Tankslappers explained

[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?

[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/sh...9&postcount=90

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

[enigma51]

http://www.kiwibiker.co.nz/forums/sh...9&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