A question

mohawk miss · Post by **mohawk miss** » Wed Apr 05, 2006 4:10 pm

Okay, I'll admit to not being a very experienced rider. :roll:

What I would like to know is, how does a bike 'develop' a tank slapper?

And how do you recover the bike ( if possible)? And I'm talking roads here, not track.

Thank you for educating the curious.

mick_dundee · Post by **mick_dundee** » Wed Apr 05, 2006 4:17 pm

My bike "developed" into a tank slapper after getting anew front tyre fitted at a Kwaka dealer in Melbourne that will never see my business again.

For me to recover I just throttled off momentarily and put my hands back on the handlebars, recovery will depend largely on rider experience, speed, conditions you're riding in etc I suggest.

Note that this isn't the 'only' way tank slappers can develop but that's how it happened to me, fixed the problem by crashing into the mud cliffs in st andrews and needing a new front wheel and tyre, probably not the "ideal" way of fixing these things, in fact it's a rather drastic way of doing it to be honest...

Glen · Post by **Glen** » Wed Apr 05, 2006 4:17 pm

Don't know the physics behind it but essentially you hit a bump or something on the road (or your front wheel comes down turned after a mono) which forces the bars one way. Either the bike, but usually the rider overcorrects and pushes the bars back the other way. The same thing then happens in reverse with the "slaps" getting bigger until you meet your eventual doom.

If you can do it, get on the gas to get weight off the front, easier on a ZX10 than a 250 granted but it will cure it. The best cure is prevention though. Ride as loose as a goose and go with the flow. Nice and light on the bars and let the bike sort the shit out. It inherently wants to go in a straight line and usually if you let it do its work it'll be fine.

Frank · Post by **Frank** » Wed Apr 05, 2006 4:19 pm

Have a look at this

http://www.handleitorloseit.com/wobble.html

z900/zx9 · Post by **z900/zx9** » Wed Apr 05, 2006 4:22 pm

Yep power on smoothly if possible and as previously said dont tense up.If you want to practice tank slappers and bike wobbling around corners at speed go have a ride on a z900 :lol:

ZX10R King · Post by **ZX10R King** » Wed Apr 05, 2006 4:58 pm

Ask Hemi, he knows all about tank slappers

:lol:

mohawk miss · Post by **mohawk miss** » Wed Apr 05, 2006 5:57 pm

so you speed up? Natural inclination would be to back right off (for me, probably letting go of the throttle altogether). That makes it worse?

Tones · Post by **Tones** » Wed Apr 05, 2006 6:09 pm

Tis not an easy one to answer as it depends on what the cause is. Generally speaking most modern bikes are designed to not get into a tank slapper, however that doesnt mean they dont happen. What a tank slapper as far as I know is an oscilation of the the steering. I am not into physics enough to know a lot about this. But I do know the cause is most often related to the centre of gravity and the tyres. The tyre can be the cause if not inflated to the correct pressures, but the biggest cause is suspension. That is to say a shock is not doing its job or is badly worn, or the suspension has been adjusted to changet he centre of gravity and move it backwards or forwards. Sometimes peopel drop the forks in the tripple clamps to lower a bike and this changes the steering head angle. Changing the trail and rake on a bike can have disasterous consequences. My advice would be to see a reputable suspension expert as they know what the causes are and what is the best way to fix it. So many causes exist out there, and how to "ride through" them depends on what the cause is.

Cheers

Aussie Ninja · Post by **Aussie Ninja** » Wed Apr 05, 2006 7:29 pm

Have managed to avoid a full on slapper so far, but my bars have given the occasional twitch when I'm right under it in first so there is no weight on them when they hit a road imperfection. They also waggled on me once when landing a power wheelie in first without the bars 100% straight. I was too busy being chuffed I'd got the front up. :lol:

I-K · Post by **I-K** » Wed Apr 05, 2006 7:40 pm

mohawk miss wrote:so you speed up? Natural inclination would be to back right off (for me, probably letting go of the throttle altogether). That makes it worse?

Yes. Backing off in reaction to a tankslapper is about as counterproductive as you can get.

A tankslapper essentially feeds off the energy stored in the front springs (and the deformed front tyre, for that matter). Back off and there's a weight transfer onto the front end, causing the front springs to compress further, which pumps more energy into the tankslapper.

Gosling1 · Post by **Gosling1** » Wed Apr 05, 2006 9:45 pm

mohawk miss wrote:....And how do you recover the bike ( if possible)? And I'm talking roads here, not track.....

* Keep on the gas - do NOT back off.

* Keep both hands on the bars.

* Do NOT panic, as already pointed out, bikes naturally want to go straight, as soon as you are past the shitty bumps that caused the tankslapper in the first place, you will be OK.

My old Z1000 once did a couple of full lock-to-lock tankslaps at >160kmh, over some shitty bumps on the New England Highway many years ago. Once the bumpy patch was gone (about 2 seconds later), the slaps were gone, and the bike just continued to track straight....

Normally, a proper tankslapper is *exactly* that, your bars travel from lock-to-lock, not just a slight wiggle over some little bumps.....thats just a slight wiggle... :wink:

Nanna10r · Post by **Nanna10r** » Wed Apr 05, 2006 10:44 pm

What about the rear end slip, grab Bitch slap tank slappa fella's ?, don't forget them they are harder to manage then the front end ones imho.
Been some great advice about front end Slappa's.

I'm sure "Vegie Slappa" Hemi, will be along any minute to tell you about the best tank slappa I've ever seen. :lol:

The Bugger didn't even slow down kept it pinned & tossed into into the 1st corner at Morgan Park by the time i realized i was going to run over a cartwheeling "barra" he was goooooooooooooooooooooone.

Cheers Brett

SnypR · Post by **SnypR** » Thu Apr 06, 2006 12:03 am

i had one just the other day. Came around a left hand corner, knowing a trainline crossing in there. Thought l would open it up while still slightly leaning, hit the first bump which went straight into a tank slapper. Before l knew what was happening, l held on firm and just opened it up even more. Fixed itself like the others have metioned and l like to think that l didnt crash because l knew in the back of my mind what had to be done.

Had the same experience when leaning over in a bend and hitting gravel, front wheel slipped out and some how l pushed off thin air to bring the the front wheel back inline.

mohawk miss · Post by **mohawk miss** » Thu Apr 06, 2006 12:03 pm

Thanks for the info, finding this very informative, esp Tones and Gosling1.

So, you can also get one from the rear of the bike as well? Does then the opposite apply, in that you would slow to transfer the weight to the front?

As a newish rider I was a bit spooked by an incident last sunday, and I would like to be prepared should this misfortune happen to me. :cry:

Neka79 · Post by **Neka79** » Thu Apr 06, 2006 9:29 pm

mo....ever noticed that centrifical force makes the bike harder to turn at higher speeds??
its requires more force to tip a bike in at say 120kph than it does at 40kph.....
once ur wheels are spinning, the faster they go, the harder to fall over..hence why when u take ur hands off the bars at say 120kph its easier to keep the bike steady than at say 40kph...

(this is also why sum guys can do wheelies that look like there going to wobble themselves off to the side, but they pull it together- edit see NEKA)

this is why u stay on the throttle (also as IK says abt loading the front forks if u back off) but also the centrifical force will help u pull out of it if u stay calm & on the power....

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