working on some spacers and find out what works best. Anyone who's been down the same path please chime in.

Hi Rob,

you can reduce the angle of the screen without fitting any extra parts at all.

Check out my post (number 12) on this thread. At least it will let you know if your going in the right direction.
Also trying to space the screen away from the brackets isn't easy because they are not parallel, so you end up with the bolts going in out of square.

Stu

[GRN]

Has anyone tried a Laminar Lip? I know they worked well on the ST100 but I haven't heard reports on their effectiveness on the ST13.

AgSTreak does and loves it. Runs with shield all the way down, all the time and gets good flow over his helmet.

[Redeye]

OK, after reading all these posts I think I may have the makings of a solution to this problem.
If I understand it correctly the main cause is the unequal pressure between the outside and inside of the screen which causes the turbulence. The remedies people have tried are 1. Cutting a larger section from the base of the screen to allow more airflow onto the inside surface, and 2. To change the angle of the screen.
What I think we need is to "simply" change the arc of movement of the screen when raised. Instead of the top of the screen actually moving forward as well as up it should move in parallelogram style, ie. it should remain at much the same angle as it rises. This would have the effect of increasing the distance from the bodywork in relation to the height, thus allowing more airflow and secondly moving the top of the screen closer to the rider and pushing any turbulence further behind.
All we need is one of you clever engineering types to work out the changes that need to be made to the struts that control the screen and voila!

I am a self-taught aerodynamicist who studied with both Lego and Meccano as a child so this is fool-proof .......... or I may be talking utter bollocks :confused:
I have attached a complete set of the technical drawings required to explain this wonderful theory. Patents applied for!

[CrashTestDanny]

Just had a look at the Clearview website. Not exactly overflowing with information. ST1300 not even listed!

Or am I missing something?


I wrote to the clearview guys and they sent me some info - enough that I bought their shield - it's supposed to arrive today and I'll post something about the results after my ride on Saturday. :)

But frankly, I wish I had known about raising the bracket first. The bracket is bolted into the low position by default, raising it to the high position raises the shield by 2.3 inches without changing the angle, which is what I was looking for. Raising the bracket reduced the turbulence on my head significantly.

I'll post the pics from clearview later on - can't seem to upload them right now.

[Fireball18]

Just had a look at the Clearview website. Not exactly overflowing with information. ST1300 not even listed!

Or am I missing something?
I just talked to Clearview this AM and they are mailing out my shield today. Should have it by Friday. (I hope) I ordered the GT large, which is actually, only sightly larger than the stock OEM windshield, but better designed.

I mentioned that their website didn't mention the ST1300, and John (I believe that's his name) advised me that he is currently in the process of doing a complete redo of their website, to include enabling an online ordering feature. He admitted that the "current" info is 3 years old. So hang in there guys--the new Clearview Shields' website is just around the corner.

[stuey]

OK, after reading all these posts I think I may have the makings of a solution to this problem.
If I understand it correctly the main cause is the unequal pressure between the outside and inside of the screen which causes the turbulence. The remedies people have tried are 1. Cutting a larger section from the base of the screen to allow more airflow onto the inside surface, and 2. To change the angle of the screen.
What I think we need is to "simply" change the arc of movement of the screen when raised. Instead of the top of the screen actually moving forward as well as up it should move in parallelogram style, ie. it should remain at much the same angle as it rises. This would have the effect of increasing the distance from the bodywork in relation to the height, thus allowing more airflow and secondly moving the top of the screen closer to the rider and pushing any turbulence further behind.
All we need is one of you clever engineering types to work out the changes that need to be made to the struts that control the screen and voila!

I am a self-taught aerodynamicist who studied with both Lego and Meccano as a child so this is fool-proof .......... or I may be talking utter bollocks :confused:
I have attached a complete set of the technical drawings required to explain this wonderful theory. Patents applied for!


Hi Red,
the trouble is the screen mounts follow a track which is curved, rather than using a parallelogram linkage, so I'm not sure how your going to achive your aim.

Stu

[CrashTestDanny]

I'll post the pics from clearview later on - can't seem to upload them right now.

Here are the pics I promised. My clearview just came in, so I'll have pics of the smoked screen on a pretty red bike soon!

[Redeye]

REDEYE - We Brits have a great option, which is the Flip Top windshield from the UK supplier 'Bike-Quip', based in Camberley, Surrey.

This longstanding debate regarding after market screen options is widely shared on both sides of the Pond. I suggest that you consider the discussion(s) posted on the following thread [on another forum]: Link=

http://groups.msn.com/ST1300US/general.msnw?action=get_message&mview=0&ID_Message=63262&LastModified=4675528568078761023

I have the 1" taller and 2" wider version of the Flip Top, which you can acquire from Keith Munro (Bike-Quip's proprietor) for just £75 including P&P.

I recommend this product - getting it was one of my better after-market buying decisions.

Good luck. I hope you solve your back-pressure problem, which incidentally, I have never experienced either with the original stock screen -or- my new Flip Top replacement screen.

Regards

KEITH (in Cornwall)

Took your advice Keith but looks like it's not the solution for me.
Apart from the weave in the thread it shook SWMBO around like a rag doll.

See this thread http://www.st-owners.com/forums/showthread.php?p=44694#post44694

[Rob (from Hoosierville)]

I took a suggestion from another poster and adjusted the shield to the taller setting on the brackets. Now with the electric adjustment all the way down I get clean airflow hitting me in the face and neck with no buffeting. (I'm 5'11" with a 32" inseam) At about 85 or 90 the velocity pressure of the airflow (still clean and no buffeting) gets a bit much and I raise the shield about an inch or two to take the airstream just above the top of my helmet. Still clean airflow and no buffeting. In the rain I lift it another inch or so. At the tallest adjustment electrically that I use it's only about 1/3 of the way up. As a result the angle hasn't flattened out much and buffeting (as well as backpressure) is minimal if non-existent.

Give it a try. This is a 15 minute fix and it really works.

[Marshal_Mercer]

I took a suggestion from another poster and adjusted the shield to the taller setting on the brackets.
<snip>

Give it a try. This is a 15 minute fix and it really works.

I have done this, too. It works. Not only is the airflow quieter, gas mileage went up three MPG! Many more splatted bugs noticed on the rider side of the shield.

Marshal

[vnsfxr]

Swapped the brackets today..........left the key on while I went in the house for a soda got distracted. So now I know the battery is only good for 15-20 min after you've been playing with the shield checking clearances.

Oh well haven't got to use the battery tender in awhile.

So the ops ck will be tomorrow going to work.