What causes a tank-slapper?

[BadDog]

Is it when you hit a bump under power and your front wheel lands slightly at an angle?

Had a pretty serious one the other night.
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VFR400 NC30 > Kawasaki ZX6R > YAMAHA YZF-R1 > Moto Morini Corsaro Veloce

[extreme3d]

[colin1]

yes it happens when your front wheel come off the ground and isnt straight when it comes down
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[extreme3d]

They can also be induced by having poorly set-up suspension.

[Misc]

So if you was doing a weelie at high speeds & landed the front wheel at a angle?

[BadDog]

[BadDog]

[Dark]

I've also been led to believe that if your fork angle is too steep, under hard acceleration your front wheel will tend to be deflected sideways wanting to around the bump in the road rather than over it.
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My Bikes in order:- Yamaha RXS100 / Suzuki X7 250 / Yamaha RD350LC / Kawasaki
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[paulthewitt]

a tankslapper:

"high frequency oscelations of the front wheel"

generally caused by hitting a bump under hard acceleration. or landing a wheely crossed up. thats pretty much all i know (other than to get out of em you should accelerate hard and stay loose)

Paul

[BadDog]

[Kickstart]

Hi

Big difference between the bars going lock to lock when the front wheel hits the ground slightly off straight and a proper tank slapper.

Proper tank slapper might be trigger by that, is essentially caused by the bars going lock to lock (or close) at there natural resonant frequency, so they just keep doing it. Often the only way out of it is to accelerate hard, but most people will just get thrown off instead.

The bars will oscillate with a hell of a lot of force. Quite easily enough to injure you if you try and hang onto them hard even before you fall off.

Fortunatly they are very rare these days.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Dark]

[Kickstart]

Hi

I would very much doubt they are true tank slappers. If they were there would be ZX10R riders queued up outside every casualty unit in the country.

Light steering and the tendancy to go lock to lock occasionally are quite likely.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Dark]

Fair point Kickstart. It just seemed that way stepping off a 7R onto a 10R.
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My Bikes in order:- Yamaha RXS100 / Suzuki X7 250 / Yamaha RD350LC / Kawasaki
KR1S 250 / Kawasaki ZXR750 H2 / Honda C50 / Kawasaki ZX7R P5 / Kawasaki ZX10R / Suzuki GSXR 400 / Honda CBR1100 Blackbird & Yamaha FZR 600

[Walloper]

Like a 'thigh slapper' but not as funny
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W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[bish777]

70's and early 80's bikes are well known for tankslappers.

Later bikes are better and more recent machines are much much better.

My GSXR 1100 wobbles and threatens to tankslap under hard accelleration, but never does.
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GSXR1100J

[mr.z]

Its also geometry, youre not likely to have a chopper tank slap, but something like a tl1000 was known for then (unfairly probably)


Allot of the problem with them is the riders natural "hang on for dear life" response, the movement from the bars is transfered through the rider to the rest of the bike = you're goin down!

[bish777]

[Kickstart]

[Jack_Cheese]

I wonder how bad buells are for tank slappers - the rake on them is rediculously steep, and the trail is minimal. I hope that i never have a savere tank slapper - i think i'm more likely to highside lol.

Jack
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[Chriss]

I don't know if it's a tank slapper or not, but under harsh braking (when someone pulled out on me whilst I was on a roundabout) I expierenced lock to lock steering and was only stopped by the fact I stopped (hit the car). Shouldn't happen again, I got a steering damper.
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TheShaggyDA: I've got 3 or 4 pairs that predate my wife, so at least 11.5 years old.

[stinkwheel]

Well I would have said that the most common cause of a tankslapper is not having enough air pressure in your back tyre, closely followed by having an unaccustomed amount of weight on the back of the bike (like a pillion).

The GPZ has shaken its head on numerous occasions, sometimes quite violently, especially if you gas it on a worn front tyre and hit a pothole/cats eye. Stayed on it OK. Maybe my short time spent riding a combo got me used to the bars shaking lock-to-lock without anything too drastic happening (which it wont if you don't panic and keep the throttle open).
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[instigator]

Steering dampers are wonderful things.

Never had an upset in 2000 miles on the sv. With the damper, it has the ability to handle like an sv should....

or

like a bus.

Good fun finding the right setting.

Will always get one on my future bikes now.

[sanchezz_182]

i made a thread not so long ago about my tank slapper thing, cant find it thought..

only every had one on the cbr after hitting a bump in the road that fired the bike at an agnle at 90mph, sumhow i kept the bike on the road. next day my sholders an left ankle wer pritty stiff.

after alot of speculating (sp) i decided that it was the road that cused it, although my head stock bearings had just been greesed up so was lighter that usual,
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[Knowlsey]

thought a tank slapper was a dirty bitch taking it from the rear over the tank, now i am confused