Pillion buffeting

[Old Steve]

Mrs Old Steve has really taken to riding pillion, it's "our" bike now and the other day she commented how nice the exhaust of a Bonneville sounded.  She has two jackets, two pairs of gloves, full face helmet fitted with Sena SMH10 headpiece, Draggin jeans and riding boots.     My little biker chick!

She does notice her head gets buffeted on the back of the ST1100.  Years ago she got whiplash in a car accident and especially notices the buffeting when there's a bit of side wind, though also notices it with no side wind at around 100 km/hr.

My St1100 is fitted with a ScreensforBikes higher screen (80 mm higher than the standard screen).  I didn't get a screen with vents in it either.  Would this higher screen be causing more buffeting for the pillion rider?  She's just my height, about 1.70 m/5' 7 or 8", but the pillion seat has her sitting about 75 mm/3" higher than I am.

[alans1100]

Heather notices it more on side winds regardless of the speed were travelling but usually at a 100 or below hardly anything.

I have a 10cm higher screen with the cat eyes as the OEM screen had them and they must have been there for a specific reason. I thought to relieve back pressure on the screen but I found the following from http://www.st-owners.com/forums/archive/index.php/t-129887.html

Quote

95 - 02 model years came with OEM shields with the cateyes, earlier years didn't have them.+1... the first gen ST1100 (<'95) came with a narrow, straight windscreen, featuring no cat-eyes; this design lead to quite some buffeting, especially on the pillion's helmet... besides those cut-outs the post '96 screen is also wider in the upper half, featuring a way smoother air flow to both lids, but to the passenger's helmet in particular...

End Quote

However since adding the dash shelf that has reduced the air flow from going behind the screen to going under the dash shelf so I may have enlarge the gap between the screen and dash shelf sometime.

[WendyL]

My daughter complains about buffeting, says it's better if I sit up straighter or duck down behind the screen, apparently it's at it's worst in my normal riding position.

[Yorkie]

When riding a vacuum is created behind the screen, the buffeting is caused by the air trying to fill that void, that pressure creates approx. double the speed you are travelling at. This is how a yacht gets sucked along, it doesn't get blown along.
The only way to stop this is to get a lower screen.

[alans1100]

When riding a vacuum is created behind the screen, the buffeting is caused by the air trying to fill that void, that pressure creates approx. double the speed you are travelling at. This is how a yacht gets sucked along, it doesn't get blown along.
The only way to stop this is to get a lower screen.

The reason I got a 10 cm taller screen was that the OEM screen aimed the wind over the screen and right onto my helmet cause me to get neck strain. I don't get that anymore as most of the air flow goes over the top of my helmet and it makes the ride more comfortable

[Old Steve]

The only way to stop this is to get a lower screen.

What about drilling some holes (say six 12 mm per side) low on the side of the screen where the vents would be?  Would that reduce the pressure behind the screen?

[Biggles]

The only way to stop this is to get a lower screen.

What about drilling some holes (say six 12 mm per side) low on the side of the screen where the vents would be?  Would that reduce the pressure behind the screen?

Which would be why the ST1100 OEM screen had "cat's eye" vents.
The ST13 has a gap at the bottom, but there is still some "back pressure".

[Yorkie]

The only way to stop the buffeting is to totally remove the void, that is by removing the screen, the more air allowed in will reduce it but not stop it.
There is a noticeable difference between riding alone and with a pillion, the pillion will notice a lot more buffeting and the higher the speed the worse it will get.
Read this article.
http://will.mylanders.com/outdoors/motorcycle/notes/read.pl?file=27

[alans1100]

Which would be why the ST1100 OEM screen had "cat's eye" vents.
The ST13 has a gap at the bottom, but there is still some "back pressure".

The 1100 had both

The cat eyes came in from 1995, earlier ones didn't have them......