Tankslappers explained

[Riff Raff]

Shamelessly stolen from www.sportrider.com

1. The “tankslapper” is a very frightening experience. Usually occuring when accelerating hard over bumpy pavement, a tankslapper ensues when the front tyre becomes airborne, then regains traction outside the rear tyre’s alignment. The resulting deflection bounces the tyre off to one side, followed by another bounce in the opposite direction as it contacts the pavement again. Unless the bike’s steering geometry is able to damp out the deflections quickly, the resulting oscillations from the front tyre as it bounces back and forth will swiftly gain in strength, causing the bars to swap from side to side with increasing ferocity. The oscillations can be violent enough to rip the bars out of your hands, and fling your feet off the pegs. You can guess what happens next.

2. The easy cure for this problem is a steering damper. Many sportbikes now come stock with one, as the radical steering geometry needed for quick handling can otherwise cause some instability in certain situations. While a steering damper is an easy fix, it shouldn’t be a cure-all; if you’re forced to adjust the steering damper’s stiffness (if available) until you can barely turn the bars in order to keep the bike’s handling stable, there is a problem somewhere in your chassis setup. A too-stiff steering damper can also cause handling problems by itself; if your steering damper is adjustable, and you find that your bike won’t hold a line (especially in slower corners), or gets into a small wobble or oscillation in high speed corners, try backing off the stiffness a little and see if it helps.

3. Not all sportbikes need a steering damper, however. Many have steering geometry setups that offer quick handling, while still providing the necessary stability to damp out any front-end oscillations. In most cases, one of the biggest contributors to a tankslapper is your body positioning and grip on the bars. Some people ride in a more upright position when carving corners, but when accelerating over bumpy pavement, that upright body position puts even more weight transfer to the rear, which causes the front end to get lighter. Also, the more upright torso means that your grip on the bars is tighter in order to stabilize your upper body. That firmer grip feeds more input into the front end, something it doesn’t need while it’s busy trying to damp out the inputs from the bouncing front tyre. It actually forms a vicious circle: you grip the bars tighter because they’re starting to flap back and forth, but that only feeds more input into the front end, compounding the problem further.

4. The easiest way to avoid tankslappers while accelerating over bumpy pavement is to—believe it or not—keep a relaxed grip on the bars. Relaxing your grip on the bars means you must lean forward in order to assist in keeping your torso stabilized. This helps put more weight on the front end, which keeps the front tyre on the pavement. Since you’re not using your arms to stabilize your upper body, get your weight onto the footpegs so that you can get your body as far forward as possible; this also allows you to grip the tank with your knees for more stability.

If you do get into a tankslapper, keep your weight forward and—as hard as this sounds—maintain a relaxed grip on the bars. Let the motorcycle’s chassis deal with damping out the oscillations. Don’t try to be a human steering damper; you’ll only make the problem worse. Tankslappers can definitely soil your undies; but if you’re able to deal with them correctly, you’ll usually ride through them before you know it.

[Blackbird]

Nice post. All of it true too. Had a beaut this year whilst passing a car and it slapped so badly that I couldn't actually hold the bars properly but as you correctly say, it just sorted itself out. I had to sort out the brown undies myself:sick:

[Lou Girardin]

Probably the most frightening thing a bike can do. You're usually just a passenger waiting for the splat.
I had an old CB750 start slapping at around 140 km/h, I managed to get it down to around 100 - 110 before it spat me off and destroyed itself.
I clearly heard the front tyre chirp as it went from lock to lock.

[oldrider]

Well done. Tankslappers are like your first nookie, they sneak up on you when you are least prepared for it.
Same sort of effect too when you think about it.:blip:
So far so good on both counts, sadly only got the tankslappers to worry about these days! :shit:

[jonbuoy]

He he, never had a full on lock to lock slapper, a few shimmies and shakes but heres how NOT to handle one.... Crossed up wheelie landings can trigger em too.



http://www.bikepics.com/movies/000464/

[The Stranger]

Well done. Tankslappers are like your first nookie, they sneak up on you when you are least prepared for it.
Same sort of effect too when you think about it.:blip:
So far so good on both counts, sadly only got the tankslappers to worry about these days! :shit:

Um... What exactly did you have your first nookie with?

[Motu]

I had my first tankslappers at speed on the beach.They are horribly ferocious,more so than on the road - sand builds up in front of the contact patch and slams the forks onto the stops with a clang...once I had to stand on the pegs and let the bike gyrate beneath me,you just couldn't stay in that place.The only plus is that it's a softer landing in the sand...but I was never spat off.

I decided I had better retire my old XS1 when I had a major tank slapper at 150kph coming up the hill from Riverhead Forest to the gun club.So I go back a month later on my superb handling XLV750 - and had another tank slapper at the same speed on the same corner...so it wasn't the bike after all!

[RiderInBlack]

So with "Roxanne" being such a front heavy bike, would this be why I bare have had even a hint of tank slap from her or are Honda steering geo. just fu*ken good? By the way even by cracking the throttle full open on her, she barely lightens the front end.

[SwanTiger]

I had a tank slapper on a pitbike ! heaps of fun.

[Patrick]

No, No... don't do this to me...

I always thought a tank slapper was a loose/good time woman who likes sex on the tank of a bike...

That is what I still want to think... and it happens lots...

Soulds like much more fun than what is posted above!!!!

[Ixion]

One of the relatiely few things on bikes that scare the shit out me. Classic "deal with" is to keep power lightly on, shift weight forward until it damps itself out. Easier said than done!

(Always a good idea to have weight forward on exit from a corner BTW - helps with the dreaded slapper, and helps keep the front end down. Of course, you may pay for that with the rear wheel breaking away if you are too heavy handed on the throttle. Sigh. No such thing as a free luinch, but I'd rather have the rear misbehave than the front)

I've only had a couple of true tankslappers (as opposed to heavy steering wobble and weaving), could very happily live with never having another.

I reckon that it's about the nastiest thing out on a bike. And always happens at speed.

Impossible to induce for training purposes , either.

[DemonWolf]

Patrick.. does your wife know of your.. interpretation of a Tank Slapper are?

[Motu]

Nearly all sidecars go into a shimmy at 35mph (sorry,sidecars are very Bwitish y'know).One of my chairs was good hands off - but I'd give the bars a smack and sit back and watch it shake smacking the steering stops,then I'd just touch the bar and it'd stop.But trying to teach my wife to ride my big outfit it'd go into it's shake,and she'd freak out thinking she was in a tankslapper - understandable I suppose as she had consusion once from being spat off in a tankslapper.

[RiderInBlack]

understandable I suppose as she had consusion once from being spat off in a tankslapper.Things we did not need ta know about Motu's husbandly practices:gob: Hope ya at less had the garage door closed at the time (just teasing ya Motu).

[kickingzebra]

Whoa! your wife is a legend Motu!!

[Mental Trousers]

So with "Roxanne" being such a front heavy bike, would this be why I bare have had even a hint of tank slap from her or are Honda steering geo. just fu*ken good? By the way even by cracking the throttle full open on her, she barely lightens the front end.

All that weight on the front is a major contributing factor to not having a slapper. The other is that your bikes steering geometry is fairly conservative - the more radical it is the more likely it is to suffer from tank slappers.

[RiderInBlack]

The other is that your bikes steering geometry is fairly conservative - the more radical it is the more likely it is to suffer from tank slappers.Could ya define what ya mean by "conservative" and "radical" steering geo. Are ya talking fork angle and length here?

[Buster]

Owned three RGVs, All produced the dreaded tank slapper. Some of them were actually nice ladies..(pt) Apart from that I dont think theres much option than just hold on and be a passenger. Best thing to try is dont let your legs fly around. Grip them to the tank. Throttle control is useless. When it goes lock to lock you wont be able to use your thumbs for a week.

[The Stranger]

The steeper the fork angle the shorter the trail.
The shorter the trail the less castor effect.
The less the castor effect the greater the propensity to tank slap.

Weight plays it's part too and shorter wheelbase bikes tend to unload the front easier. Shorter wheelbase bikes tend to be more agile also so this is often a goal. One way to shorten the wheelbase is to steepen the forks.

So a modern sport bike, which tends to have a steep fork angle, a short wheel base, is light anyway and has plenty of power to unload the front wheel is more likely to exhibit the problem than yours.

[Mental Trousers]

Could ya define what ya mean by "conservative" and "radical" steering geo. Are ya talking fork angle and length here?

Radical = steep angle on the steering axis and low trail

Imagine a line that goes down the centre of the steering head bearings. The more vertical that line is the more radical the steering geometry. Conversely, the less vertical it is the more conservative it is. Same with trail. Less is more radical.

[RiderInBlack]

Thanks Dudes. I thought that was what ya were talking about, but was just making sure. Plus some of us less bike-tech types would like ta know want ya mean too.

[oldrider]

Um... What exactly did you have your first nookie with?
Can't remember. It was over before it began! (Kevin bloody Wilson) :bye:

[Patrick]

Patrick.. does your wife know of your.. interpretation of a Tank Slapper are?

She wont play:crybaby:

[Lou Girardin]

No, No... don't do this to me...

I always thought a tank slapper was a loose/good time woman who likes sex on the tank of a bike...

That is what I still want to think... and it happens lots...

Soulds like much more fun than what is posted above!!!!

Does it end with you falling off?

[Patrick]

Does it end with you falling off?

Thatmight hurt... getting off perhaps?

[NC]

Did anyone else get flashbacks while reading that?

[Patrick]

Yep... you're in the Matrix... take the blue pill...or was it the red one???

[Crasherfromwayback]

Impossible to induce for training purposes , either.
For training purposes, just use a TL1000s with no steering damper and only around 26psi in the front tyre.
Works every time....

[loosebruce]

For training purposes, just use a TL1000s with no steering damper and only around 26psi in the front tyre.
Works every time....

Oh and be sure to be slightly crossed up when landing 160kph wheelies, works a fkn treat that does. :crazy:

Gotta love TL's, Death INC's prolly got the scariest slapper on a TL story i
ve heard (that he walked away from).

[Crasherfromwayback]

yeah mate...gotta love it when they're nasty enough to force the pistons back into the calipers!

[Two Smoker]

yeah mate...gotta love it when they're nasty enough to force the pistons back into the calipers!

hehehe i still have fond memories of that on my ZXR400.... have a lock to lock tank slapper, tyre screeching at each lock... Thanking god i didnt arse of, go to grab a handfull of brake for the esses "Ah fuck no brakes...."

As for the TL.... as bruce said... Death has the best story... I loved that TL Bruce... shouldnt have sold it man...

[Crasherfromwayback]

I know what you mean mate....I had one like that on the first demo we put on and nearly binned it big.
Had to go home for new scuddos.

[loosebruce]

I loved that TL Bruce... shouldnt have sold it man...

I fkn loved it too mate, almost more than the GSXR, maybe more, it was a wicked bike, espesh my one lol, but it loved my wallet, and the engine was showing signs of the abuse, wonder if it's still alive? God bless TL's :rockon:

[Morepower]

At my age I would be happy with a slapper :bye:

Not that sort huh ???

had a couple on the TL but only one had me scared , the steering damper takes care of em . Its a lot tamer without the rotary door closer thing that was supposed to control the suspension.

The theory in the first post is correct though , look at how many bikes carry on straight ahead after they have tossed thier rider.

[DirtMad]

Awesome thread, thanks for the info! ;-)

[sugilite]

I know what you mean mate....I had one like that on the first demo we put on and nearly binned it big.
Had to go home for new scuddos.
Did'nt stop ya telling me to take it for a test ride with a near empty tank of gas ya bastard!:nono:
I took it up Mt Victoria, and ended up having a wild slapper whilst passing a bus load of japanese tourists! They got a prime view of that bike doing it's best to spit me as I rode past their bus!

[Crasherfromwayback]

Did'nt stop ya telling me to take it for a test ride with a near empty tank of gas ya bastard!:nono:
I took it up Mt Victoria, and ended up having a wild slapper whilst passing a bus load of japanese tourists! They got a prime view of that bike doing it's best to spit me as I rode past their bus!
You like it rough mate.....

[sugilite]

Was that you I saw the other night on a street corner with your hydraulic dampner hanging out your pants hoping to attract slappers?

[jonbuoy]

Not many bikes seem to have a rep for doing it nowadays. ZX10R without damper and CBR600RR are the only ones I've heard about that will if provoked.

[Crasherfromwayback]

Was that you I saw the other night on a street corner with your hydraulic dampner hanging out your pants hoping to attract slappers?
Yeah, but I wasn't wearing any pants!

[terbang]

Great thread and I have only ever had one occasion. Got a bit smart with me old bandits suspension. Grafted a Gixxer shock into the rear and Dropped the front which sharpened the steering up a real treat. Just when I was thinking that you really could make a silk purse out of a sows ear, an exit from a 55 kay bend, over a hump giving it shit, saw me recieve a real ugly tank slapper that I survived mainly by good luck than skill.

[Falconer]

Cruising back from the Brass Monkey south of Palmerston, noticed a glassy patch on the road, running straight and smooth at 90k, then all hell broke loose. The revs built up (wheel spin) and the BMW R80 took of sideways big time. Back of power to a violent tank slapper.Side to side for about 8 slaps and slowly came straight. Holly heck, if this is the joys of motor cycling you can stuff it. Totally unprevoked probible cause a patch of diesel,The weather was misty, damp, no rain, cold. My first big one. Riding for 50 years. Is it tme to sell my bike? :eek5:

[chanceyy]

Cruising back from the Brass Monkey south of Palmerston, noticed a glassy patch on the road, running straight and smooth at 90k, then all hell broke loose. The revs built up (wheel spin) and the BMW R80 took of sideways big time. Back of power to a violent tank slapper.Side to side for about 8 slaps and slowly came straight. Holly heck, if this is the joys of motor cycling you can stuff it. Totally unprevoked probible cause a patch of diesel,The weather was misty, damp, no rain, cold. My first big one. Riding for 50 years. Is it tme to sell my bike? :eek5:

sorry that one just really cracked me up, is there some benefit to being female ? as it only seems to be guys posting ..

[Goblin]

sorry that one just really cracked me up, is there some benefit to being female ? as it only seems to be guys posting ..
Only benefit to being female when tankslappers occur is we dont have those extra bits to get squashed:blip:
I had my worst ever tankslapper on my Impulse. Was overtaking some big pajero or something when I hit some munted tarseal and the bike wobbled so violently under me the petrol tap went straight into my knee cap! OUCH! The pain was intense & I thought my knee was broken.
Last year when I had my mates ZZR1100 with a squared off rear tyre I came over a bumpy bridge on a corner at about 120 when it tried to break loose & spit me off. The rest of the trip to Gisborne my wrists were rather tender.

[xsive-rider]

Cruising back from the Brass Monkey south of Palmerston, noticed a glassy patch on the road, running straight and smooth at 90k, then all hell broke loose. The revs built up (wheel spin) and the BMW R80 took of sideways big time. Back of power to a violent tank slapper.Side to side for about 8 slaps and slowly came straight. Holly heck, if this is the joys of motor cycling you can stuff it. Totally unprevoked probible cause a patch of diesel,The weather was misty, damp, no rain, cold. My first big one. Riding for 50 years. Is it tme to sell my bike? :eek5:

i had an old gs 850 a few years ago, was comming back from wanganui to napier.
was on a long straight a slight drizzle just started, more of a mist really, decided to pass this big hotrod van towing a car trailer, as i get up beside him at about 130k my back end tried to overtake me! i corected it to find my arse passing me on the other side.
this carried on for what seemed an enternity, the bars were almost hard lock from side to side now with a big very tight corner aproaching fast.
it was either the 9 wire fence and into the paddock at the end or lay her down and take the corner.
i new i did not have a shit show of making the bend but went for it, you know as soon as i laid her into the corner, as greasy as it was the bike came good, around she went!!!
it was a slow ride home in the rain from then on....shit!!!!!! i thought i was dead.

[MVnut]

Tankslapper...what's that. I grew up on great handling Kwakas like H1s, H2s, Z1s etc lol:shit:

[Roj]

He he, never had a full on lock to lock slapper, a few shimmies and shakes but heres how NOT to handle one.... Crossed up wheelie landings can trigger em too.



http://www.bikepics.com/movies/000464/

Cool movie, never had the problem myself, but then I think I ride somewhat tamer than I used too:yes:

[Roj]

Radical = steep angle on the steering axis and low trail

Imagine a line that goes down the centre of the steering head bearings. The more vertical that line is the more radical the steering geometry. Conversely, the less vertical it is the more conservative it is. Same with trail. Less is more radical.


the ZEN of steering, less is more:dodge:

[Shaun]

Just another 2c worth

After racing for over 21 years now on the track and pure road courses, I have had a Shite load of the infamous tank slappers

I discoverd by fluke and practice the best way for me to deal with tank slappers

I have always applied the rear brake and kept the throttle pinned, this soughts them out very very quick! Now this goes against what most have said in here about moving your weight forward, because appling the rear brake takes the weight of the front wheel and transfers it to the rear?

My logic to my theory/Practice is this, if your bike is tank slapping and you move your weight forward, you are putting a heck of a lot more load on the front wheel which will make it bump stear more on the road service and you will have to ride it out untill the chassis can catch up and deal with it, but if you were to apply the rear brake and take some load of the front tyre, you now have the time to take control of the front wheel and stop the slapper from getting worse.

Always worked for me

[onearmedbandit]

Cheers for the heads up Shaun. Piece of info that might save someones life one day.

[Shaun]

Cheers for the heads up Shaun. Piece of info that might save someones life one day.




Deffianately worth trying, I swear it has saved my arse on many accasions, I had a slapper at Manfeild many moons ago that buckled the front wheel so bad that the bike could not be pushed, both the stearing stops were smashed off, and the petrol tank had dents in both sides of it, and I did not crash!

[Jimmy B]

Just another 2c worth

After racing for over 21 years now on the track and pure road courses, I have had a Shite load of the infamous tank slappers

I discoverd by fluke and practice the best way for me to deal with tank slappers

I have always applied the rear brake and kept the throttle pinned, this soughts them out very very quick! Now this goes against what most have said in here about moving your weight forward, because appling the rear brake takes the weight of the front wheel and transfers it to the rear?

My logic to my theory/Practice is this, if your bike is tank slapping and you move your weight forward, you are putting a heck of a lot more load on the front wheel which will make it bump stear more on the road service and you will have to ride it out untill the chassis can catch up and deal with it, but if you were to apply the rear brake and take some load of the front tyre, you now have the time to take control of the front wheel and stop the slapper from getting worse.

Always worked for me

Thats very interesting Shaun, whats your opinion with respect to linked brakes eg Blackbird X11 et al?

[The Stranger]

Deffianately worth trying, I swear it has saved my arse on many accasions, I had a slapper at Manfeild many moons ago that buckled the front wheel so bad that the bike could not be pushed, both the stearing stops were smashed off, and the petrol tank had dents in both sides of it, and I did not crash!

As a matter of interest, was there a steering damper on that bike at the time?

[Blackbird]

Would someone please describe the difference between a tankslapper and a headshake as I thought it was the same thing but apparently not according to some of the UK Blackbird website members. I was riding up to Coromandel in drizzly conditions about a month ago on the back road between Matamata and Te Aroha. I came up to a country crossroads in second or third and as there was nothing coming, accelerated over it with what I thought was a whiff of throttle. The back end whipped sideways with such speed that one of my feet came off the pegs and when it whipped back in the other direction, the end of the peg drilled me in the calf so hard that I had sweat trickling down my face. Anyway, whilst all this was going on, I got a really bad weave with the bars fluttering back and forwards. It was only good luck that I stayed on. This was what the guys called head shake which is not a tank slapper according to them.

Any comments?

Incidentally, I got to Coro and could hardly get off the bike. There was a wee mark on my calf where I'd been hit but 2 days later, my foot was all the colours of the rainbow. Internal bleeding I suppose:shutup:

[Finn]

Here's some tank slappers and as Shaun says, tapping the rear will sort em out.

[Blackbird]

Here's some tank slappers and as Shaun says, tapping the rear will sort em out.

I have as much chance of coping with them as I did with my problem but thanks for the memories:bye:

[Shaun]

Would someone please describe the difference between a tankslapper and a headshake as I thought it was the same thing but apparently not according to some of the UK Blackbird website members. I was riding up to Coromandel in drizzly conditions about a month ago on the back road between Matamata and Te Aroha. I came up to a country crossroads in second or third and as there was nothing coming, accelerated over it with what I thought was a whiff of throttle. The back end whipped sideways with such speed that one of my feet came off the pegs and when it whipped back in the other direction, the end of the peg drilled me in the calf so hard that I had sweat trickling down my face. Anyway, whilst all this was going on, I got a really bad weave with the bars fluttering back and forwards. It was only good luck that I stayed on. This was what the guys called head shake which is not a tank slapper according to them.

Any comments?



Incidentally, I got to Coro and could hardly get off the bike. There was a wee mark on my calf where I'd been hit but 2 days later, my foot was all the colours of the rainbow. Internal bleeding I suppose:shutup:


Head shake/Tank slappers, they really are one in the same. Head shake is really only the beggining of a good tank slapper. What you have described is more like a tank slapper to me

[Shaun]

As a matter of interest, was there a steering damper on that bike at the time?


No mate, just the good old arms

[Shaun]

Here's some tank slappers and as Shaun says, tapping the rear will sort em out.



Do you have any contact details for the tapping to be done?

[Ixion]

Weaving , with bars shaking or fluttering can happen on any bike. That's head shake, and provided the rider doesn't panic the shake will normally dampen down and disappear of its own accord.

However, occasionally (some bikes being much more prone to it than others), the inherent flexing frequencies of the frame coincide with the vibration of the shake.

If that happens the frame flexs with the shake, that intensifies the shake, which causes more flex which intensifies the shake which causes more etc etc . This causes the "shake" to build up very quickly to the point where it has colossal strength. Usually it will rip the steering stops out and smash the forks into the tank (hence the name) , before highsiding the rider when the wheel twists through 90 degress.

So, essentially a tankslapper is an uncontrollable dynamically amplified head shake, that, unlike a normal head shake, does not stabilise.

[Shaun]

Thats very interesting Shaun, whats your opinion with respect to linked brakes eg Blackbird X11 et al?


Only my opinion!

I hate the linked break thing, I really believe that the rider should be in controll of there own destiny, but I also hate ABS systems, you cannot stop as quick with ABS as you can with a normall system

[Ixion]

..

I discoverd by fluke and practice the best way for me to deal with tank slappers

I have always applied the rear brake and kept the throttle pinned, this soughts them out very very quick! Now this goes against what most have said in here about moving your weight forward, because appling the rear brake takes the weight of the front wheel and transfers it to the rear?

.

That was pretty much the accepted wisdom back in the day when they were common on road bikes. Pin the throttle and stay away from the front brake, keep the front end light.

EDIT. Since the true slapper only occurs when frame flex coincides with shake frequency (or harmonics thereof), probably any major redistribution of wheel load or weight may change the frame flex frequency enough to break the amplification cycle. So all those things may work.

[Blackbird]

So, essentially a tankslapper is an uncontrollable dynamically amplified head shake, that, unlike a normal head shake, does not stabilise.

Thanks Shaun and Ixion, much clearer now. It sorted it out by itself thank goodness, I was preparing to get hurt so there was no intervention from me.

[Finn]

Do you have any contact details for the tapping to be done?

You lookin for a head shake?

[Shaun]

You lookin for a head shake?



I will take what I can get, but a full on slapping would be much more betterer

[Jimmy B]

Only my opinion!

I hate the linked break thing, I really believe that the rider should be in controll of there own destiny, but I also hate ABS systems, you cannot stop as quick with ABS as you can with a normall system

Thanks Shaun,

I quite like linked brakes but you skill level and mine would be worlds apart :yes:

I was more referring to your comments about applying the rear and pinning the throttle to sort out a TS. Linked brakes will fire a pot on the front when you apply the rear; do you think that your technique would still work despite this automatic application of a little front brake?

[N4CR]

i find on the two bikes i've ridden the most, slappers are very related to the tyre pressures (of course surface causes them though but the thign that lets them is the pressure). almost been spat off like lou's first post on the zxr250, same speeds same thing. had bike going between my thighs leg to leg like the iom clip everyone has seen and almost toppling off it... many many slappers on that thing and the 10r lately (pressures too high!!!)

[Shaun]

Thanks Shaun,

I quite like linked brakes but you skill level and mine would be worlds apart :yes:

I was more referring to your comments about applying the rear and pinning the throttle to sort out a TS. Linked brakes will fire a pot on the front when you apply the rear; do you think that your technique would still work despite this automatic application of a little front brake?



No mate, I do not think my technique will work in this situation

[Shaun]

i find on the two bikes i've ridden the most, slappers are very related to the tyre pressures (of course surface causes them though but the thign that lets them is the pressure). almost been spat off like lou's first post on the zxr250, same speeds same thing. had bike going between my thighs leg to leg like the iom clip everyone has seen and almost toppling off it... many many slappers on that thing and the 10r lately (pressures too high!!!)



You can also all but gaurantee that the stearing head bearings are to loose and not packed with grease properly, allowing the stearing axis to be loose and subject to a lot of movement by bump stearing on the road

[Disco Dan]

You can also all but gaurantee that the stearing head bearings are to loose and not packed with grease properly, allowing the stearing axis to be loose and subject to a lot of movement by bump stearing on the road

So would a shot steering head bearing be a high contributing factor to a tankslapper?

[Edbear]

So would a shot steering head bearing be a high contributing factor to a tankslapper?





Probably, since they're at the top...:yes:

[avgas]

3. Not all sportbikes need a steering damper, however. Many have steering geometry setups that offer quick handling, while still providing the necessary stability to damp out any front-end oscillations.

Fazer is awesome at this, i just about dropped her comming out of the classic races. Back tyre was full of gravel in the grip and i opened the throttle only to have the back kick out and drop the bike to a 20 degree angle before i killed the throttle and threw the bars back up again.
Didnt have time to get the stabiliser out, was so thankful that i didnt have clipons then.

[avgas]

You can also all but gaurantee that the stearing head bearings are to loose and not packed with grease properly, allowing the stearing axis to be loose and subject to a lot of movement by bump stearing on the road

Its funny you mention that cos i had the exact opposite happen when my bearing was failing on one of my previous bikes. It didn't like turning - like it had a dampener on it.

[Shaun]

So would a shot steering head bearing be a high contributing factor to a tankslapper?


Very well could be

[Shaun]

Its funny you mention that cos i had the exact opposite happen when my bearing was failing on one of my previous bikes. It didn't like turning - like it had a dampener on it.



Which could also cause slappers

[idleidolidyll]

damn the demon drink! hic!

came here looking for 'tanked slappers' only to find a bunch of motorcyclists talking bike stuff

my 'polagies

[idleidolidyll]

Only my opinion!

I hate the linked break thing, I really believe that the rider should be in controll of there own destiny, but I also hate ABS systems, you cannot stop as quick with ABS as you can with a normall system

agreed

anecdote:
owned a motorcycle courier business in Cardiff, Wales. One day my bus partner and I headed off to Caerphilly over the mountain for a spin and I watched Scelly pull into the big layby at the top where the obligatory burger cart lurked surrounded by customers and people looking at the view. Scelly was in front by a good margin and as he hit the gravel he hit the rear brake and slid into a nice controlled stop with the crowd in awe.

Thinking "shit, that was cool" I started to do the same thing only to remember too late that I was on a Guzzi with linked brakes.

I'm still not sure what was more painful: the gravel rash or the hysterical laughter from about 30 onlookers.

I hate ABS, it lacks feel and ultimate power and linked brakes don't do it for me as I use rear wheel braking a little to steer the KTM

[Morcs]

Ive had the vfr 2 days and ive already experienced 5 small tankslappers (3-4 turns of the wheel from side to side)

Its pretty much self induced though, when flat tack in first, changing to second aggresively it always seems to do it - is it more to do with the bike or me being agressive on the bars - clutch in hard, throttle off hard, clutch out hard and throttle on hard?

Its only scary when it actually happens on a bumpy piece of road, where the front wheel comes off the ground...

:mellow:

[Shaun]

Ive had the vfr 2 days and ive already experienced 5 small tankslappers (3-4 turns of the wheel from side to side)

Its pretty much self induced though, when flat tack in first, changing to second aggresively it always seems to do it - is it more to do with the bike or me being agressive on the bars - clutch in hard, throttle off hard, clutch out hard and throttle on hard?

Its only scary when it actually happens on a bumpy piece of road, where the front wheel comes off the ground...

:mellow:


By the sound of things, you are being to aggresive with handle bar controls input, try smoothing out your actions a little and see what happens

[TonyB]

Morcs- it could also be the forks. If the damping is shot, you'll get this problem a lot. On my FZR, this problem was frequent, when I was riding like a delinquent. So I had the forks repaired, and the problem disappeared.

[Toaster]

Had a wicked tank slapper last year on my previous bike -a GSXR. Lost traction on the rear just as I opened the throttle with wonton abandon, slapped that front around like heck and just managed to stay on.... slammed my foot down in the process and shattered one bone and split the other from top to bottom in my foot.

[terbang]

Must admit I prefer the 'tanked slappers' any day over the motorcycle kind. They're prettier.

[NordieBoy]

Its pretty much self induced though, when flat tack in first, changing to second aggresively it always seems to do it - is it more to do with the bike or me being agressive on the bars - clutch in hard, throttle off hard, clutch out hard and throttle on hard?

Less arm, more wrist.

:shutup:

[dank]

Both kinds of slapper are dangerous and expensive on the wallet.
Ive had many, the bike tends to do it sometimes also. wha whaaaah.

[Skyryder]

Na a tankslapper is a biker whose rodgered his ol' lady on the tank of his bike. It's why Harleys have two filler caps on each side. Give's the ol' girl somit to hang on to.

Skyryder

[ducatilover]

argh if only i read this in 2005......i was told to lean back during a tankslapper as to take the weight off the front wheel to reduce the harmonic imballance:angry:

[ducatilover]

this is waht my first real tankslapper did....:blink: it kinda hurt too

theres a huge wrist dent in the tank lol. and im sure a few things may have fallen off. :whistle:




argh pictures wont load:Oi:

[idleidolidyll]

Well it's all about a lack of control of course.

The speed bump on the road of life that sets a slapper up for ridicule and derision is usually alcohol and yes, they get well and truly tanked sometimes.

However, at some time in their life, most men will seek a tanked slapper for a bit of recreation.

It's a natural thing.

[classic zed]

The best way I have found to get out of a tank slapper (and Iv had a few over the years) is to lay down on the tank, it lowers the centre of gravity and stops it almost immediately :niceone:

[Roki_nz]

Not sure if you guys have seen it but go it from this site:

http://www.msgroup.org/tip.aspx?num=190


A tank-slapper (wild and rapid swings of the handlebars from hard-stop right to hard-stop left and back again) happens when harmonic feedback is generated following your front tire hitting an imperfection on the road surface such as the slight bump at the end of your driveway.

It usually happens at speeds of around 20 MPH - sometimes a little faster, sometimes a little slower - but it CAN happen at any speed!

I have heard otherwise well informed riders give advice to newbies about how to handle a tank-slapper. Usually it goes something like this: 'Just hit the throttle and lift the front-end off the ground. That will stop the oscillation."

Please! That advise is virtually assured of getting you into serious trouble - more than you were in when the tank-slapper began.

Harmonic feedback means that a small force is being applied EXACTLY in-phase with the end of a counter-force (shock absorber) which results in another 'bounce' of the system AND AN AMPLIFICATION of the previous bounce.

The second time it happens the amplification is huge. The third time and you eat asphalt - maybe the fourth time...

It is exactly the same principal that keeps your old grandfather's clock pendulum swinging - it gets a tiny 'kick' at exactly the right time (in-phase) at the end of each swing.)

Your bike probably has one of two kinds of devices in it designed to prevent these from happening:


A small shock absorber attached to the steering stem

A pressure bearing within the triple-tree
These are called steering head dampers or 'stabilizers'. Their sole legitimate purpose is to disrupt harmonic feedback and, thus, stop tank-slappers before they start. Some vendors (and motorcycle shops) will tell you to get one in order to stop your front-end from 'shaking'. NUTS! If your front-end shakes at any speed there is something wrong with the suspension.

If your steering head damper is weak or maladjusted then it cannot dampen (and, thus, kill harmonic feedback) shocks to the front-end.

As to suggestions about how to handle one if it happens ... it is NEVER appropriate or safe to do a wheelie. Your response should be to hold firmly to both grips and absorb the 'harmonic feedback' into your arms - i.e., dampen them - and grabbing a handful of the front brake. Then go get it fixed!

Your NUMBER ONE RESPONSIBILITY on a bike is to maintain control of it.

For those giving advice ... if your bike is already out of control do you really think it makes sense to increase speed? To do a wheelie? Does it not occur to you that you were traveling at some rate of speed and it was just a minor imperfection in the road surface that started this and that when you come back down from a wheelie, going faster than you were, that front-end is going to get a severe jolt? What do you think the odds are of going into another tank-slapper then?

You must disrupt the harmonic. You do that by stiffening your arms and changing the front-end geometry, if you can. Braking, by the way, both slows you down so that if you do hit the ground it won't hurt as much, and it compresses the front shocks which changes the front-end geometry.

Sound like a better alternative to you than hitting the after-burner?

[Ixion]

IMHO (and I survived a few on the Killersaki 500) the writer of that article has no idea what he is talking about. And his advice is dangerous.

They usually occur at far more than 20mph

Even if it were possible to "hold firmly to both grips and absorb the 'harmonic feedback' into your arms" (it's not, the bars will just be wrenched out of your hands no matter how strong you are), the only result would be to break your arms.

[jcupit69]

Some after market steering dampers are dangerous 2. Had one on my zxr and although it helped ALOT at going over bumpy spots at speed (anyone whos riden up the main road in churton park just after the school will no 1 bit im talking about), but when i crashed the steering damper almost went threw my leg due the angle at which it went on the bike and ended up leaving me a big scar just below my knee.
It also ment that in some corners youd find something tapping your leg, which wasnt much fun when trying to lean into a corner. Like i said they are great lil things, just make sure you check the position of them before you by one.
See pic and you'll see what i mean (excuse the dent in the gas tank)

[Ripperjon]

IMHO (and I survived a few on the Killersaki 500) the writer of that article has no idea what he is talking about. And his advice is dangerous.

They usually occur at far more than 20mph

Even if it were possible to "hold firmly to both grips and absorb the 'harmonic feedback' into your arms" (it's not, the bars will just be wrenched out of your hands no matter how strong you are), the only result would be to break your arms.

I totally agree with you there Ixion.

I had my first real tankslapper the other day.
I was going fairly fast and hit a series of lumps.
Before i knew it, the handlebars were going wild! It was pretty full-on and i thought i was gonna hit the deck, but it steadied out pretty quick. In reality, i'd say it only lasted a couple of seconds but in that time the bars would've done at least 10 flicks back and forth.
I've read your advice on tankslappers in the past Ixion and i think it definitely helped in that split-second when i decided not to fight it. I try never to ride with too firm a grip and when the bars started going doo-lally, i remembered what i'd read and stayed loose.
If i had held on tight, i am certain my whole body would've been wrenched side-to-side and i would've been extremely lucky not too have been sliding the rest of the way to work.
As it turned out, it came and went with nothing but a sore palm in it's wake.

Cheers Ixion

[munterk6]

I slap a tanker most nights...does that count? :bleh:

[Ripperjon]

Leave your mum outta this, eh? ;p

[motorbyclist]

that post is an absolute load of bollocks, relying on bullshit to justify it's pseudoscience. the original post back in 2006 was much better

first of all, they can happen at any speed

next, hitting the gas and thus removing weight from the front and stiffening the chassis is a very effective way of stopping tank slappers. while i'm sure in some rare cases the geometry of the bike, degree of slapping, and power of engine may conspire to make this worse i've always found it to be successful - and if you gas enough so the front wheel ain't on the ground it isn't going to "slap"

the absolute worst thing you can do is hitting the front brake

a good idea is to relax your grip on the bars - often it is you that is making the oscillations worse.


tankslappers usually arise where the front, for whatever reason, has come out of line with the rear wheel and the rear is still (more or less) in line with the momentum of the bike, ie, not drifting.
say the front has jumped left - the bike's momentum wants to keep going forward. the traction of the tyres will now exert forces to correct this, by leaning and steering slightly to the right, but of course if the wheel doesn't straighten fast enough it will overshoot, and now be on the right of the bike's trail as the bike starts to lean left as the wheel runs out from under it to the right. wheel comes back around and if you're unlucky it'll overshoot again. sometimes it'll do so in such a way it gets worse and worse and before you know it the rear wheel is getting flicked around too, you've been thrown off the bars, and there's a fast approaching tree. if you want to test this, go down the motorway and give the handlebar a good nudge on one side, you'll notice the bike oscillate a few times before getting straight again (i'm not accountable if you have an accident doing this obviously dangerous test)

holding on tighter will not help unless you are a human supercomputer capable of applying forces to cancel out the oscillations of the handlbars. you will usually only make it much worse much faster

front brake just puts more weight on the front, pushing it further past the neutral position (so it'll overshoot more) and make things worse.

loosening your grip will save you being thrown off the bike, and let it sort itself out

rear brake can help change bike geometry, and stiffen the chassis.

hit the gas instead and the bike stiffens, geometry changes (including an increase in rake angle, which is exactly what you wish you had right now; when was the last time a chopper got a tank slapper?) and the weight all comes off the front wheel, allowing it to get back in line

of course this also speeds you up, which is not good in a crash and as such is rather counterintuitive, thus we have the ramblings of the bollocks post

but, if you've ever ridden a dirt bike you'll already have this "if in trouble, pick up the front" instinct nailed ever since you first hit the brakes on coming across an unexpected gully/ditch/drop/woops/jump and got a face full of dirt


just make sure you check the position of them before you by one.
See pic and you'll see what i mean (excuse the dent in the gas tank)

dude! not only is that the only dampener i've ever seen in that position, but how could you not see that being a hazard while riding?!

[Ripperjon]

Which post is absolute bollocks?

[motorbyclist]

http://www.kiwibiker.co.nz/forums/showpost.php?p=1399899&postcount=90

the "hold on tighter, use front brake and don't dare use gas" one

[enigma51]

http://www.kiwibiker.co.nz/forums/showpost.php?p=1399899&postcount=90

the "hold on tighter, use front brake and don't dare use gas" one

Had a tank slapper the other day coming on the front straight of taupo and the only thing that made me keep it pinned was jimmy telling boomer not to let of the gas cause thats what the dunlop slicks do when you power it on.


I shat my pants all the way down the front straight ........ so if any wants some leathers send me a pm they need a wash

[motorbyclist]

if boomer would like to correct me, i'd be happy to hear his story

[Reckless]

I've had a few on the old bikes over the years. The Z1 had it at 120k without fail, for a while, got worse as you pushed it faster. Soon found that Cycletreds hadn't seated the front axle correctly after a new tyre.
The VTR 1000 used to get a bit of headshake gunning it hard out of a corner but that was quite fun, just a couple of small variations as the weight came back on the front. Always settled without me having to take evasive action, either that or I wasn't pushing it hard enough to upset it more. Wasn't tyre pressures either I'm real fussy with that. I can seem to tell for some strange reason if the tyres are even 2 PSI out. Dunno why, the bike just feels awful?? I suppose its the same for most of you guys as well. Although I have ridden with quite a few guys that don't seem to give a damn about their tyre pressures?
Anyway was going to tell about the last big one I had. Was about 12 months ago at the Trailblazer on the CR250. Softish tyre pressures for the pumice in the forest then you hit a hell for leather gravel road link. Blasting along in top gear on gravel, on a bike already geared high to take the nasty out of it in the tight stuff. Top gear nearly flat out so I was already going fast enough to have me thinking OH shit! I hit a series of pot holes that threw the front into a wild Slapper. To violent to control even with the wide bars of a MX bike. I just did what all MX'ers do, shat myself and stuck with the bike. When your that far up shit creek you either jump off or stick with it. I've always been to scared to bail out, cause that's definitely gonna hurt, and nearly every bike I've ridden has been better than me, so I always ride it out if I can! But its usually good luck rather than good management on my part! But it was a good long tank slapper!

[Chrislost]

Not sure if you guys have seen it but go it from this site:

http://www.msgroup.org/tip.aspx?num=190

You must disrupt the harmonic. You do that by stiffening your arms

Thus transfering the slapper to your bike and your ass to the ground...

keep it pinned and let it slap. it will stop.
steering. well any decent rider can steer with no hands.

[Tank]

Leave my slappers out of this.

[camchain]

This doesn't explain all tank slappers, but seems to me when bike is accellerating hard the fork spring rate is out of whack with suddenly light front end. Hit the right sharp bump(s) and energy can't be absorbed properly by the spring and energy has to go somewhere.

TL 1000S: After enthusiastic bike journalists parked first TLs in hedges/ditches, Suzuki's hasty retro fit steering damper didn't totally sort the issue. Read a UK bike mag tech article on attempts to cure TL1000s of it's stank slappers. They reckoned the 'door closer' rotary damper had a lot to do it. Testing employed some complicated physics, a set of bumps and a better damper.

I never had anything more than a bit of minor headshake on my TL until one fine day accellerating hard (in a straight line and at a bit over 100kph) hit the right combination of throttle and knotty bumps and whammo! Not quite lock to lock but scary enough. After having the frame break a few weeks earlier, this was the end of the affair with the wicked and beautiful TL.

Dirty bikes: Skank spankers were a lot more common on old short travel dirt bikes than they are nowadays. No more travel? time to hammer those steering locks says Mr Physics. E = mc buggered (where mc = motorcycle)

[nico]

any1 know if thers a stearing damper out there to fit vfr750f"s ??????? or would that not be a good idea

[dpex]

I think that guys who ride Harleys are genuine tank-slappers.

Today I stopped at the lights beside a Harley man.

'Great day, Huh?'

'The best.' And it was.

'Your bike good in corners?'

'Mate. Harley's don't corner unless you're really strong.'

He smiled. The lights turned green. I offered him first off and watched him round the corner like a dancer with a really big stake up her bum. Placed a slight extra weight on Yami's inside peg and down she went...Elegance compared to force.:scooter:

But geez. They sound good, huh?

[racefactory]

that post is an absolute load of bollocks, relying on bullshit to justify it's pseudoscience. the original post back in 2006 was much better

first of all, they can happen at any speed

next, hitting the gas and thus removing weight from the front and stiffening the chassis is a very effective way of stopping tank slappers. while i'm sure in some rare cases the geometry of the bike, degree of slapping, and power of engine may conspire to make this worse i've always found it to be successful - and if you gas enough so the front wheel ain't on the ground it isn't going to "slap"

the absolute worst thing you can do is hitting the front brake

a good idea is to relax your grip on the bars - often it is you that is making the oscillations worse.


tankslappers usually arise where the front, for whatever reason, has come out of line with the rear wheel and the rear is still (more or less) in line with the momentum of the bike, ie, not drifting.
say the front has jumped left - the bike's momentum wants to keep going forward. the traction of the tyres will now exert forces to correct this, by leaning and steering slightly to the right, but of course if the wheel doesn't straighten fast enough it will overshoot, and now be on the right of the bike's trail as the bike starts to lean left as the wheel runs out from under it to the right. wheel comes back around and if you're unlucky it'll overshoot again. sometimes it'll do so in such a way it gets worse and worse and before you know it the rear wheel is getting flicked around too, you've been thrown off the bars, and there's a fast approaching tree. if you want to test this, go down the motorway and give the handlebar a good nudge on one side, you'll notice the bike oscillate a few times before getting straight again (i'm not accountable if you have an accident doing this obviously dangerous test)

holding on tighter will not help unless you are a human supercomputer capable of applying forces to cancel out the oscillations of the handlbars. you will usually only make it much worse much faster

front brake just puts more weight on the front, pushing it further past the neutral position (so it'll overshoot more) and make things worse.

loosening your grip will save you being thrown off the bike, and let it sort itself out

rear brake can help change bike geometry, and stiffen the chassis.

hit the gas instead and the bike stiffens, geometry changes (including an increase in rake angle, which is exactly what you wish you had right now; when was the last time a chopper got a tank slapper?) and the weight all comes off the front wheel, allowing it to get back in line

of course this also speeds you up, which is not good in a crash and as such is rather counterintuitive, thus we have the ramblings of the bollocks post

but, if you've ever ridden a dirt bike you'll already have this "if in trouble, pick up the front" instinct nailed ever since you first hit the brakes on coming across an unexpected gully/ditch/drop/woops/jump and got a face full of dirt



dude! not only is that the only dampener i've ever seen in that position, but how could you not see that being a hazard while riding?!

This is good but you seem to have covered everything but body position. Can we just infer that as the main goal is to have the WEIGHT OFF OF THE FRONT, therefore we should be not leaning forward so much and instead be sitting more upright and back?

[motorbyclist]

This is good but you seem to have covered everything but body position. Can we just infer that as the main goal is to have the WEIGHT OFF OF THE FRONT, therefore we should be not leaning forward so much and instead be sitting more upright and back?

i just sit wherever is comfortable (nc30 will sort itself out), though i do notice i gradually move forwards on the seat as the tank empties out....

[The Lone Rider]

Dang, I didn't know there was already a term "tank slappers"

For the past year or so, I have been referring to a lot of motorcycle girls I have met through motorcycles, as tank slappers. Mainly due to them being of the "groupie" nature and passing themselves around - good time... not long time.

Not my thing, not into them tank slapper girls. To the curb they go when I find out their motivations!

[86GSXR]

I've had a couple of scary ones years ago on first generation Gixxers. But last Sunday I had the most close up encounter with one of these bitches to make me never want to encounter one again. Put me in hospital for two days and I'm now recovering from four broken ribs, a cracked shoulder blade, a badly broken hand, plus various scrapes and abrasions.

I was going up the Pahiatua track, one of my favourite roads and one I've done hundereds of times.

I was following a mate on a Sprint ST and I was on my (now wrecked) 08 Tiger.

All was normal, we were travelling at a reasonable, legal pace and just coming out of an uphill right hander onto a short straight. It was a beautiful sunny day, no wind and a completely dry road in good condition. In short, a perfect biking day.

My tyres (Pilot Roads) were warm and in decent condition. The front and rear suspension were set up pretty well for my weight and riding style.

As we rounded the bend my front suddenly let go and slid a few inches to the left. I have no idea why it slipped, maybe there was a small stone, diesel patch, slippery patch, whatever.

When it regained traction the bike started to highside me off to the left. I reacted pretty quickly and hoisted it back but by then the front and rear had become completely uncoordinated and I was in the midst of the most violent and powerful tankslapper I could ever have imagined.

I tried applying power and tried to even it out but I was helpless to do anything in a controlled manner as the oscillations were just too powerful.

The only thing I could do was to just bail off before I was thrown off. I did that and landed hard on my back on the right side doing the aforementioned damage to myself.

It's a bit of a blur after that, but apparantly my bike kept on shaking itself up the road before falling over and sliding up the road and down a bank.

Later on in hospital my friend told me that he'd seen most of it in his mirrors and I'd looked like a rag doll with my legs going everywhere. I don't remember that bit as I must have been too busy trying to control it, unsuccessfully.

I was saved by my fully armoured and well fitting leathers, which held up pretty well. My helmet was really crunched in at the front and I thank god I always wear my gear and had made a point of making sure my helmet strap was tight before setting off.

I'm in for a few weeks of pain yet though, broken bones, especially ribs are NOT fun!

Always wear armoured, snug fitting gear and do your helmet up securely PLEASE! I wouldn't wish this shit on anyone :done:

[BMWST?]

my Ductai S2 used headshake over railway lines etc ,only under accelleration ,hit the bump and the head would shake 1,2,3, and then be dead smooth again.

[Motoracer]

Crossed up wheelie landings can trigger em too.


http://www.bikepics.com/movies/000464/


Also trying to Manhandle a rolling stoppie at speeds of say over 50kmph once the stoppie has already comenced into full 'roll' (nearing balance point). Manhandle as in trying to correct or manuver the path of the stoppie.

Another major catalyst resulting in a slapper is ofcourse, fuked steering head bearings. If they are rooted, get em fixed ASAP. Otherwise, once you hit a few bumps at speed, it could be all over!

[erik]

...
As we rounded the bend my front suddenly let go and slid a few inches to the left. I have no idea why it slipped, maybe there was a small stone, diesel patch, slippery patch, whatever.

When it regained traction the bike started to highside me off to the left. I reacted pretty quickly and hoisted it back but by then the front and rear had become completely uncoordinated and I was in the midst of the most violent and powerful tankslapper I could ever have imagined.
...


Are you sure it was a tank slapper and not fish-tailing (rear end losing traction)?
The marks on the road look too wide to me to be from a tank slapper.

Anyway, get well soon.

[Chrislost]

The only thing I could do was to just bail off before I was thrown off.


Thats a stuff up! Heal well!

Ya can get slappers if the back lets go briefly and comes back...

I have seen those exact marks appearing in front of me from the BACK WHEEL of a zx10 after the guy stepped the ass out on a bump and let go of the gas...

[ducatilover]

You can get good slappers with a bros650 if you don't know how to ride very well....not the kind of slapper we all love though :Oops::angry:

[86GSXR]

Are you sure it was a tank slapper and not fish-tailing (rear end losing traction)?
The marks on the road look too wide to me to be from a tank slapper.

Anyway, get well soon.


Thats a stuff up! Heal well!

Ya can get slappers if the back lets go briefly and comes back...

I have seen those exact marks appearing in front of me from the BACK WHEEL of a zx10 after the guy stepped the ass out on a bump and let go of the gas...

Thanks. Good points guys. Maybe the back did let go, it happened so fast it's a bit hard to tell. It felt like the front, but maybe.........?

Yep, three months now and I'm still not quite right. A lot better than I was then though :yes:


You can get good slappers with a bros650 if you don't know how to ride very well....not the kind of slapper we all love though :Oops::angry:

Give me the other kind any day :whistle: :laugh:

[motorbyclist]

a few weeks ago i clipped a reflector ona right hander at 100kph - front slipped about 15cm before regaining traction at which point the rear lost traction.

spent the rest of the corner with a meeaaan fishtail but just kept riding and it sorted itself out. gotta love the NC30/NC35 chassis :innocent:

[LaytonNZ]

This Happend to me wile going down a hill i hit some tree roots i was overtakeing doing 140 kmh sceard the shit out of me:P

[6ft5]

I was saved by my fully armoured and well fitting leathers, which held up pretty well. My helmet was really crunched in at the front and I thank god I always wear my gear and had made a point of making sure my helmet strap was tight before setting off.

I'm in for a few weeks of pain yet though, broken bones, especially ribs are NOT fun!

Always wear armoured, snug fitting gear and do your helmet up securely PLEASE! I wouldn't wish this shit on anyone :done:

Good luck with your recovery mate. Have had some bad time myself and after 12 months am finally coming right. :doctor:

[ready4whatever]

sounds scary. gotta hate the wobbles too

[jubilant]

riff raff , cheers for this post and to the admins for it being a sticky, it came in use today as i had a moment on the way home from work, just been cut up by a boy racer in his mums car so to avoid him i pulled into the other lane and hit a man hole cover...tank slapper time ( on my hyo 250 gt ) made me crap for a sec but i relaxed my grip and leaning forward sorted me out....shit my knickers though .....im just sitting down with a nice cup of tea to calm my nerves !!

thanks for this , if i hadnt have read it a few nights ago i wouldnt have had a clue and most likely have been on my way to northshore hospital to die of swine flu or mrsa or just through old age in the waiting room....

[batboy]

Right wondering if anyone has ideas on this...... weighted barends?

Now i have a set of these on the monster and one thing they do well is remove some vibration from the bars, but on the topic of tankslappers, do you think they will accentuate any slap that may occur.
My thought is that adding weight furthest away from the steering head would increase the oscillations in the event of said slap? does this make sense?

/discuss

[motorbyclist]

Right wondering if anyone has ideas on this...... weighted barends?

Now i have a set of these on the monster and one thing they do well is remove some vibration from the bars, but on the topic of tankslappers, do you think they will accentuate any slap that may occur.
My thought is that adding weight furthest away from the steering head would increase the oscillations in the event of said slap? does this make sense?



ok, i'm not in the mood to run the numbers, but it would make it slap slower, and possibly get into a slapper easier.

might be more complex than this, but generally, the bigger the mass the slower the resonant frequency

however, it would make the bars less prone to deflection, but only slightly.

[Geemsee]

Right wondering if anyone has ideas on this...... weighted barends?

Now i have a set of these on the monster and one thing they do well is remove some vibration from the bars, but on the topic of tankslappers, do you think they will accentuate any slap that may occur.
My thought is that adding weight furthest away from the steering head would increase the oscillations in the event of said slap? does this make sense?

/discuss

A bit late in the day, but i thought bar end weights were for damping handlebar vibrations not really for tankslappers?! Best fix is a steering damper kit but that might just be disguising the root of the problem ie I had a Z650 way back when it had Dunlop Endurance tyres on it when I bought it and boy did it used to tankslap, fixed it by putting some decent tyres on it, no damper required!! :headbang:

[Corse1]

Well luckily managed to survive a massive slapper around the East Coast between Te kaha and Waihau Bay on Wednesday. Leaned over powering out of corner and hit bump. Away she went with both tires chirping almost at the same time side to side about 8 times.....sounds like I did the right thing as I did not bin it only reading this sticky tonight.
I thought I was a gonner though for sure. Radical Speed triple geometry combined with harsh standard rear shock. I have some investing to do as I sure do not want that to happen again!! :eek5:

[pritch]

I have never felt the need for a steering damper. Until just lately - the thought having recently occurred on a number of occasions. I note that Ohlins list one for the model, and that at least one road test recomends it. Now if only I could figure out how to pay for it...

[rok-the-boat]

I agree with the premise of the original posting, but, it is not only the surface of the road - it can also be the design of the bike. My mate's Suzuki GT750 would tankslap between 80-90mph. It would start with a steady weave and then turn violent. You could ride thru it and come out the other side 90mph+ or, slow down - the usual instinct. If you accelerated fast you would go thru 80-90 so fast you wouldn't notice it, but you knew you have to go back down thru it - very disconcerting, as I remember. It did this on any road, any surface etc, bumpy or smooth.

[FlyingKiwi]

Well, this all makes for some scary reading! Fingers crossed for me I guess

[Metastable]

With a true sudden lock to lock tank slapper there is NOTHING you can do. Like some guys have said, you're on for the ride. I was going over a set of double railway tracks and BAM!... the bars went lock to lock 3 times and the first one ripped my hands straight off the clip ons, which is probably a good thing... she went into a strong weave and then settled down. It happened so fast that I really couldn't do squat.

Suspension set up is HUGE! It can make things a lot less likely to happen and of course a steering damper is a good idea too..... although maybe I'm just stupid, because don't have one on my trackbike yet. :D

[bkker]

man, sounds bad. glad I haven't had to experience this yet, not looking forward to it. I've been on a few really bumpy corners, but luckily no slapping :P

[Chrislost]

riff raff , cheers for this post and to the admins for it being a sticky, it came in use today as i had a moment on the way home from work, just been cut up by a boy racer in his mums car so to avoid him i pulled into the other lane and hit a man hole cover...tank slapper time ( on my hyo 250 gt ) made me crap for a sec but i relaxed my grip and leaning forward sorted me out....shit my knickers though .....im just sitting down with a nice cup of tea to calm my nerves !!

thanks for this , if i hadnt have read it a few nights ago i wouldnt have had a clue and most likely have been on my way to northshore hospital to die of swine flu or mrsa or just through old age in the waiting room....


One twitch upon hitting a man hole in the wet, doesn't even smell like a tank slapper.
may make ya heart beat a tad faster if your not expecting it tho...

[thepom]

I had a real bad one on the gravel and woodsman was following me,I was doing 100 k,s and it spat me off after a hundred meter slapper,bike landed on my ankle after I face planted myself..........woodsman said it was hilarious...

[Woodman]

I had a real bad one on the gravel and woodsman was following me,I was doing 100 k,s and it spat me off after a hundred meter slapper,bike landed on my ankle after I face planted myself..........woodsman said it was hilarious...

Hilarious and scary at the same time. :shit::shit::yes:

[R-Soul]

Not sure if you guys have seen it but go it from this site:

http://www.msgroup.org/tip.aspx?num=190


A tank-slapper (wild and rapid swings of the handlebars from hard-stop right to hard-stop left and back again) happens when harmonic feedback is generated following your front tire hitting an imperfection on the road surface such as the slight bump at the end of your driveway.

It usually happens at speeds of around 20 MPH - sometimes a little faster, sometimes a little slower - but it CAN happen at any speed!

I have heard otherwise well informed riders give advice to newbies about how to handle a tank-slapper. Usually it goes something like this: 'Just hit the throttle and lift the front-end off the ground. That will stop the oscillation."

Please! That advise is virtually assured of getting you into serious trouble - more than you were in when the tank-slapper began.

Harmonic feedback means that a small force is being applied EXACTLY in-phase with the end of a counter-force (shock absorber) which results in another 'bounce' of the system AND AN AMPLIFICATION of the previous bounce.

The second time it happens the amplification is huge. The third time and you eat asphalt - maybe the fourth time...

It is exactly the same principal that keeps your old grandfather's clock pendulum swinging - it gets a tiny 'kick' at exactly the right time (in-phase) at the end of each swing.)

Your bike probably has one of two kinds of devices in it designed to prevent these from happening:


A small shock absorber attached to the steering stem

A pressure bearing within the triple-tree
These are called steering head dampers or 'stabilizers'. Their sole legitimate purpose is to disrupt harmonic feedback and, thus, stop tank-slappers before they start. Some vendors (and motorcycle shops) will tell you to get one in order to stop your front-end from 'shaking'. NUTS! If your front-end shakes at any speed there is something wrong with the suspension.

If your steering head damper is weak or maladjusted then it cannot dampen (and, thus, kill harmonic feedback) shocks to the front-end.

As to suggestions about how to handle one if it happens ... it is NEVER appropriate or safe to do a wheelie. Your response should be to hold firmly to both grips and absorb the 'harmonic feedback' into your arms - i.e., dampen them - and grabbing a handful of the front brake. Then go get it fixed!

Your NUMBER ONE RESPONSIBILITY on a bike is to maintain control of it.

For those giving advice ... if your bike is already out of control do you really think it makes sense to increase speed? To do a wheelie? Does it not occur to you that you were traveling at some rate of speed and it was just a minor imperfection in the road surface that started this and that when you come back down from a wheelie, going faster than you were, that front-end is going to get a severe jolt? What do you think the odds are of going into another tank-slapper then?

You must disrupt the harmonic. You do that by stiffening your arms and changing the front-end geometry, if you can. Braking, by the way, both slows you down so that if you do hit the ground it won't hurt as much, and it compresses the front shocks which changes the front-end geometry.

Sound like a better alternative to you than hitting the after-burner?

I agree with Ixion - this sounds like the exact opposite of what you should do. I agree with the definition of what a tankslapper is, but not their proposed rsponse.

First they explain that it is teh small "kick" that gets given to the pendulum in a granfather clock that keeps it swinging in harmonic fashion, and then they say that you should stiffen your arms? Stiffening your arms will GIVE the handlebars that additional kick that counters the DAMPING action of the forks.

I had an experience with a car that is quite a good analogy to this:
A rabbit jumped out onto the highway while I was glancing down. As I looked up, I saw it and jerked the steering wheel by reflex. the car swerved to the side, and I corrected, which made it swerve to the other side more violently, which I corrected again, to make it swerve ebven more violently back again, etc etc until the back stepped out and the car did a 360 on the motorway (luckily at night, so it was empty). I was told by an advanced driver afterwards that the car suspension is designed to self correct to a straight line, and it was my arm inputs on the steering wheel that were causing the over correction. Taking that analogy to the bike - similarly by trying to hold the bars firmly, you are not letting the forks 'self damp'. Holding the bars loosely may be a better option.

From an engineers perspective, you can interfere with the harmonics caused by a regular periodic force (the force of the road on tyre) being applied at a resonant frequency to cause resonance by:
1) removing or reducing the forces being applied (by lightening the front wheel to reduce the force being applied by the road to the tyre and letting natural fork damping do the rest- like Shaun said)
2) damping the actual movement (like with a steering damper)

I cant think of any more although the comment earlier about a bike going sweetly into a turn was interesting. Perhaps applying force to only one side of the bars will interfere destructively with the periodic forces of the road on the tyre? In this case, then perhaps swerving from one side of the road to the other might help? Can somebody try this and let us know if this works?

:bleh: :msn-wink:

I can't think why back brake would help (except to slow the bike for it you do get thrown)? Perhaps by braking you are changing the frequency that the force of the road is acting on the tyre. If this is true, then I guess this would apply to both brakes then, except that with using the front brakes, the moving bars can cause damage to your arms. Also, if Shaun was accelerating while braking with the back brakes, then this would negate that effect. Any ideas?



In order to break a harmonic, you dont add force into teh equation at the

[SMOKEU]

I've had a few scary experiences when the Gixxer gets into a mild tankslapper, the worst was accelerating hard down a straight piece of road in 2nd gear and the front end started wobbling quite bad. Wasn't expecting that, especially considering the road was pretty smooth.

[Nzpure]

had what could only be explained as a tank slapper experince under severe heavy braking on the busa scariest moment of my life!

[ducatilover]

I've had a few scary experiences when the Gixxer gets into a mild tankslapper, the worst was accelerating hard down a straight piece of road in 2nd gear and the front end started wobbling quite bad. Wasn't expecting that, especially considering the road was pretty smooth.

More rear bound damping or more front rebound would sort it?
In my head...or maybe your tyre pressures were out/you should put more weight on the front.

Or keep it on one wheel bro

[ducatilover]

had what could only be explained as a tank slapper experince under severe heavy braking on the busa scariest moment of my life!

I've had me a few, best way I found to avoid 'em is not to ride hard. :laugh:

[R-Soul]

I agree with Ixion - this sounds like the exact opposite of what you should do. I agree with the definition of what a tankslapper is, but not their proposed rsponse.

First they explain that it is teh small "kick" that gets given to the pendulum in a granfather clock that keeps it swinging in harmonic fashion, and then they say that you should stiffen your arms? Stiffening your arms will GIVE the handlebars that additional kick that counters the DAMPING action of the forks.

I had an experience with a car that is quite a good analogy to this:
A rabbit jumped out onto the highway while I was glancing down. As I looked up, I saw it and jerked the steering wheel by reflex. the car swerved to the side, and I corrected, which made it swerve to the other side more violently, which I corrected again, to make it swerve ebven more violently back again, etc etc until the back stepped out and the car did a 360 on the motorway (luckily at night, so it was empty). I was told by an advanced driver afterwards that the car suspension is designed to self correct to a straight line, and it was my arm inputs on the steering wheel that were causing the over correction. Taking that analogy to the bike - similarly by trying to hold the bars firmly, you are not letting the forks 'self damp'. Holding the bars loosely may be a better option.

From an engineers perspective, you can interfere with the harmonics caused by a regular periodic force (the force of the road on tyre) being applied at a resonant frequency to cause resonance by:
1) removing or reducing the forces being applied (by lightening the front wheel to reduce the force being applied by the road to the tyre and letting natural fork damping do the rest- like Shaun said)
2) damping the actual movement (like with a steering damper)

I cant think of any more although the comment earlier about a bike going sweetly into a turn was interesting. Perhaps applying force to only one side of the bars will interfere destructively with the periodic forces of the road on the tyre? In this case, then perhaps swerving from one side of the road to the other might help? Can somebody try this and let us know if this works?

:bleh: :msn-wink:

I can't think why back brake would help (except to slow the bike for it you do get thrown)? Perhaps by braking you are changing the frequency that the force of the road is acting on the tyre. If this is true, then I guess this would apply to both brakes then, except that with using the front brakes, the moving bars can cause damage to your arms. Also, if Shaun was accelerating while braking with the back brakes, then this would negate that effect. Any ideas?


*IDEA* By braking, you are loading up the front end, and making the suspension stiffer, thereby causing more damping. that may be why it helps.

I hit a block of wood in teh road the other day, the bike flew up into teh air and the front wheel landed skew, making the head shake similar to a tankslapper. I loosened my arms, and let them flap with the bars, instead of fighting the bars. It shook itself out rather quickly, and damped itself of its own accord, and I was able to stay in control (but my rims were muntered).

Remember seeing how many riders come off the bike in races, and the bike carries on riding down the road, perfectly balanced, after the rider is chucked off? This is because it is deisgned to stay upright and damp itself.

[ShAdOwDrAgOnS]

Not many bikes seem to have a rep for doing it nowadays. ZX10R without damper and CBR600RR are the only ones I've heard about that will if provoked.

I haven't experienced a tank slapper yet. At most a slight tail wiggle when coming out of an uneven corner while accelerating hard and slightly losing traction and a few times where the front lifts up completely and you end up completing the corner on the rear wheel only until you can set the front down gently.

So far I’ve found the CBR 600RR to be a very forgiving bike.

Anyone else had tank slappers on a CBR 600RR?

[eldog]

tankslappers explained ok

There seems to be lots of ways to get one, all basically from the same problem, front wheel, bike travel direction misalignment

In my case, I was a beginner, had only ridden the bike maybe 100ks, as going slow 70 in the wet.
Yes the bike did have bar end weights.
It had PR3 tyres which were nicely scrubbed in.
I had the bike going through a slight corner/bend in the road, It was vertical as I travelled 1/2way through the corner, hit big patch of wet tar bleed, rear slid out along way, I twisted on the bars (like in a car-silly me) and it was on, never thought my arms could move so fast.

Since I was a beginner when I had mine and I hadnt read this thread. Since reading it, i am still a little confused
Instinctively I tried the stiff arm solution, seemed to get worse, I did think this would be similar to the steering damper idea.(At least that's what wet through my mind at the time). Seeing this didn't help, while I kept the throttle as constant as I could, I relaxed my arms, the bike did seem to be settling, the frequency was decreasing. Until the rear regained grip - I am guessing then a high side, just completely threw me, I wasn't expecting the highside.

From the posts in the thread I am a little confused about how to attack this type of situation.
I my mind loosening my arms seemed to be working any one else agree/disagree?

NO I am not overthinking this or overanalysing it either, just interested in others thought more experienced than me

[Katman]

Since reading it, i am still a little confused


No kidding.

[eldog]

No kidding?

Enlighten a simple soul, who seeks wisdom from others.

Are you referring to the thread or to my post or both - now I am confused

[haydes55]

So you had a tank slapper, at the same time your rear wheel was sliding? Tbh that sounds like a fucking difficult situation to correct. In a tank slapper it's hard to moderate the throttle. But ideally you would want relaxed arms, lean back (although that might depend on what riding position your bike is) and slightly accelerate. Lifting your elbows allows you better control of the throttle, as does holding the throttle like a screw driver. But again, it's sometimes impossible to adjust your grip in a slapper.

High siding is caused by your bike pointing a direction that is different to your current direction of momentum (I.e. Where you would be going if it wasn't for the slide), when the bike regains grip. Ideally you will maintain the broken traction until your bike is pointing in your direction of travel. This is very difficult. Don't shut off the throttle (unless your rear end stepped out whilst breaking with no throttle, don't suddenly apply throttle). Get your weight into the inside of the bike, relax the steering (front wheel should stay pointing in the right direction if you relax your arms). You could take your outside foot off the footpeg to drop your body further into the inside of the bike (but that's debatable, just what I learnt from speedway when a highside was brewing, I've only had 2 or 3 rear wheel slides and haven't been thrown off yet, and all those times I lifted my outside leg off the peg and squatted onto my inside leg).

You can see the cure for both is fairly similar, keep the load as even as smooth as possible and relax the arms.

The best cure is prevention, maybe look at what lines you take into and through corners, how you apply throttle through the corner and how you read the road and identify hazards.

Again, just to reiterate, this is just what I have learnt from speedway and road riding. This info is what I do in these situations, I have thought about it and analyzed it in my head, so when it occurs I react instantly. I am not in anyway a riding instructor or 65 year old guru.

[DamianW]

In addition to keeping the throttle open and moving your weight forward I'm told that lifting your bum off the seat also helps.

[eldog]

In addition to keeping the throttle open and moving your weight forward I'm told that lifting your bum off the seat also helps.

I know I was already in this position - of the seat leaning in with head and body, keeping the bike vertical as I went into the corner speed 70 (corner is an easy 90k most of the time)when the rear slid out, this most likely reduced the amount of weight on the rear, when I hit the tar bleed (couldn't see it in the wet and dark, but he weight forward may have helped stop the front from sliding). The tankslapper happened after I wrenched the bars back. As the tanskslapper was reducing- almost ended- suddenly the rear got traction - highside - getting a big boost, then looking down and seeing the bike about 1+ metre beneath me, just going about is business driving along, not a care in the world. The air time I got was great. Oh yeah! I thought, this is what those motocross riders do - now where are the handlebars :laugh:

[BlackSheepLogic]

I think this would shift weight onto the front which is not what you want to do in this situation.


In addition to keeping the throttle open and moving your weight forward I'm told that lifting your bum off the seat also helps.

[DamianW]

I think this would shift weight onto the front which is not what you want to do in this situation.

I've read in a few places that moving your weight forward and onto the pegs will lower the bikes cog and reduce whip effects of the rear regaining traction. I saw this in last seasons BSB series when I think it was Chris Walker was coming around the final bend at Brands and for all money was high sided. He got his arse off the seat and body forward and saved himself. Under slo-mo replay it was extraordinary to see just how quick his reflexes were working. The feel those guys have for their bikes is beyond mere mortal me.

[James Deuce]

The only way to fix a tank slapper is to get the front wheel OFF the ground. Most people who say they saved a tank slapper, including top level racers, are bullshitting. It was luck.

[eldog]

I had the combo, rear slide, tank slapper, highside.
Its something I have learnt from. Just didn't expect them one straight after the other. It as like OMG what next. Ah yes, I am lying on a 100k road and a car is coming fast. Get up and off the road you idiot.

I was lucky I could ride the bike home. Even though I couldn't move my right arm at all, just twist the throttle and apply the brake was all that side could do. Used left arm to lift the right hand into place. Ten feet tall and bullet proof I was. Till I got home....

Worse was telling those who love me that I had had an accident. That was way worse.


Reducing the weight on the front seems like a good idea to minimise the bounce.

[DamianW]

The only way to fix a tank slapper is to get the front wheel OFF the ground. Most people who say they saved a tank slapper, including top level racers, are bullshitting. It was luck.

Keith Code's Twist of the Wrist 2,
Page 52

'Tankslapper Damper

Picking your weight up off the seat if the bike wobbles violently or slides and catches also works to reduce the effect of your body mass being so high on the bike. This allows the bike to correct and stabilize itself much easier. The less of a "whipping back and forth" mass you become, the quicker the bike will stabilize'

[eldog]

Keith Code's Twist of the Wrist 2,
Page 52

'Tankslapper Damper

Picking your weight up off the seat if the bike wobbles violently or slides and catches also works to reduce the effect of your body mass being so high on the bike. This allows the bike to correct and stabilize itself much easier. The less of a "whipping back and forth" mass you become, the quicker the bike will stabilize'

+1 I found this with the Scorpio, I try to constantly put about 10-20% of my weight on my legs when riding, makers the bike so much easier to control, more stable etc. Its a light bike. My legs are so much better for it.

[Banditbandit]

The only way to fix a tank slapper is to get the front wheel OFF the ground. Most people who say they saved a tank slapper, including top level racers, are bullshitting. It was luck.

Yeah mate .. when you're in a sweeper at 110klicks and the bars suddenly go full lock left to full lock right .. there's not much time to react .. you just know it's going to hurt ... and it did !!! (But I walked away ...)

[YellowDog]

Apologies if this has already been posted:

<iframe width="720" height="485" src="https://www.youtube.com/embed/z3OQTU-kE2s" frameborder="0" allowfullscreen></iframe>

[Saarg]

Wow! .... that's crazy. I only got about 10 min in ... But how bike tech has changed


Sent from my iPhone using Tapatalk

[eldog]

Apologies if this has already been posted:

If only my tankslapper was a simple as this:innocent::corn:

Banditbandit, mine seemed to go on for ever, I actually thought I had it under control as it became much slower and more stable-so much relief - relaxed on the bars (not sure about the throttle, I was trying to keep it steady)

but it may have all started with a weight transfer on a corner with almost no traction-cold wet tar bleed.
Over it now, I know what to look for on the road and what I think is what to do.

there is lots of video on google on tankslapping.

this thread reminds me that I should reread it again.

[Voltaire]

I've owned and still have a couple of the bikes in the video.
Only time I have experienced anything like in the video was riding from Split to Dubrovnik in 1989 on my freshly restored BMW R75/5. Two up with panniers and....a top box mounted behind the rear axle and it went into a severe wobble. I found the tyre pressures were too low.

I can't say that I have ever noticed it on the R90s or the Norton Commando.

My Racebike BMW R90 is good for 200+ over the hill at Hampton Downs and the only time it shook its head was the slight bump coming up the hill.
I've since replaced the old steering damper and its barely noticeable now.
It also runs ohlins on the rear and RT tweeked front end plus race tyres.
At over 90KG's I think I know why :laugh:
Back in the day I didn't know anywhere near as much about suspension/tyres/riding methods as I do now.

[Gonzo TR1]

Cruising back from the Brass Monkey south of Palmerston, noticed a glassy patch on the road, running straight and smooth at 90k, then all hell broke loose. The revs built up (wheel spin) and the BMW R80 took of sideways big time. Back of power to a violent tank slapper.Side to side for about 8 slaps and slowly came straight. Holly heck, if this is the joys of motor cycling you can stuff it. Totally unprevoked probible cause a patch of diesel,The weather was misty, damp, no rain, cold. My first big one. Riding for 50 years. Is it tme to sell my bike? :eek5:
Sounds like black-ice. Car or bike, just hang-on. I hit some on the desert-road a few weeks back, picking up my 'old-man-bike' (k75), just a little patch luckily. It still all went sideways, including trailer