dampers and slappers

Does anybody know what exactly causes the oscillations in a tankslapper? Is there anything that can be done to pull out of one once it has started? I have noticed many posts about steering dampers, and how they are supposed to make a tankslapper less likely. How do they work? Are there any disadvantages (do they hinder the performance in some way) to steering dampers? Why wouldn't Yamaha, or any bike manufacturer for that matter design their bikes so that a steering damper would not be needed? Lastly, what bikes or types of bikes are the best candidates for tankslappers? I would love to see someone on a hog get a tankslapper.

If the bike is used "correct" and everything is in mint condition there's no worry of getting a tankslapper. That's probably why Yamaha a damper on their bikes. And if they would put a damper on it they would reduce sales for companies making steering dampers. If you are stunting and riding hard... then the bike will be more prone to giving you a tankslapper or a headshake. the reason a tankslapper begins is due to that fact that the wheels are not in the same line.. (when landing) this will force the wheel back to the "correct" position but sometimes with too much force and it will swing over too far on the .. otherside.. and then the same effect will happen over and over again.. this until the slapper resides or until you and your bike is down sliding on the pavement. A steering damper is what it says.. a steering damper. It makes movement of the steering harder and harder the faster the movement of the handlebars are. Oil inside the damper has to travel through a certain amount of space.. this space can most often be controlled via a knob on one end of the damper (atleast on my Öhlins). This knob adjusts the size of the hole which the oil has to travel through.. the smaller.. the harder the damper takes up steering movements. I hope you understod what I said above.. there is more to be said about Why a slapper can occur. I'll leave that to someone else to answer though.

The wheel line-up thing is what its all about. You can get a head shake from coming out of a turn with alot of throttle, and if the front wheel and back wheel are not lined up when the front and/or rear regains grip, you can get a head shake. You can see that alot in SBK and motoGP, for obvious reasons.

A tank-slapper derives from movement of the steering head from right to left lock and back.... essentially slapping each side of the tank. Headshake would be twitching of the steering head experienced before a full-blown tank-slapper. Headshake and tank-slappers or whatever you like to call 'em are basically a product of bikes with seperate forks. Essentially uneven road surfaces and ripples aswell as landing wheelies upset the suspension by slightly compressing one fork while the other fork is rebounding... something which if not rectified in short order results in a "seesaw" effect which increases the movement of the forks and the steering head. I've heard lots of conflicting advice on how to survive such occurances but it really depends on how severe they are and how quickly they progress.... however a method I've always employed if possible is to unweight the front tyre enough to let the suspension settle and then load the front a little on the landing by using a little bit of back brake.... but it seems to differ on different bikes with different suspension settings so don't quote me on that... all I know is it works for me.

Once you get a true tankslapper, there is essentially no proactive steps you can take. It's been my experience that those who argue to get on the gas to transfer weight to the rear and unload the front for the purpose of aborting a slapper once it occurs, have not actually had one. In a true tankslapper, your hands, wrists, arms, and shoulders are being wrenched so forcefully they are useless. Your thighs are pounded into gas tank and frame with great force. Your head and neck are being whipped about so violently, you can't think, or see straight, let alone think and react to the situation in a curative way. Here is a video of a true slapper at the Isle of Man: http://www.1888fastlap.com/images/TankSlap.mpeg Some bikes are more in need of a damper as some bikes are inherently more prone to a tankslapper, with steeply angled steering heads and fork tubes, with low rake and low trail specs for increased turn in speed and flickability, short wheelbases for quicker steering as well. These characteristics make a bike easier to turn, but less stable and more likely to get headshakes and in the worse case scenario, a true tankslapper, especially when you also include a high hp motor and aggressive cornering/corner acceleration, or landing a wheelie crossed up.

A big thanks to everyone that responded to my questions. Your replies were all very informative.

Originally posted by Swedie If the bike is used "correct" and everything is in mint condition there's no worry of getting a tankslapper.Swedie, That statement is simply not correct. The likelihood of getting a tankslapper or headshake is directly related to chassis geometry, suspension setup, road or track surface, and rider input. A perfectly straight bike run exactly as designed can be very prone to headshake or tankslapping. Today's sportbikes sacrifice stability for nimblness. Scott

I was going to add another statement on that... but forgot. mint condition.... + that if you ride NORMAL.. without stunting, doing the speedlimit.. etc. then there's absolutely no worry. then there are other coditions.. like road condition.. nail in tire or whatever that can contribute to a slapper or headshake.