Stop me getting slapped

Tankslappers - Why?

I've had a couple, the last one was nasty (see topic - which bike?). What causes them? They're a bit of a worry, I've had a look at the road and it seemed pretty smooth. I hadn't had the bike for long, but I'd nailed it in second plenty of times without so much as a shake, but for some reason, this time it decided to do it's impression of a rodeo bull.
In this period while I wait to see if my bike is repairable I find myself thinking how I can make sure it doesn't happen again, but I keep coming up blank. A steering damper could be the way to go, but there are plenty of bikes out there without them, so why does this not happen more often? Maybe if I understood the mechanics of the tankslapper a bit better I could have the confidence to ride without the fear of suddenly being spat off.
Can anyone help?

I'm a newbie, sorry. What is a tank slapper?

Thanks...

Originally Posted by thor

I'm a newbie, sorry. What is a tank slapper?

Thanks...

ditto

And I take it your trying to go forwards at the time too? Bugger...

Originally Posted by leesimons

A tank slapper is when the bike's bars go from lock to lock (full lock one way, to full lock the other way) very quickly and uncontrollably.

Not good!

Luckily not experienced that

i used to get the front wiggle alot on my naked when i accelerated hard. it didnt go from full lock to full lock, but it was enough to scare the crap outta me.

Just found this on MCN website:

TANK slappers can occur when accelerating hard in a straight line, accelerating hard out of a corner or landing wheelies.

There are two schools of thought about surviving tank slappers; accelerate more or accelerate less. More throttle should unload the front wheel and thereby calm the steering. Less throttle should put more weight on the front and hopefully overwhelm the wobbles before they develop into a full-blown lock to lock slapper.

Don?t apply the brakes, just hang on. There is rarely any time to develop a conscious plan, but the best way to survive them is to avoid circumstances that tend towards them, such as landing crossed up wheelies.

Doesn't explain WHY tho...

They are caused by the wheel getting knocked (by a bump for example), making the bars slap from side to side. As lee said, they usualy happen under hard acceleration on bumpy roads. This is because under hard acceleration the front goes light, so it's easier to knock the wheel when there is little weight on it. Sporty bikes are most prone to this because they tend to have quick steering geometry and a power to weight ratio that means it's easy to lift the front.

Poorly setup rear suspension also contributes, I seem to remember reading as well.

More info, and a video here: http://www.joe250.com/motorcycles/ride/tankslapper.htm

well, i was nailing it in second, so the front would have been light for sure. i had a slapper on the old sv, but kept it nailed and it sorted itself out, it turned out i had completely the wrong tyre pressures. but this one seemed to get very big very quick. like i said, i didn't have the bike long, so maybe the rear suspension wasn't set right for me. that's the only thing i can think of so far.

i'd be happy to have a bike that didn't do it. it's a big worry for me now.

for the noobies, here's a classic one:
http://www.bikepics.com/movies/000464/

From about.com forum, i thought it summed it up well.

tankslapper- a rapid, high intensity oscillation of the handlebars (literally, slapping the tank side to side). It is a condition of dynamic instability, such as hard acceleration out of a bumpy corner. Classic case would be the rider landing a botched wheelie with the handlebar/front tire turned instead of straight and square.

I saw a problam about them not long ago, the conclusion was they don't exactly know why, and can't really do anything about it.