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Thread: Tankslappers explained

  1. #1
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    Tankslappers explained

    Shamelessly stolen from www.sportrider.com

    1. The “tankslapper” is a very frightening experience. Usually occuring when accelerating hard over bumpy pavement, a tankslapper ensues when the front tyre becomes airborne, then regains traction outside the rear tyre’s alignment. The resulting deflection bounces the tyre off to one side, followed by another bounce in the opposite direction as it contacts the pavement again. Unless the bike’s steering geometry is able to damp out the deflections quickly, the resulting oscillations from the front tyre as it bounces back and forth will swiftly gain in strength, causing the bars to swap from side to side with increasing ferocity. The oscillations can be violent enough to rip the bars out of your hands, and fling your feet off the pegs. You can guess what happens next.

    2. The easy cure for this problem is a steering damper. Many sportbikes now come stock with one, as the radical steering geometry needed for quick handling can otherwise cause some instability in certain situations. While a steering damper is an easy fix, it shouldn’t be a cure-all; if you’re forced to adjust the steering damper’s stiffness (if available) until you can barely turn the bars in order to keep the bike’s handling stable, there is a problem somewhere in your chassis setup. A too-stiff steering damper can also cause handling problems by itself; if your steering damper is adjustable, and you find that your bike won’t hold a line (especially in slower corners), or gets into a small wobble or oscillation in high speed corners, try backing off the stiffness a little and see if it helps.

    3. Not all sportbikes need a steering damper, however. Many have steering geometry setups that offer quick handling, while still providing the necessary stability to damp out any front-end oscillations. In most cases, one of the biggest contributors to a tankslapper is your body positioning and grip on the bars. Some people ride in a more upright position when carving corners, but when accelerating over bumpy pavement, that upright body position puts even more weight transfer to the rear, which causes the front end to get lighter. Also, the more upright torso means that your grip on the bars is tighter in order to stabilize your upper body. That firmer grip feeds more input into the front end, something it doesn’t need while it’s busy trying to damp out the inputs from the bouncing front tyre. It actually forms a vicious circle: you grip the bars tighter because they’re starting to flap back and forth, but that only feeds more input into the front end, compounding the problem further.

    4. The easiest way to avoid tankslappers while accelerating over bumpy pavement is to—believe it or not—keep a relaxed grip on the bars. Relaxing your grip on the bars means you must lean forward in order to assist in keeping your torso stabilized. This helps put more weight on the front end, which keeps the front tyre on the pavement. Since you’re not using your arms to stabilize your upper body, get your weight onto the footpegs so that you can get your body as far forward as possible; this also allows you to grip the tank with your knees for more stability.

    If you do get into a tankslapper, keep your weight forward and—as hard as this sounds—maintain a relaxed grip on the bars. Let the motorcycle’s chassis deal with damping out the oscillations. Don’t try to be a human steering damper; you’ll only make the problem worse. Tankslappers can definitely soil your undies; but if you’re able to deal with them correctly, you’ll usually ride through them before you know it.
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  2. #2
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    Nice post. All of it true too. Had a beaut this year whilst passing a car and it slapped so badly that I couldn't actually hold the bars properly but as you correctly say, it just sorted itself out. I had to sort out the brown undies myself

  3. #3
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    Probably the most frightening thing a bike can do. You're usually just a passenger waiting for the splat.
    I had an old CB750 start slapping at around 140 km/h, I managed to get it down to around 100 - 110 before it spat me off and destroyed itself.
    I clearly heard the front tyre chirp as it went from lock to lock.
    Speed doesn't kill people.
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  4. #4
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    Good thread.

    Well done. Tankslappers are like your first nookie, they sneak up on you when you are least prepared for it.
    Same sort of effect too when you think about it.
    So far so good on both counts, sadly only got the tankslappers to worry about these days!
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  5. #5
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    He he, never had a full on lock to lock slapper, a few shimmies and shakes but heres how NOT to handle one.... Crossed up wheelie landings can trigger em too.



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  6. #6
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    Quote Originally Posted by oldrider
    Well done. Tankslappers are like your first nookie, they sneak up on you when you are least prepared for it.
    Same sort of effect too when you think about it.
    So far so good on both counts, sadly only got the tankslappers to worry about these days!
    Um... What exactly did you have your first nookie with?
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    You say "no one wants to fuck with some large bloke on a really angry sounding bike" but the truth of the matter is that you are a balding middle-aged ice-cream seller from Edgecume who wears a hello kitty t-shirt (in your profile pic) and your angry sounding bike is a fucken hyoshit - not some big assed harley with a human skull on the front.

  7. #7
    I had my first tankslappers at speed on the beach.They are horribly ferocious,more so than on the road - sand builds up in front of the contact patch and slams the forks onto the stops with a clang...once I had to stand on the pegs and let the bike gyrate beneath me,you just couldn't stay in that place.The only plus is that it's a softer landing in the sand...but I was never spat off.

    I decided I had better retire my old XS1 when I had a major tank slapper at 150kph coming up the hill from Riverhead Forest to the gun club.So I go back a month later on my superb handling XLV750 - and had another tank slapper at the same speed on the same corner...so it wasn't the bike after all!

  8. #8
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    So with "Roxanne" being such a front heavy bike, would this be why I bare have had even a hint of tank slap from her or are Honda steering geo. just fu*ken good? By the way even by cracking the throttle full open on her, she barely lightens the front end.
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  9. #9
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    I had a tank slapper on a pitbike ! heaps of fun.

  10. #10
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    No, No... don't do this to me...

    I always thought a tank slapper was a loose/good time woman who likes sex on the tank of a bike...

    That is what I still want to think... and it happens lots...

    Soulds like much more fun than what is posted above!!!!

  11. #11
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    One of the relatiely few things on bikes that scare the shit out me. Classic "deal with" is to keep power lightly on, shift weight forward until it damps itself out. Easier said than done!

    (Always a good idea to have weight forward on exit from a corner BTW - helps with the dreaded slapper, and helps keep the front end down. Of course, you may pay for that with the rear wheel breaking away if you are too heavy handed on the throttle. Sigh. No such thing as a free luinch, but I'd rather have the rear misbehave than the front)

    I've only had a couple of true tankslappers (as opposed to heavy steering wobble and weaving), could very happily live with never having another.

    I reckon that it's about the nastiest thing out on a bike. And always happens at speed.

    Impossible to induce for training purposes , either.
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  12. #12
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    Patrick.. does your wife know of your.. interpretation of a Tank Slapper are?
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  13. #13
    Nearly all sidecars go into a shimmy at 35mph (sorry,sidecars are very Bwitish y'know).One of my chairs was good hands off - but I'd give the bars a smack and sit back and watch it shake smacking the steering stops,then I'd just touch the bar and it'd stop.But trying to teach my wife to ride my big outfit it'd go into it's shake,and she'd freak out thinking she was in a tankslapper - understandable I suppose as she had consusion once from being spat off in a tankslapper.

  14. #14
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    Quote Originally Posted by Motu
    understandable I suppose as she had consusion once from being spat off in a tankslapper.
    Things we did not need ta know about Motu's husbandly practices Hope ya at less had the garage door closed at the time (just teasing ya Motu).
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  15. #15
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    Whoa! your wife is a legend Motu!!
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