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Purpose of screens on sportbikes

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SirFallalot
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PostPosted: 00:17 - 11 Sep 2021    Post subject: Purpose of screens on sportbikes Reply with quote

Bit of an awkward question...they're obviously a big part of aero, and when sitting "upright" they do deflect all the air from the body to just below the helmet, making mway speeds feel like 50mph on a naked, however, for sustained rides or higher speeds, how are you meant to tuck in? Look just over the screen, or chinbar-to-tank took through the screen?

On the former, there is far too much turbulence, even with earplugs the noise and force is unbearable, on the latter, I guess the field of view is fine if you're so that fast you only need to look straight, but that's not always the case, with commonly seen tinted screens you can't see fuckall, and the eyes will be almost rolling up in your head too I can't see this being any better than sitting normally?

So really, if you're cruising for extended periods, how are you meant to sit? Is this where double bubble screens come in too? Although if they redirect the air any further up then you'll get the turbulence sitting upright, so even worse off? I suppose different bikes will be different, my example is the zx9r.
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trevor saxe-coburg-gotha
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PostPosted: 07:07 - 11 Sep 2021    Post subject: Reply with quote

I have a '99 and maybe it has an after market screen on it because I honestly don't feel any undue wind blast - even at 140 for a few minutes it seemed reasonably okay, I thought. I do wear earplugs though. One thing's for certain - it's a LOT less buffety than my '00 cbr600f was. In fact I'd go so far as to say it's a quiet, refined and comfy bike at all speeds. Suss out if you've got an OEM screen and what the after market ones are like if you haven't already is all I can think to say, unfortunately. The forums @ ZX9r.net are really useful and screens will almost certainly have been discussed in passed threads in the E model forums. It's just a matter of finding them.
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doggone
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PostPosted: 08:03 - 11 Sep 2021    Post subject: Reply with quote

At higher speeds the wind hitting upper body takes some weight off your wrists, on a sports bike at lower speeds you can often start to get tired wrists and forearms doing long trips.
They aren't expecting road riders to tuck in like they might on a racetrack - for more than a few seconds anyway.
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stinkwheel
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PostPosted: 08:39 - 11 Sep 2021    Post subject: Reply with quote

Try doing the same speed on a naked bike and you'll appreciate just how much force the fairing is actually taking.

You sit normally and it generally creates a "bubble" of air that flows up over your helmet. If you are getting turbulance, your head is probably up out of that bubble, try ducking it down a couple of inches and it'll probably turn into a smooth flow of air, still forceful (you have your head in a 90mph wind) but smooth. If that's the case, you're a bit tall for the bike. They were designed by Japanese people who tend to be shorter than your average Brit. If this is the case, fitting a flip-up or double bubble screen will sort the problem.

If you take your left hand and move it away from the bike while travelling at speed, you can generally feel exactly where the edge of that bubble of air stops and whips your hand away in the slipstream.
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SirFallalot
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PostPosted: 00:54 - 13 Sep 2021    Post subject: Reply with quote

stinkwheel wrote:
Try doing the same speed on a naked bike and you'll appreciate just how much force the fairing is actually taking.


I do know the feeling, and the screen does work very well when sitting upwards very well, without any buffeting or extra noise yada yada, my question is, are you meant to be able to tuck in for sustained higher speeds without buffeting, and are you meant to look through the screen or just over it? Or just still sit up and enjoy the floating effect?
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Zen Dog
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PostPosted: 12:24 - 13 Sep 2021    Post subject: Reply with quote

SirFallalot wrote:
my question is, are you meant to be able to tuck in for sustained higher speeds without buffeting, and are you meant to look through the screen or just over it? Or just still sit up and enjoy the floating effect?


By "meant" do you mean "did the manufacturer intend the rider to tuck down/behind the screen at high speed"? If so, it may depend on the bike and the screen in question. On a full-on sportsbike with a standard screen, yes probably, and you're probably intended to look through the screen when tucked in. Double bubble screens etc. remove the need to tuck. On a tourer, you're almost certainly not intended to tuck, and you'd be looking through the screen a lot of the time in normal use anyway.
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stinkwheel
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PostPosted: 13:06 - 13 Sep 2021    Post subject: Reply with quote

If you're properly travelling at speed, there isn't really an option, you get tucked in or you'll land up getting peeled off the bike and flapping along behind it like a washing line. I usually still peer over the top and round the edges of the screen though. Arching your shoulders helps aerodynamics slightly as well (which is why they put humps in race leathers).

One thing I've noticed when travelling at stupidly high speeds is that the airflow over the top of your helmet can create a slight vacuum inside your lid, presumably due to the venturi effect. Although it might even be airflow over your back creating a low pressure area over your curved back like an aircraft wing. It can become quite hard work to breathe, you have to force breaths in and out.
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MarJay
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PostPosted: 13:17 - 13 Sep 2021    Post subject: Reply with quote

On track you look through the screen on straights. Trust me, I was doing it all day Saturday until I had a little mishap.
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ThunderGuts
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PostPosted: 13:18 - 13 Sep 2021    Post subject: Reply with quote

There is presumably another factor to all of this; a sportsbike isn't necessarily designed for long distance high speed cruising; "sporty" riding, on road or a track, will involve varying speeds, rather than a constant high speed pressure. Touring bikes and those designed with distance-covering in mind will tend to have fairings and screens to improve the "bubble" while allowing the rider to sit comfortably within it.
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xX-Alex-Xx
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PostPosted: 13:58 - 13 Sep 2021    Post subject: Reply with quote

Stock screens IMHO are almost always too low for street use. Higher aftermarket ones (double bubble) are usually better as they tend to be taller.
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Nobby the Bastard
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PostPosted: 14:03 - 13 Sep 2021    Post subject: Reply with quote

Meh, I'm 5'4 1/2 so stock screens are fine for me.
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Fat Angry Scotsman
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PostPosted: 14:32 - 13 Sep 2021    Post subject: Reply with quote

stinkwheel wrote:
If you're properly travelling at speed, there isn't really an option, you get tucked in or you'll land up getting peeled off the bike and flapping along behind it like a washing line. I usually still peer over the top and round the edges of the screen though. Arching your shoulders helps aerodynamics slightly as well (which is why they put humps in race leathers).

One thing I've noticed when travelling at stupidly high speeds is that the airflow over the top of your helmet can create a slight vacuum inside your lid, presumably due to the venturi effect. Although it might even be airflow over your back creating a low pressure area over your curved back like an aircraft wing. It can become quite hard work to breathe, you have to force breaths in and out.


Not to do with screens but I rode my little 125cc from Glasgow to Edinburgh on the M8 in both directions and I was struggling to keep above 60mph as the wind was blowing against me, I thought I would get in behind an HGV and use his slipstream and just plod along.

Got about 1.5 - 2.0 car lengths behind the lorry and you noticed the difference immediately, such little wind on my body and the whistling in my helmet stopped. The downside is that with the reduced airflow the engine temperature of my bike started to rise sharply. I dropped back a little further and it started dropping down again.
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Nobby the Bastard
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PostPosted: 14:35 - 13 Sep 2021    Post subject: Reply with quote

And thats why you keep your distance when overtaking a lorry doing 50-60mph. All that air has to go somewhere....
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stinkwheel
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PostPosted: 14:48 - 13 Sep 2021    Post subject: Reply with quote

Fat Angry Scotsman wrote:

Not to do with screens but I rode my little 125cc from Glasgow to Edinburgh on the M8 in both directions and I was struggling to keep above 60mph as the wind was blowing against me, I thought I would get in behind an HGV and use his slipstream and just plod along.

Got about 1.5 - 2.0 car lengths behind the lorry and you noticed the difference immediately, such little wind on my body and the whistling in my helmet stopped. The downside is that with the reduced airflow the engine temperature of my bike started to rise sharply. I dropped back a little further and it started dropping down again.


Bulk liquid tankers have the best slipstreams. If you can get behind one doing slightly above your comfortable cruising speed, you can sit there at half throttle.

The other feature worth knowing about with HGVs is there tends to be a little bit of a draw-in just as you come level with the back of the cab. If I'm passing one on a slow, light bike, I usually start at the right hand side of the lane as I pass, moving in towards the centre of the lane as I'm passing then start to move back towards the right again as I come level with the cab.
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Polarbear
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PostPosted: 16:18 - 13 Sep 2021    Post subject: Reply with quote

I fitted a double bubble to my Busa and hated it because it moved the wind blast straight to my head rather than my chest which the standard screen did.

Also, and maybe I was imagining it, but the faster I went, the better the wind protection was, even without crouching down on the tank. Better by giving me greater overall protection. Some fancy aerodynamics? who knows.
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chickenstrip
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PostPosted: 16:34 - 13 Sep 2021    Post subject: Reply with quote

I always used to get a bit of head buffeting and wind noise for years. At 6'2", I suppose I'm not really the right height for standard screens and bike design, but different aftermarket screens didn't seem to improve things much. Cured all of that by chance with a helmet purchase - HJC RPHA10. Not had any of that since.

I like Thunderguts' answer, seems to make the most sense. Sports bike screens aren't designed to be keeping the wind off for long periods, just short blasts along race track straights. There are double-bubble replacements available for some models which would probably make things a little more bearable for road use, as Polarbear mentions, but then you might get the problem he points out. If you want what sports bikes give you, on the road in everyday use I suppose you should expect to have to put up with some compromises.
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weasley
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PostPosted: 18:11 - 13 Sep 2021    Post subject: Reply with quote

chickenstrip wrote:
I like Thunderguts' answer, seems to make the most sense. Sports bike screens aren't designed to be keeping the wind off for long periods, just short blasts along race track straights.


And yet race teams put double bubble screens on their bikes for use on tracks, so who exactly is the lower screen meant for?
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Kawasaki Jimbo
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PostPosted: 18:12 - 13 Sep 2021    Post subject: Reply with quote

SirFallalot wrote:
my question is, are you meant to be able to tuck in for sustained higher speeds without buffeting, and are you meant to look through the screen or just over it? Or just still sit up and enjoy the floating effect?

All of the above, whatever works at that moment.
The option to move helps ease fatigue.
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Kawasaki Jimbo
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PostPosted: 18:13 - 13 Sep 2021    Post subject: Reply with quote

weasley wrote:
chickenstrip wrote:
I like Thunderguts' answer, seems to make the most sense. Sports bike screens aren't designed to be keeping the wind off for long periods, just short blasts along race track straights.


And yet race teams put double bubble screens on their bikes for use on tracks, so who exactly is the lower screen meant for?

The aesthete.
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chickenstrip
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PostPosted: 18:13 - 13 Sep 2021    Post subject: Reply with quote

weasley wrote:
chickenstrip wrote:
I like Thunderguts' answer, seems to make the most sense. Sports bike screens aren't designed to be keeping the wind off for long periods, just short blasts along race track straights.


And yet race teams put double bubble screens on their bikes for use on tracks, so who exactly is the lower screen meant for?


Little people. I think Marquez is about two feet high isn't he? Laughing
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MCN
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PostPosted: 18:32 - 13 Sep 2021    Post subject: Reply with quote

For the cruise you get tucked in.
For as long as comfortable.
Rest you chest on the tank. (Avoid potholes. Embarassed )
Most strain is on back of the neck.

As mentioned, If you're on a track you're not tucked for more than anything like a minute so neck strain isn't an issue there.

Screens are now wind tunnel tested for effectiveness.
Manufacturers are desperate to sell their wares.
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stinkwheel
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PostPosted: 20:25 - 13 Sep 2021    Post subject: Reply with quote

weasley wrote:


And yet race teams put double bubble screens on their bikes for use on tracks, so who exactly is the lower screen meant for?


Maybe it depends on how long the straights are on that particular track. If it's a long track with big, fast straights, getting the horribly non-areodynamic rider out of the airflow will be an advantage. If it's shorter and twistier, less is less and weight at that level of riding is down to marginal gains.
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weasley
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PostPosted: 20:39 - 13 Sep 2021    Post subject: Reply with quote

stinkwheel wrote:
weasley wrote:


And yet race teams put double bubble screens on their bikes for use on tracks, so who exactly is the lower screen meant for?


Maybe it depends on how long the straights are on that particular track. If it's a long track with big, fast straights, getting the horribly non-areodynamic rider out of the airflow will be an advantage. If it's shorter and twistier, less is less and weight at that level of riding is down to marginal gains.

I guess my point was that for production-based race bikes, they bin the ‘production’ screen and put a taller one on. So if the lower screen isn’t for racing and isn’t good for road use then what’s it for? Why not fit a double-bubble as standard? I think Kawasaki’s Jimbo got it.
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G
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PostPosted: 21:34 - 14 Sep 2021    Post subject: Reply with quote

Stock screens on street bikes - they fit in well with the lines of the bike and look pretty, so people that spunk £15k+ on a bike are pleased with their purchase when they polish it on a Sunday.
Double bubble/race screens - let you get properly out of the air flow when tucked down, with out the need to completely lie on the tank.

The ZX9R with a fairly generous fairing did well with a double bubble on race fairings. Tucked down a bit and ear plugs in, 140mph felt a lot slower and calmer than 85mph on the KLR650 I had at the time too.

I didn't try and use that excuse with the police.
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Fizzer Thou
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PostPosted: 11:10 - 17 Sep 2021    Post subject: Reply with quote

The previous owner of my 5JJ-R1 fitted a double bubble screen to it when it was only a few weeks on the road.I have found that,after riding a friend's 5PW-R1 with the OEM screen fitted that it was far too low,but it suited him okay as he is a shortarse.
The setup on my R1 suits the lines and the purpose of the bike.It was very comfortable for my 5'10" stature while sport/touring in frogland back in 2014

https://i.postimg.cc/3xSdDpbr/12605313-996350100424562-7001382163323401360-o.jpg

The barn door fairing on my FZR1000R,by comparison,is comfortable with the standard type screen.I do sometimes dip my head and shoulders a bit lower so as to get out of the windblast at 80+

https://i.postimg.cc/vBN6pf6N/20200807-175437.jpg
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