What is a tank-slapper?

[Gazz]

And why do they happen?

Is it when your handlebars go from side to side rapidly and appear that you are punching the tank?

Or is it when you come down too hard after performing a wheelie?

Thanks

[Pete.]

It's a man-sized speed wobble.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Scutter]

I used to get them from time to time on my 1000rx, and they would scare the shit out of me. I'd hit about 90 *cough* and then maybe would catch the edge of some road surface repair etc, and the bars would start to wobble violently side to side. Just had to back straight off and try to compose myself....
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Current bike: FJR1300
Previous: SS50, GS50, TS50, GP125, NS125, GSX250, GPZ305, GPz550 81 twin shock, GPZ550 UniTrack, GSX550es, 2x GPZ600r, GPZ1000rx, v Strom 650 GT

[Eddie Hitler]

Petrol sloshing around the tank, causing a wobble. Doesn't have to be after a wheelie, can just happen.

Edit; I thought it was the fuel but there are alot more aspects to it.

https://en.wikipedia.org/wiki/Tank_slapper#Wobble_or_shimmy

[Gazz]

[c_dug]

IIRC you are supposed to power through it rather than back off as backing off just adds weight to the front.

Could be wrong with that though, never actually had a tank slapper and I've had air on my divvy at over 100mph and landed crossed up, must be much more likely on some bikes than others.
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[thx1138]

Tank slappers.

https://img.photobucket.com/albums/v616/THXII38/DSCF1895_zps99b6b722.jpg

[pepperami]

[covent.gardens]

I would have to sell any bike that was prone to that bullshit!

I accidentally wheelied the CB500 when I had a fat pillion on the back. First ever wheelie in my life. Due to inexperience/totally not expecting it, I let the bars turn in mid air so the front wheel landed crooked, and it had a mini tank slapper (in so much that it wasn't a tank slapper at all because it didn't slap the tank, but it did fast side-to-side motions). That is what I like about the CB500, on the rare occasion that I do screw up, it sorts it out for me whereas some other bikes would've made me pay big time for that I'm sure.

There are some good tank slapper compilations on Youtube.

[illuminateTHE...]

So would a damper stop such things from occurring?
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Theory: PASSED Module 1: PASSED Module 2: PASSED 12/2012!!!

yzf r125 [SOLD] sv650 [CURRENT]

[pepperami]

A damper might? stop small tank-slappers?

It will certainly help against head shakers, some jitteryness of the front end, and tiny wobbles.
But if your bike is doing those sort of things, get it sorted out!

Both my old Suzuki gt 250 and my Rd 250 lc had a light and twitchy front end?.
Both were sorted out by the addition of a fork-brace and good tyres.
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I am the sum total of my own existence, what went before makes me who I am now!

[radicalrabit]

STEERING DAMPERS reduce the effect but not if its severe

IE in the TT mentioned above. Bike 38 Paul Oritt

https://www.youtube.com/watch?v=XiKmPFo6xNA

Some times the problem is the rider who makes things worse.
The bike is basically tying to resolve its own problem to keep centripedal and centrifugal forces working keeping the bike up right and straight. You grip your bars tighter as it starts to go tits up the forces transfer to the rider the rider then over corrects as the bike has put the rider off balance.

If the rider had more grip with knees and ankles to the bike, less tightly gripping the bars, the bike would tend to recover on its own . REF TWIST OF THE WRIST II,
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VF1000 F2F, BLACKBIRD with carbs, 2nd VF1000F2F just need somewhere to go now..

[Kradmelder]

I have had head shakes on sandy roads when you hit a pile of loose sand. The best way out is sit back and give a bit of throttle.
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2011 KTM 990 Dakar
2009 BMW 1200 GS

[Redoko]

Once by accident. Never again.
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"Let's face it, this is not the worst thing you've caught me doing."
Sudika Sportsman SK50QT > Gilera DNA50 > Honda CBR125 RW7 > Kawasaki Zephyr750 > Suzuki GSXR600 > Honda Hornet CB600F '51

[Old Git Racing]

If you get a 'Paul Oritt' moment it doesn't matter, it will end badly.
For a normal slapper don't grip the bars too tight, wind it on and not back off and it should correct itself remembering to check your pads haven't been knocked back in the calipers. Easy to say, hard to do.
A steering damper will help prevent something developing that becomes unmanageable.

OGR
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2022 Tiger Sport 660 2019 Street Twin 2003 K3 gixxer 1000 1998 Srad 600 track hack

[Legsy.]

Try to avoid using the front brake on an airborne wheel..

[UrbanRacer]

This is a tank slapper.

https://www.youtube.com/watch?v=v5rhlw_f_FI

when you are in a full tank slapper like the above its impossible to do anything with the brakes, clutch or throttle.
If you try to grip the bars hard and do anything you will either end up with broken thumbs or wrists, or you will be thrown from the bike.
Your only real chance of getting out of it is try and stay loose and hope to ride it out like the above, however thats no always possible and if it happens on the road you'd probably be better bailing off the bike.

If you make it out unscathed give the front brakes a check as the pistons have a habit of going into the calipers for a sleep, remain calm and pump the front lever till you get pressure back.

[mysterious_rider]

Okay now I'll talk from personal experience here. Everyone will tell you to back off the gas or give it some light beans but you know what, if you get a REAL tank slapper you know this is impossible.. Why impossible do you ask? Because a REAL slapper will shake you so violently to the bone your feet will get thrown off the pegs, any bar mirrors you have will fly away and your clipons will smash into your tank either side. The ONLY thing you can do is hold on for dear life hoping and praying you can stay on long enough and not hit a wall or a car before it sorts itself out.

When it happened to me up a hill at 50 I dented the tank pretty bad, mushed up the steering locker tab a lil bit, and it was so bad my legs came out and I remember my foot hitting the fricking front wheel!!!!

Did eventually sort itself out, and lol's were had all round. Found my mirror too! (it was fuct)
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KAWASAKIIIII

[Tungtvann]

I normally get off the bike when it starts to do that.

[goto10]

Closest I've had was hitting a dead fox on the A130 at about 80 (unlit section going towards Swallows), I remember seeing it appear in my headlight as I was changing lanes and realising that I was absolutely going to hit it, just as I went over it the front of my bike went up and I remember two distinct thoughts run through my head - 1) How sad it was that it was curled up as if sleeping (I'm guessing it was hit by a car and curled up to die) and 2) Fuuuuuuuuuuuu...
When it 'landed' the front of the bike shimmied wildly for a few moments before settling down. At the time it felt like a tank slapper, but in reality it was probably just a bit of a wiggle. Not something I want to experience again though, my left wrist was pretty sore for a few days.
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'12 NC700S & '12 CB600F Hornet [Stolen by some dickless twat] Suzuki GT500 shed

[Snorty]

https://www.youtube.com/watch?v=SAnjjHKclZs&t=1m
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Current: Yamaha FZ1 '07 | GSXR 750 SRAD

Past: CB125TDC | TZR125 | GPZ500 | CBR600F3 | ZX9-R | GSXR1000 K4

[Tungtvann]

According to some scientific research, tank slappers can start when an ever so slight oscillation in the road surface (+/- 1 cm over many metres) acts with the speed of the bike and various other factors. I guess that's why they can appear to happen so randomly. It's like how suspension bridges would shake themselves apart in the wind or like the millennium bridge in London started wobbling with the peds walking over it.

So I read anyway.

[Ariel Badger]

I had a bad one at Loton Park click booted her out of Keepers and almost got chucked off up Cedar. I so phased me that I thought Fallow was the last corner and I ended up in the tyres at Museum thinking I was going for the line. Nothing I could do when it hit, a hideous experiance.
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[Kradmelder]

I guess if you get one on a Harley it would be a cheek slapper? which is about the height of the handle bars

I think the difference between your track or road tank slappers and off road ones is for one the speed. off road you can get them under 80 kmh, and you can fix it with some throttle, unless you hit a rut while it is going on, then you are in for a high side.

The next difference is the traction. On tar if the wheel suddenly bites you will go down. Off road you have some slide available.

I find I will get them when Im following a cage track, then the cage turned and their is a wall of sand across your path at an angle. Alternatively when you try to pull out of your line at too shallow an angle, and cut in to a pile of loose stuff at a shallow angle with too much speed.

I assume a bit of back brake may also fix it, as you change the speed difference between the 2 wheels and prvent oscillation, but I havent tried that. the times I have had it the bike righted itself before it got too severe, just by riding it out. I had ity twice on one stretch of road, which alternates from hard to loose gravelly sand.

A distinctly unpleasant experience.
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2011 KTM 990 Dakar
2009 BMW 1200 GS

[Snorty]

Weirdly I had a small "tank slapper" on a Pizza Hut moped. Still quite scary.
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Current: Yamaha FZ1 '07 | GSXR 750 SRAD

Past: CB125TDC | TZR125 | GPZ500 | CBR600F3 | ZX9-R | GSXR1000 K4