View Full Version : What causes a........
Can someone explain what causes a tank slapper? Ive had quite a major one before with a pillion on board and although I learnt from that particular incident, generally im not entirely sure what causes it?
Head bearings, unstable geometry, landing a crossed up wheelie, hitting a manhole cover on the apex. Shutting off the throttle mid bend can do it too.
Some bikes are very prone to this, my 1985 GSXR750 did it frequently.
Flamin_Squirrel
30-01-05, 07:20 PM
A pilion will make you more susceptable also. With the centre of gravity further back, it'll be easier to lift the front under acceleration. With little weight on the front wheel, a bump in the road can get the bars to slap.
Loose head barings as burner said can contribute to this problem - I know Jonboy had problems because of this.
northwind
30-01-05, 07:43 PM
Badly setup rear suspension too.
If you go right back to basics, the front end of a bike is just like a castor on a supermarket trolley :shock:
Whether it's stable or not depends on stiffnesses of the tyre, forks, and frame, castor angle, mass (inertia) of the forks+wheel relative to the frame+rider etc, and to some extent any damping (such as a steering damper or tight/loose head bearings).
You'll know that supermarket trolleys are OK up to a certain speed and then go resonant, and it's the same with a bike. Most "resonant" systems can be forced through the critical frequency (speed in bike terms), but getting it through can be hazardous!
Carrying a pillion tends to make it worse because it tends to make the front end lighter relative to the rest. It usually helps if you both lean forwards to get more weight on the front.
Make absolutely sure the tyre pressures are right.
I've never had one. How do you control them?
chris SVK3
30-01-05, 08:36 PM
From what I have been told you need to keep a constant throttle and stay relaxed. Easy said than done. I have only had a tank slapper happen once on my old FZ400 and it scared the life out of me. Luckly the bike corrected it self and I stayed rubber side down.
bit of a noob, but whats a tank slapper anyway? the fuel in the tank going slapping against the sides or somthing?
Iain
carelesschucca
30-01-05, 09:22 PM
I've never had one. How do you control them?
You don't ever seen the Video of the guy at the TT on the Black Fireblade scary stuff...
http://www.StupidVideos.com/?VideoID=390
Fingers crossed this works and this is worst case Tank slapper, as far as I know the rider was ok (relatively speaking)
Flamin_Squirrel
30-01-05, 09:23 PM
Tank slappers are when the handle bars rapidly swing from side so side. They can range from a slight shudder to an extremely violent lock to lock motion. I assume they're called tank slappers from back in the day when there was nothing to stop the handle bars slapping into the tank :shock:
You don't ever seen the Video of the guy at the TT on the Black Fireblade scary stuff...
http://www.StupidVideos.com/?VideoID=390
Fingers crossed this works and this is worst case Tank slapper, as far as I know the rider was ok (relatively speaking)
that video always gets me. The guy so nearly recovers it.
Mythkind
30-01-05, 11:17 PM
You don't ever seen the Video of the guy at the TT on the Black Fireblade scary stuff...
http://www.StupidVideos.com/?VideoID=390
Fingers crossed this works and this is worst case Tank slapper, as far as I know the rider was ok (relatively speaking)
that video always gets me. The guy so nearly recovers it.
Ahh, that reminds me so much of my scariest moment though I managed to recover it (still not sure how). I decided I was a goner, especially as there was a car right up my ass that would have definately run over me had I come off. :shock:
MK
I had one once that was started by a rather bumpy surface on an 80 mph bend....I nearly browned meself but just held on :shock:
carelesschucca
30-01-05, 11:56 PM
Video made me sick the first time I saw it!!!
Captain Nemo
31-01-05, 12:46 PM
You don't ever seen the Video of the guy at the TT on the Black Fireblade scary stuff...
http://www.StupidVideos.com/?VideoID=390
Fingers crossed this works and this is worst case Tank slapper, as far as I know the rider was ok (relatively speaking)
that video always gets me. The guy so nearly recovers it.
when????
BaggaZee
31-01-05, 01:12 PM
as far as I know the rider was ok (relatively speaking)
As far as I remember he lost a few fingers at least! :shock:
It still scares me just watching it.
chazzyb
31-01-05, 01:38 PM
I had one once that was started by a rather bumpy surface on an 80 mph bend....I nearly browned meself but just held on :shock:
What, by clenching hard? Or are you talking about the bike?
:P
I would have to say the tank slapper I had was a major one, it really freaks you out when control is taken away from you like that. When I had my one I just thought of all the crash videos id seen and I knew what the end result was, I was convinced I was going to crash.
But I had been told before it happened to keep the throttle on enough to keep you moving, basically not accelerating and no engine braking at the same time and the bike did come back.
Friend said he will never get on a bike again, he needed alot of convincing anyway :lol: oops!
BaggaZee
31-01-05, 01:44 PM
I would have to say the tank slapper I had was a major one, it really freaks you out when control is taken away from you like that. When I had my one I just thought of all the crash videos id seen and I knew what the end result was, I was convinced I was going to crash.
But I had been told before it happened to keep the throttle on enough to keep you moving, basically not accelerating and no engine braking at the same time and the bike did come back.
Friend said he will never get on a bike again, he needed alot of convincing anyway :lol: oops!
How on earth do you keep the throttle constant when the bars are going lock to lock & yanking your throttle hand with them? :shock:
northwind
31-01-05, 02:54 PM
Good question! I used to get progressing wobbles under power that were obviously going somewhere bad but were slow enough that I could stop them before they got there, and every single time I had the image of that TT rider's bike just flying apart when it hits the ground...
I think it's a bit like powerslides or riding across bad gravel, just do as little as possible...
How on earth do you keep the throttle constant when the bars are going lock to lock & yanking your throttle hand with them?
Well thats what I have been told, I suppose complete accuracy is near impossible but when it happened thats what I tried to do as well as I could do and the bike corrected itself. Maybe there is another way?? Thats why I asked the question.
Some people say pop the front wheel up, SV wont do that very easily at 70mph.
northwind
31-01-05, 03:51 PM
Pull a wheelie? That's insane!
BaggaZee
31-01-05, 04:29 PM
Pull a wheelie? That's insane!
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :twisted:
I had one once on my YZF. It started small, but the more I tried forcibly to straighten the bars, the worse it got. In the end it was swapping sides that bad that I just couldn't hold the bars any longer. I let go and the bike sorted itself out. Grabbed the bars again and carried on.
It also happened whilst I was pillion and my friend went over a rail crossing on the back wheel. The bumps over the crossing made the bike drift across the other side of the road. There was only just enough time to get the front wheel down and swerve back to the right side of the road. This is when the slapper started. He also couldn't control it and took his hands from the bars. I was already looking for a soft place to land when it settled back down again. He grabbed the bars and we carried on.
Maybe there is an answer in there somewhere :?: :?:
So the combined knowledge of maybe 20 bikers is...
a.) pull a wheelie
b.) let go of the handlebars
:lol:
thanks lads, I feel much safer now.
carelesschucca
01-02-05, 12:03 AM
So the combined knowledge of maybe 20 bikers is...
a.) pull a wheelie
b.) let go of the handlebars
:lol:
thanks lads, I feel much safer now.
gonnie send us a video when you do it!!! I always like a good laugh!!!
kern0079
01-02-05, 12:25 AM
Here is a link to a 100mph wheelie turned tank slapper.
http://highspeedassault.com/images/HSA_Beanfield.wmv
Back in my younger days (15 years old) I had a 1958 Harley Davidson Sportster H. They had a steering damper knob to adjust handlebar movement stiffness. After cleaning the bike I decided to loosen that damper knob for a easier steering motion. Took it out for a test run to see how it effected the steering. I closed off the throttle at 70 mph and immediately went into a tank slapper. I got back on the throttle and the slapping movement eased. The moment I closed the throttle again back came the tank slapping. So I slightly eased back on the throttle with very, very light rear brake pressure. Once I had slowed to a 30 or 35 mph all was well again. It didn't take me long to tighten that steering damper knob back up.
Once you experience this phenomenon, you will never ever forget it. Cheers, Richard
Balky001
01-02-05, 12:46 PM
So the combined knowledge of maybe 20 bikers is...
a.) pull a wheelie
b.) let go of the handlebars
:lol:
thanks lads, I feel much safer now.
:lol: :lol: :lol: Is that either a) or b) or should you do both together? Wont you fall off the back? :wink:
I'm with Lee, relax and try not to force anything.
Had a couple of minor ones on my bandit when the suspension oil was shot it would just start to weave at about 90 and get worse. Generally getting on the power a little bit then easing off again helped... but not nearly as much as new fork oil!
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