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Slipstreaming...

Discussion in 'General Motorcycling Discussion' at netrider.net.au started by FoxRiderJ, Sep 24, 2011.

  1. First off, i do not promote this type of riding, ever.

    I've read about slipstreaming countless of times, and seen it done usually in the pro racing circuit. But on Friday night it was the furthest thing on my mind as i was on the freeway headed for home.



    Just cruising along at 90 on the left lane, i could see a Toorak tractor in my mirrors (a sonata i think it was), and ahead i was quickly approaching another vehicle, which was going at a much slower pace than the indicated speed if i was rapidly approaching him doing the posted limit.

    I turn on my signal to change lanes, but i catch the flicker of the sonata behind me - he decided he didn't want to be behind me any longer, and darts past me on the right. I change lanes as soon as he passes.

    HOLY COW. All of a sudden it felt like what i could only describe as being in a turbulent wind tunnel. Wind roaring louder than ever before. I could feel the bike and i being sucked forward, but with wind resistance pushing on both sides; a little air pocket. Then i notice my speedo, which had just surged past 100kph. I wondered how, as i was keeping a steady throttle on 90. I look ahead and the sonata is just surging froward. My speedo now crosses 120kph, again with minimal effort. I've never been able to push my little 250 past 120 before. I freak out when the needle crosses over to 130, thinking shit this canot be good.

    I force the bike back into the left lane, and immediately the howling wind recedes to the familiar level i've grown accustomed to with my Shark helmet. It was then i realised i was slipstreaming.

    I can't deny it felt absolutely incredible, and i'm amazed at how quickly the speed picks up, but it is a VERY STUPID and DANGEROUS thing to do.

    Just thought i'd share a story with my fellow netriders for you know, science. :angel:
     
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  2. I often do it behind trucks on long overnight drives but I make sure they know I'm doing it. Makes for a good way to save fuel and keep alert IMO
     
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  3. Yep behind a big semi the effect is huge. i have done it on the hume before and i noticed a drop in about 1-2 thousand RPM not to mention massively reduced wind noise and a general feeling of being sucked along by the truck.

    Can be a bit dangerous however im fairly certain my bike can pull up a lot faster then a B double, i would say a bigger concern is a re tread blowing out, or the fact that you cant see the road ahead causing you to collide with a large pot hole or some roadkill etc.
     
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  4. When my Dad was a young man, riding a CT90 for the garage he worked for, out on a highway, two truckies decided to give him a lesson in slipstreaming. One overtook him, the other stayed behind, then they closed the gap and took him up to speeds that the little Honda had never seen. He recalls it as rather harrowing.
     
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  5. one of the best 'free' tools avaliable for long distances!:deal:
     
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  6. I learned this trick riding my RD-250 Yamaha on the New England Highway at 5:00 in the morning back in the early 70s. It IS fun sitting in 'the pocket' and you REALLY notice it when you drop out of it :LOL:....
     
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  7. On my daily commute from east to west in Victoria, I choose the semi-trailer that is going at reasonable speeds and stay behind it. Fuel consumption drops, less effort and less wind bashing in all directions, especially on the days when the wind is coming towards you at 60+ km/hr on top of freeway speeds. I try and stay towards the left wheel track of the truck but not far enough to get the left wind bashing of the turbulence, this way the truck can pick up anything sharp on the road and I can change lanes quicker.

    I don't think it's too dangerous, just don't do it during peak traffic.
     
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  8. #8 smileedude, Sep 25, 2011
    Last edited by a moderator: Oct 24, 2015
    With a semi you can get it quite far back from the truck (not a safe distance, but a normal gap as far as aussies are concerned). The main danger I find when I do it is passing another truck, especially on a windy day. You get wierd unpredictable gusts and get blown about any which way.
     
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  9. wat
    :-s
     
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  10. It works through flood ways as well. you need to be close as you can get to the back of the truck tho and hope like hell he doesnt stop or youre up to your guts in water.
    Back in the late 80's after half of outback Qld was underwater we came to afloodway with about metre of water on it. watched a four wheel drive come through from the other direction so we knew the bridge/roadway was still there.
    too deep for the GSX1100 deepest it was hitting the top of the tyres on the 4WD.
    Semi came past us and we watched the water flowing away from his wheel tracks. Hmmm.
    next one came up and I slotted in about 2? metres off the back of the truck. Held our feet up out of the water and got through fine.. Water to our sides looked like it was about seat height. long time ago so it probably gets deeper the older I get..
     
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  11. Thats how Moses crossed the sea. Him and the slaves just waited for the next semi.
     
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  12. So thats what all those buggers were doing??
    Although the water was kinda brown rather than red..
     
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  13. Like so many things on bikes, sitting in the pocket has its uses and advantages, but also its dangers. There are some serious traps for new (and old) players. Like roo carcasses popping up between the rear wheels right where you're about to ride.

    Don't draft car carriers. Just don't.

    The skinny dog used to be a good one, because those blokes used to get along a bit. They seem to have toned it down a bit these days, but I've sat bemused in the draft of a dog several times with the gauges showing over $1.30, and the bloke in the 'hound usually knows where he's going and what he's doing.

    Truck drivers generally hate having a bike up their date, because you never know what the evel kenevil is going to do, half the time you can't see him, and if he comes to grief under your wheels or nearby, who's going to get the blame? That's right - pill popping homicidal truck drivers again. Somebody should step in and take greater control and oversight of the road transport industry and chase those damn cowboys out. Right. Just what a working man needs.
     
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  14. Going behind a truck reduces the affect of wind drag. thus meaning the engine does not need to rev as hard to maintain 110 kph. Not sure what you dont understand? my bike has an 18,000 RPM rev range, a drop of 1-2000 on my bike is nothing compared to what it would be like on a big bike.
     
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  15. I let this ride the 1st time, but you're repeating it.

    If your revs have dropped, there are two possible explanations. You're going slower behind the truck, because he is, or your clutch was slipping.

    There is a fixed relationship between engine speed and road speed. If there's not, then you have a continuously variable transmission (unlikely - some scooters do but motorbikes mostly don't) or your clutch is slipping, or (sorry - trying to be polite about this) you don't know what you're talking about.
     
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  16. unless the clutch is slipping, there should be no difference in engine revs at 110kph in a given gear behind a truck, on a dyno, or into a hurricane.
     
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  17. see above posts. I don't know what your bike's power curve is like, but one other possibility: you were able to shift up a gear, thus reducing engine speed, because your bike did not need to produce as much power to push you and itself through the air due to less air resistance.
     
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  18. #18 smileedude, Sep 25, 2011
    Last edited by a moderator: Oct 24, 2015
    You can however notice the difference in how much throttle you give it. I can go at 110 with less than half a twist if behind a truck while im close to full if not. Im not sure if this equates to half the fuel used. Is it a 1:1 ratio of twist to petrol use?
     
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  19. Mythbusters did an extensive test on it with great results.

    I do it compulsively.
     
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  20. i just fell off my chair laughing.

    now i have a headache from the fall... :(
     
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