frEEk
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posted March 17, 2005 01:25 AM
reverse tank slapper?
what do u call it when u get into a full tank slapper but it's ur rear tire dancing back and forth instead of the front one?
and does anyone have a clean pair of shorts?
back on a serious note, what's the correct technique to ride it out?
   
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Bagster
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posted March 17, 2005 05:18 AM
A Butt Slapper?
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k bryant
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posted March 17, 2005 09:30 AM
The standard term is "swapping ends". Basically where the rear wants to change places with the front. It's definetly not fun when taken to the edge, because more often than not, it is the number one cause of a "high-side". Believe me, that is one of a racers worst nightmares... There are still times to this day, where I will wake up in a cold sweat from recalling high-sides or near high-sides..
The "correct technique to ride it out"? Pure instinct, reaction, and a little luck.... Having had it happen an uncountable amount of times, I'm going through the action/reaction in my head now (in the moment....).
It comes from lost traction. Too far on the edge of the tire (combined with too much throttle)and it slides out. It doesn't matter if it's a racebike, street bike, Harley or Moped; your reaction is what saves it as it starts swapping. The suspension continues to try and counter-act/smooth out the action, as interia somewhat takes over (kinda like a gyro). It stops by a combination of modulating the throttle, transferring weight, changing angle of lean, and traction coming back.
Chopping the throttle is the worst thing to do, as it more often than not, results in a high-side... The obvious problem is that it is most people's reaction to indeed chop the throttle; sometimes they get lucky depending on a host of circumstances (speed, suspension, traction, bike mass, etc..)
But it is a really good question. Hard to put a finger completely on how to consistently counter-act. There's just a certain feel you get from experiencing it consistently and knowing how to react/deal with it. From my standpoint, it's reacting quickly and smoothly depending on how violent the swap is. Otherwise interia & gyro affect take over and your saving it can depend on those two reacting with each other as well.
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frEEk
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posted March 17, 2005 11:13 AM
thanks for the great answer kerry! sounds like there isnt much of a standard technique like for tank slappers tho. i'd have to say blind luck is the element that saved my butt. i definitely felt like i was gonna be pitched and i did let off the throttle partially (not completely tho), but i think the fact that my tire has so little traction (cold and crap on the pavement) was what saved me. when it hooked up again and swapped back, it couldnt grip enough to fully highside. repeated the process once more (abck and forth) then settled. one thing i noticed was that my natural reaction was to take the weight off my rear and stand up just a touch. wonder if this helps or makes it worse?
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zx23rr
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posted March 17, 2005 11:40 AM
It "depends" - kidding aside, once you lifted you ass out ot the seat you lowered the C of G but also allowed you to maintain better control -ha! - of the situtation as the bike was not moving you around as much therefore not letting any extra inputs into the bars. That said, if you are power sliding the rear, the last thing you wish to do is move around. Cold tires, cold pavement, and lots of throttle is always a fun combination.
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canadamaxxer
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posted March 17, 2005 12:54 PM
I've always been told to apply the rear brake and leave it locked up until you're stopped. At least if the tire is locked, you're less likely for it to grab and high side you..... In fact that is the information put out by local riding courses and the provincial government.....
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k bryant
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posted March 17, 2005 02:53 PM
Not sure if you're kidding or not, but thatz about the worse advice I've heard in awhile. Locking the rear brake would cause you to lose what little control you have left and makes no sense at all. It has little bearing on the affect of grabbing and high siding you. You can high side easily with the back brake locked. All that has to do with is lean angle. Once your locked up and reach close to vertical, inertia takes over and you're getting ejected into orbit. Your only hope of saving it in a situation as described is staying on the gas in some aspect. Lock up your brakes = loss of control. That applies for Cars & Bikes.
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canadamaxxer
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posted March 17, 2005 03:26 PM
 Edited By: canadamaxxer on 17 Mar 2005 15:26
Seriously, that is what the government and local rider training courses are teaching!!! Their logic is that the locked rear wheel will effectively "pull" the rear of the bike back into line due to the increased friction. They also mention that the moment the wheel is unlocked, it will grab and begin the high side process.
I'm just the messenger here......
I have never had this situation happen myself....other than on a MX bike, and I cannot remember how I got out of it...or if I did at all 
If I can find the book (my fiance took the tests last year), I will scan it and post it....
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frEEk
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posted March 17, 2005 04:09 PM
no idea if that theory pans out in practice, but it sounds logical. problem is getting ur rear tire to lock that quickly. hell, my back brake doesnt do much at the best of times. i'd be concerned that in the transition from over-spinning and locked, you would hit that wheel speed where it woudl hook up (albeit briefly)
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canadamaxxer
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posted March 17, 2005 05:05 PM
Edited By: canadamaxxer on 17 Mar 2005 17:08
To support this theory........I think of the analogy of the drag chute behind an airplane......the drag pulling on the rear of the vehicle will attempt to straighten and then maintain the straightness of that vehicle.
I would also think that if your bike was already sliding (as a result of the rear end swapping back and forth), you would have no problem locking the wheel.
I do know (from my experience anyways) that if the back wheel begins to slide out on a corner I would not slam on the rear brake....I would try to flat track it out of that situation using countersteering, a bit of throttle, and prayer. Is this "tail wagging" situation the same as that cornering issue??? It seems somehow different.....probably because in the tail wagging situation, the bike is upright, not leaned into the corner... ****IF I am reading frEEk's original post...riding down the road and the rear end begins to wag.....not in a corner, but just cruising....possible over some washboard*****
*******I will say once again that I have no experience with this......I am just relaying what I've been told, and have been trying to figure out what the logic of that suggestion is.....*************
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k bryant
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posted March 17, 2005 05:35 PM
The only thing the theory supports is slowing down something that essentially has the wheels in-line and/or where they are supposed to be pointed. Stability is a whole other issue, as an airplane or Top Fuel Car (for additional instance), has more than 2 wheels, has wings and/or foils to help stablize it and doesn't rely nearly on any balancing affect of two wheels. The violence of the chute opening is also substantial. Can you imagine how it might jerk you into a straight line? You'd probably be worse off and I doubt you'd even be able to hang on from the G-out or balance it. Though I'd like to see it tried..
These are simply two different matters and I don't see the correlation. One's based on wind drag, and not limited by traction (necessarily). The original question is based on available friction, interia and gyro affect.
The "tail wagging" situation is more likely than not, to start in a corner. But in most instances, it continues when you straighten it up. That's when the fun really starts. So no, it's not really different. Even if you haven't experienced it yourself, you've more than likely seen it in racing (on TV or otherwise).
The theory is basically the same on your MX bike. I ride moto (YZ450F) all the time. The tank slapper and/or swapping applies the same; pavement or dirt. The only difference is slower speeds and the dirt is softer when you bale...... Luckily, most of my tank slappers, swappers, and high-sides happen in the dirt (for the most part...)
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frEEk
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posted March 17, 2005 06:39 PM
CM, it happened on a very slight turn, just as i was completing turning left onto the road. luckily i was only doin about 50km/h at the time. lean angle was pretty much non-existant at that point. good thing i didnt get pitched as i had a backpack full of groceries on, including a dozen eggs. that woulda been messy
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diablodcielo
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posted March 19, 2005 11:32 AM
I've only had rear tank slappers on stand up wheelies; the rear end used to swing left and right but only a lil bit, once i adjusted the weight to the center it would ride perfectly straight.
I've seen some videos where guys are doing sitting wheelies and the rear tire moves about a foot to the left and right and pummmmmmmm they go down ; that looks scary and nasty
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pdb1964
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posted March 21, 2005 08:48 PM
frEEk, it sounds like you might of been over controlling when the rear end slide out. If you were almost straight up (no lean angle), then the back end was just swinging left and right as you over corrected when counter steering. With no lean angle, I thing CanadaMaxxer's theory (or the book theory) would work. I tend to ease off on the throttle and wait for the rear to hook up again. Again, this is almost with no lean angle. At higher lean angles, I've stayed (or tried to fight to instict to let off) on the gas and steered into the slide and hoped everything lines up again before the rear tire grabs, or the rear slowly regained traction. Although I've been riding a while, I haven't taken any racing or track courses so maybe I've been lucky so far but this seems to be working for me.
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