Tankslappers explained

[MVnut]

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

[Roj]

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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

[Roj]

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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

[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]

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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]

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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:Me]

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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

[Finn]

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

[Blackbird]

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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

[Shaun]

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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

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]

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

No mate, just the good old arms

[Shaun]

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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.