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Tucking in behind screen?

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NJD
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PostPosted: 19:08 - 20 Jun 2018    Post subject: Tucking in behind screen? Reply with quote

Thread that's a thread but makes you wonder why its a thread, for larks and interest.

So recently I went on a ride along the faster dual carriageways (60,70) -- that is compared to what I'm used too: 30,40 and sometimes 50 -- and tucked in behind the screen. I wasn't there for long, mind, because my exit approached (literally just a short sprint up and down a stretch of road) so didn't really get to see if it made a difference.

Again, tonight, on a 40 in some wind I caught myself doing it again but popped back up when there was someone beside me and I realised I must have looked like a donkey getting nowhere fast.

The bikes a ZR-7S which, in effect, has an upright seating position and tucking in means not race bike like but more leany forward to try and help air flow over the helmet and reduce drag. It doesn't help I've got a house brick (gopro) on the side of my head, mind, and I realise a lot would have to do with helmet, screen and rider height, perhaps, but have never really bothered with feeling like I need to tuck in before, including riding similar speed roads in the past.

So, in effect, my question, if you like, is does it really make a difference; how many of you do it or am I being a donkey attempted to reduce drag, and wind effect, by "tucking in"?

Might start leany-forward on commutes because "Nice bike, mr." <eyeroll.jpg>.
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Howling Terror
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PostPosted: 19:16 - 20 Jun 2018    Post subject: Reply with quote

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Itchy
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PostPosted: 19:19 - 20 Jun 2018    Post subject: Reply with quote

It makes a difference. A small one.

On my CBR at motorway speeds ducking behind the screen gives me more speed at a certain amount of revs than not tucking in. It's probably only around 500-1000 RPM though. Less RPM = fuel use similar to how you go up gears.

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andym
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PostPosted: 19:21 - 20 Jun 2018    Post subject: Reply with quote

I find it makes a big difference... especially popping up when almost flat out
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Nobby the Bastard
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PostPosted: 19:28 - 20 Jun 2018    Post subject: Reply with quote

When riding along at 90 on my FZ, I found that dropping down under the screen resulted in a speed of 95 with no change to throttle position.
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yen_powell
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PostPosted: 19:32 - 20 Jun 2018    Post subject: Reply with quote

I have done it in very bad side winds because along with a bit of counter steering it helps when passing a lorry in an exposed area of motorway. I have no idea if it is lowering my c of g or if it just makes me less of a sail but it definitely helps me stay straight and mucky pants free.
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kgm
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PostPosted: 21:03 - 20 Jun 2018    Post subject: Reply with quote

Makes a difference at higher speeds, particularly at the top end. My CG gets about another 5mph if I go as flat and small as possible.

Realistically unless you're looking to duck out of the airflow/weather (makes a difference to stability in windy conditions or passing trucks as you're body gets blown around less) then I don't think there's much point on a larger bike unless racing or really going flat out. I reckon the fuel savings will be minimal unless over a large distance and if you want to go faster, just wind it on more. Under 70 there's not much point. It's worthwhile on the 125 though on more open roads if you're in a hurry.
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stevo as b4
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PostPosted: 22:23 - 20 Jun 2018    Post subject: Reply with quote

Going prone gave me an indicated 85mph on a 200cc trail bike at part throttle (+10mph). It adds quite a bit to aerodynamics when the natural seating position makes you like a huge sail at full mast.
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Teflon-Mike
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PostPosted: 22:37 - 20 Jun 2018    Post subject: Reply with quote

Aerodynamics dont have a significant effect below about 6omph.. but frontal area does.

If you look at the old mag tests, they always used to quote two top speeds, one achieved prone, sat up, one achieved 'tucked'. Difference, even on something small and unfaired like a H1oo could be quite marked, like 5mph or so.

On something bigger? Well, to notice the difference in top speed, you would have to be trying to do insta~ban speeds, even on something as mundane as an ER5.

Main reason for getting tucked then isn't to go faster, but take pressure off your upper body and avoid wind buffet, and in that, it can make a much bigger difference, especially on a longer motorway haul.
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Dave70
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PostPosted: 23:30 - 20 Jun 2018    Post subject: Reply with quote

The only reason I try to tuck down behind the screen is to avoid some wind buffering on motorways. I've never noticed if the bike gains any mph though, as the last thing I'm looking at is the speedo at those speeds.
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barrkel
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PostPosted: 00:02 - 21 Jun 2018    Post subject: Reply with quote

As you head into 130-150mph territory you tend to want a bit of shelter from the wind blast, it gets tiring on the neck. I crossed a chunk of Germany like that on my VFR, lower mileage so a few more petrol stops but the speed made up for it.

Didn't make a whole lot of difference under 100mph on the VFR, but I guess it might on a bike where you sit more upright (but the VFR is somewhat upright compared to full-on sports bike).
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andym
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PostPosted: 01:21 - 21 Jun 2018    Post subject: Reply with quote

barrkel wrote:
As you head into 130-150mph territory you tend to want a bit of shelter from the wind blast, it gets tiring on the neck. I crossed a chunk of Germany like that on my VFR, lower mileage so a few more petrol stops but the speed made up for it.

Didn't make a whole lot of difference under 100mph on the VFR, but I guess it might on a bike where you sit more upright (but the VFR is somewhat upright compared to full-on sports bike).


I've never noticed tiring on the neck..... I've found when "making progress", sitting upright is good for scrubbing a bit of speed, but that's usually 140+
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Baffler186
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PostPosted: 08:38 - 21 Jun 2018    Post subject: Reply with quote

Yes big difference at higher speeds, haven't noticed any speed gains because I don't care, but it's certainly quieter on the old helmet down there on the tank
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Rogerborg
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PostPosted: 08:57 - 21 Jun 2018    Post subject: Reply with quote

Itchy wrote:
ducking behind the screen gives me more speed at a certain amount of revs

Are the tyres spinning when you're not tucked? Or is the clutch slipping? Eh?

As above, it matters above legal UK speeds. However, I'd advocate improving your environment rather than capitulating to it, and fitting a taller screen.
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weasley
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PostPosted: 09:18 - 21 Jun 2018    Post subject: Reply with quote

I used to tuck in on my last bike sometimes but found that when i did, whilst things got quieter and less buffety, I couldn't see the mirrors any more. And it made my neck ache from having to look up all the time.

It didn't affect the gearing though. And can't.
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weasley
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PostPosted: 09:19 - 21 Jun 2018    Post subject: Reply with quote

Itchy wrote:
On my CBR at motorway speeds ducking behind the screen gives me more speed at a certain amount of revs than not tucking in.


No, it really doesn't.
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recman
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PostPosted: 09:57 - 21 Jun 2018    Post subject: Reply with quote

I'll try and tuck everything in at warp speed, more for comfort than aerodynamics because naked bike.
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fatjames
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PostPosted: 11:26 - 21 Jun 2018    Post subject: Reply with quote

andym wrote:
I find it makes a big difference... especially popping up when almost flat out


Agree. [private road disclaimer] Doing around 140 behind the screen on the CBR, if I pop up, the speed drops down.
If I had to stop in a hurry, I'd want to be up in a hurry too.
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chris-red
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PostPosted: 12:47 - 21 Jun 2018    Post subject: Reply with quote

It makes a big difference at silly speeds, at the IoM I tucked in behind the screen at 100+ on the unrestricted sections, you feel a definite boost in acceleration.
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DrDonnyBrago
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PostPosted: 12:51 - 21 Jun 2018    Post subject: Reply with quote

Itchy wrote:
On my CBR at motorway speeds ducking behind the screen gives me more speed at a certain amount of revs than not tucking in. It's probably only around 500-1000 RPM though. Less RPM = fuel use similar to how you go up gears.


I didn't realise they fit CVT to CBRs nowadays?

For the same gear, at the same speed, the revs will be identical regardless of load placed on the engine unless either the clutch or tyres are slipping. The gearing is fixed, the relationship between rpm and speed is therefore fixed.
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stevo as b4
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PostPosted: 17:28 - 21 Jun 2018    Post subject: Reply with quote

It makes a fuck ton of difference on a bike that sitting bolt upright flat out is doing 95mph. Laughing

General rule is on big bikes and less generously faired ones, people are tucking in at high speed to reduce noise, buffeting and improve comfort.

On small low powered bikes people are tucking in to tease out that critical last 5-10mph.
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Itchy
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PostPosted: 17:47 - 21 Jun 2018    Post subject: Reply with quote

DrDonnyBrago wrote:


I didn't realise they fit CVT to CBRs nowadays?

For the same gear, at the same speed, the revs will be identical regardless of load placed on the engine unless either the clutch or tyres are slipping. The gearing is fixed, the relationship between rpm and speed is therefore fixed.



I worded it badly my bad...

My general point being is if you reduce your air resistance say by tucking in then you're not losing as many horses to air resistance. Take the fairing off a Busa and it will have a considerably lower top end than in its natural faired state.
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Val
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PostPosted: 18:57 - 21 Jun 2018    Post subject: Reply with quote

Blimey I read this initially as fucking in behind the screen Laughing

And I don't have a screen Crying or Very sad

Other then that seems a good idea...
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NJD
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PostPosted: 22:10 - 21 Jun 2018    Post subject: Reply with quote

Teflon-Mike wrote:
Main reason for getting tucked then isn't to go faster, but take pressure off your upper body


Is an interesting comment and one that reminds me that I went through a period of not riding without a wind collar on the touring jacket, regardless of weather, for want of keeping the pain away from my upper neck area.

NJD: Coming to a NSL near you tucked in tight with no idea what he's doing.
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redeem ouzzer
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PostPosted: 22:19 - 21 Jun 2018    Post subject: Reply with quote

OP needs to remove the GoPro from his lid. You look a tit and it causes aerodynamic issues as well as increased risk of injury when you crash. If you really need to videotape every journey then mount it to the bars or headstock.
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