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View Full Version : Headshake, Tankslappers?



2_SL0
3rd May 2005, 20:03
Before you say it, No we did not have the pleasure of experiencing a tank slapper. Infact I find the 636 extremely stable. However I am still running in and have not pushed the bike much at all. When I have opened it up I find I am ussually tucked in close to the tank sort of leaning over the front (crouched etc)
arms almost parrallel to the ground. (side note, I almost find it feels like Im sitting on the front wheel, wicked.) I try to be relaxed and not cling onto the bars to tight. On the FZ6 I did experience the occasional wiggle but nothing scary. ( I still have fond memories of tanks slappers on me dirt bike in the sand)
The occasional wiggle when the front gets light over a bump or 2 does not worry me. Tank Slappers DO. I have read (US sites, this could be the problem)
that a damper is very much worth purchasing. I do plan to buy one, but not till the end of winter. I have also read that the suspension setup and ride position will greatly reduce this problem. From what I have read with regards directly to the 05 636 the front setup has been adjusted from the previous 04 model to lesson theh risk of a tank slapper. I know these are sportbikes etc and it comes with the territory. So people with previous 636's and other supersports etc do you have a dampner, if not how have you found the bike etc? I would like some feedback on this as its something I am concerned about. Dont wanna end up in the ditch with me brand new bike.

Two Smoker
3rd May 2005, 20:11
My gixxer has a steering damper standard. It is an extremely stable bike, and i havnt had a shake on it yet. No shaking on it includes doing 260+ down Hunua Road and getting the front off the ground at high speed (180+)......

Compare this to F/F's R6 which has no damper... I had a couple of tank slappers on it the short time i rode it...

I highly recommend getting a damper... Cheap ones go for about 600-800 (Daytona and Hyperpro, WP) then Ohlins at about 1000+

Sensei
3rd May 2005, 21:03
Have found that Tank slappers only rear their head when you are pushing the bike over crests or uneven roades while on its side & powering out of corners have a standard one on the GSXR which does a good job for what it is . But would look at a better one when funds allow

madboy
3rd May 2005, 21:09
then Ohlins at about 1000+Haven't had the misfortune of a tank slapper yet, and I'm assuming the wheelspin and wiggle I got on the way to work in the wet this morning is not classified as a tank slapper. But was looking at the links on Feint's post the other night and they had Ohlins from the US for USD$480, which is a fair bit less than $1k. Would it be worth importing one?

I'm not in the market for one yet, way down my want list.

Skunk
3rd May 2005, 21:16
It can vary from model to model too; my ZRX1100 should have one fitted before doing wheelies, whereas the ZRX1200 doesn't need one at all...

I have heard (Trash will know better) that most Suzuki are better off with one, but Kwakas don't seem too need one as much.

At the end of the day - I know shit.

bugjuice
3rd May 2005, 23:33
I'm getting one, just saving.. I've had some good slaps around, and that was after I had decided to buy one. I've learnt to ride thru them, but I'd still prefer to have one rather than 'deal with it' so to speak.. kinda beats the wrists up

Waylander
3rd May 2005, 23:36
Ok so when I get mine I'm gonna plan on getting a damper for it.

idb
3rd May 2005, 23:36
I've met summa them tank slappers when I hang out at the wrong bars...
Yeah, OK, I just felt it was my turn

idb
3rd May 2005, 23:42
I read in some article written by some clever bloke that it is just a matter of changing the weight distribution on the bike.
So I suppose what that means is if you are getting tank slappers or shakes at the same speed, lean angle,whatever then maybe sit back or forward a little bit or maybe even simply lean forward a bit more.
Sounds easy......

Shawn
3rd May 2005, 23:54
Before you say it, No we did not have the pleasure of experiencing a tank slapper. Infact I find the 636 extremely stable. However I am still running in and have not pushed the bike much at all. When I have opened it up I find I am ussually tucked in close to the tank sort of leaning over the front (crouched etc)
arms almost parrallel to the ground. (side note, I almost find it feels like Im sitting on the front wheel, wicked.) I try to be relaxed and not cling onto the bars to tight. On the FZ6 I did experience the occasional wiggle but nothing scary. ( I still have fond memories of tanks slappers on me dirt bike in the sand)
The occasional wiggle when the front gets light over a bump or 2 does not worry me. Tank Slappers DO. I have read (US sites, this could be the problem)
that a damper is very much worth purchasing. I do plan to buy one, but not till the end of winter. I have also read that the suspension setup and ride position will greatly reduce this problem. From what I have read with regards directly to the 05 636 the front setup has been adjusted from the previous 04 model to lesson theh risk of a tank slapper. I know these are sportbikes etc and it comes with the territory. So people with previous 636's and other supersports etc do you have a dampner, if not how have you found the bike etc? I would like some feedback on this as its something I am concerned about. Dont wanna end up in the ditch with me brand new bike.



Dunno too much about this, but mt. eden sold most of their 03 and 04 636 with Ohlins damper on them as mike reckons that’s really necessary on them…

And you can get Ohlins from them for 990.00 including fitting…

But personally im getting THIS (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=4526402600&sspagename=STRK%3AMEWA%3AIT) for US$510.00 or THIS (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=4527273417&sspagename=STRK%3AMEWA%3AIT) for US$315.00 (Doesn't come with any mounting kit...)

also both of them don't need any fairing modification or anything...
Shawn

crazylittleshit
3rd May 2005, 23:56
I was under the impression that the bike wants to go striaght at all times Iheard if you just let the bike do its thing it comes right. YET I HAVE NO EXPERIENCE.

Shawn
4th May 2005, 00:04
I was under the impression that the bike wants to go striaght at all times Iheard if you just let the bike do its thing it comes right. YET I HAVE NO EXPERIENCE.

hey dude nice profile pic?...how did u get it taken?...now don't tell me it's photoshop!!!..

Ixion
4th May 2005, 00:17
Fark. $1000 ! That's a lot for what is basically just a small hydraulic damper ! :gob: Surely there must be cheaper ones ?

'Orrible thinger tankslappers but, I hate them. One of the few things in motorcycling that scares me. Yeah I know, relax and ride it out. Sure, until it throws you right off. :eek:

erik
4th May 2005, 08:33
hey dude nice profile pic?...how did u get it taken?...now don't tell me it's photoshop!!!..
Yeah, it is a cool pic. Looks kinda weird though, almost like it's a computer generated image from a game or something.

bugjuice
4th May 2005, 09:26
There are cheaper dampers out there, plenty of them. But it's one of those things - you get what you pay for.. Mike was trying to sell me one when I bought my bike, but I had just blown way more than I wanted on the bike, then he was trying to get me to part with another grand for damper.. If I had the spare cash, I probably might have, but I've seen very good ones at $400 or so. I saw one with a speed control valve (so the fast the shake, the harder it dampens) at something like $580. That's probably what I'll be getting.

As for what causes it, playing with the suspension set up and tyres can help, but the main reason for the cause is too much acceleration and the front wheel starts to skip the road surface. Then it catches the road at an angle and rebounds back, but that's too much, so it bounds the other way and so forth, then you're a slapperin a way. A damper helps to slow down the side-to-side motion and regain control quicker.

MSTRS
4th May 2005, 09:51
I had a sealed, nonserviceable damper on the 1100 that shit itself. Straight away, I noticed the headshakes under heavy acceleration out of corners. Replaced the damper - voila, no more headshake. Guess it all depends on how hard you wanna push your bike as to whether you need a damper?

bugjuice
4th May 2005, 10:18
I had a sealed, nonserviceable damper on the 1100 that shit itself. Straight away, I noticed the headshakes under heavy acceleration out of corners. Replaced the damper - voila, no more headshake. Guess it all depends on how hard you wanna push your bike as to whether you need a damper?
and the kind of bike you have.. But yeah. If you seldom ride hard, then you'll probably never ever need one. But if you have a sports bike that's a bit twitchy and accelerates well (with sticky tyres), then you'd be better off with one. Lets face it, you have a sports bike, you wanna spank it now and again :yeah:

If I had a dollar every time I needed one, I'd have about 30 bucks at the moment.. but still, I'm saving.. :wait:

2_SL0
4th May 2005, 12:10
So here is the question, I was busy saving my dollers to buy some leathers. (I already have a Dririder jacket and pants etc.) but should I buy a damper first. Plus being winter the Dririder gear is going to be warner and more waterproof. So wait for summer and then buy leathers etc.

bugjuice
4th May 2005, 12:14
So here is the question, I was busy saving my dollers to buy some leathers. (I already have a Dririder jacket and pants etc.) but should I buy a damper first. Plus being winter the Dririder gear is going to be warner and more waterproof. So wait for summer and then buy leathers etc.
well depends on how you intend to ride over the winter. And how you have been riding. If you haven't got one yet, then do you need one right away? By buying leathers, this will increase your mentality on the track and road, so you will be riding that bit harder, which may give you more slaps.. Or just back off a smidge and play it safe until you get the damper. Coming into winter (despite what I just said), leathers could be a bit cold, and in the wet, a damper might come in handy..
You'll eventually have both, so I guess just buy one or the other and save again..

Ixion
4th May 2005, 12:31
..

As for what causes it, playing with the suspension set up and tyres can help, but the main reason for the cause is too much acceleration and the front wheel starts to skip the road surface. Then it catches the road at an angle and rebounds back, but that's too much, so it bounds the other way and so forth, then you're a slapperin a way. A damper helps to slow down the side-to-side motion and regain control quicker.

Dunno- I'm sure that causes them, but they can also (on older bikes anyway) just "grow". The bars start shaking to and fro , and the shake gets worse and worse until it's slapping side to side. Braking or deceleration makes it worse. :nono: Acceleration is supposed to be the cure, but it takes cast iron balls to turn up the wick when the front ends gone insane ! We didn't use to have hydraulic dampers, just the friction ones , winding them up tight helped. My old A10 was a beast for it until I rebuilt the steering damper, it had had a sidecar on it though, don't know if that had some effect.

I always blamed frame flexing , but that was probably just me parroting something I'd heard (from someone else who didn't know either :msn-wink: )

I imagine the underlying physics is probably the same though.

TwoSeven
4th May 2005, 13:30
I have always had a weird view on steering dampers - I dont use them, so probably talking bollox :)

To calibrate a damper you need to know how a head shake (it’s different from a tank slapper) occurs. Following is my theory.

Basically when the load of the bike is transferred from the rear of the bike (acceleration or in extreme conditions constant speed) to the front of the bike (de-acceleration), extra weight will be put on the front tire, especially if the front shock is not set up properly to slow this transfer down. What happens next is that the tire will attempt to deform in order to cope with the load - the lower the tire pressure the more it will deform and squirm about. When this happens your rake/trail is changing which causes the tire to try to turn around (and face the other way) or at least to start doing that – that causes the bars to oscillate. There are ways to induce this to make it happen, but I wouldn’t recommend it.

Anyhow, the role of the steering damper is to cope with this oscillation and slow or retard it. On the track there are two main causes – first one is under-inflated or cold tires (remember basic rule – 1psi expansion per 5deg in temp – depending on brand of tire – you’d know your rate based on your log book records). So many racers will drop a couple of PSI at the start of the race knowing that their tires will expand after a couple of laps when they get warm. Problem is, it increases the amount of deforming that tire will do when you promptly accelerate blindingly hard then wail on the front brake. Even if you do have the correct tire pressure, its possible to still hit the front brake hard enough and feel the front end moving around - that’s the second cause - just as well you hopefully haven’t got the biked leaned over or it will bin you rather quickly.

The trade off with a damper is that while it reduces front end head shake, it also reduces the amount of steering input and feedback you get. The other trade off that a bike that is not tracking properly in the front end, will not be able to go as fast around a corner as one that’s working nicely - you wont know this, because its masked with the damper.

The reason why I said I like freedom of movement on the road is because the road has way more bumps and potholes – if the front end cant move about and be deflected to some degree the force will go thru to the rider or somewhere else – sooner or later something will break - and sometimes will cause the next problem.

Out of interest, as far as I know a tank slapper is caused by the front end not being able to move about. Too hard a rider grasp on the bars or over tightened steering head, solid steering damper yada yada. What happens is the oscillation travels down to the back wheel (because there is nothing to absorb it), then comes back up the bike – sine waves are additive in this case so the amplitude doubles each time it goes up and down the bike. Eventually it ‘will’ force the bars to move but with sufficient force for you not to be able to do anything about it. It [the cause and effect] also happens blindingly fast although often you will notice that the oscillations are quite slow – sometimes you just get a nice little wallow or weave.

Anyway, once you know the point at where the headshake occurs, you need to increase the steering damper to limit that – but not too much that it causes high speed weave or a tank slapper.

Also, don’t confuse this with a light front end which is just the rider wiggling the bars or some minor muck causing interference under acceleration – that will go as soon as the front loads up again and damps it all out. Note, you’ll also get this kind of wiggle from too high a tire pressure and/or too steep a steering angle (high speed wobbles) which again if amplified can cause a tank slapper.

I’ve never really looked at the math for it (and I don’t want to ) – but that’s my theory of head shakes vs. tank slappers. It may be all woffle as far as I know.

MSTRS
4th May 2005, 14:10
It may be all woffle as far as I know.
Damn good read tho. :killingme
I've been led to believe that a steering damper shouldn't be able to be 'felt' in restricting movement - it's job is to slow the violent back/forward movement of the steering. Restricted ease of movement (by hand) is only necessary at track racing speeds.

Toast
5th May 2005, 18:19
Don't tank slappers also occur when the back wheel steps out and the front reacts to keep itself going in the same direction as the rear? I think I read that somewhere.

It all got put in to more understandable terms one night when I was coming back from Uni on the old CBRtwofiddy. I flicked it in to a roundabout (by the manly shops on the Whangaparoa penninsula) in the pouring rain at about 50 or 60km/h (feeling right brave that night I was), got the gas on, felt the back step out, and then nearly had my wrists broken by a massive $%^&'n slap from the bars...bike stayed upright, I probably looked like a legend (though no one was watching at 9pm), nearly dirtied my 'L' plates. Point of the story: seems like solid theory to me.

Two Smoker
5th May 2005, 18:47
Don't tank slappers also occur when the back wheel steps out and the front reacts to keep itself going in the same direction as the rear? I think I read that somewhere.

It all got put in to more understandable terms one night when I was coming back from Uni on the old CBRtwofiddy. I flicked it in to a roundabout (by the manly shops on the Whangaparoa penninsula) in the pouring rain at about 50 or 60km/h (feeling right brave that night I was), got the gas on, felt the back step out, and then nearly had my wrists broken by a massive $%^&'n slap from the bars...bike stayed upright, I probably looked like a legend (though no one was watching at 9pm), nearly dirtied my 'L' plates. Point of the story: seems like solid theory to me.

Ive never had a tank slapper from sliding it (whether it was a similar account of yours, or on the track at speed...) Tank slappers happen when the front wheel lands slightly a-scew (wheelie or front skips because of speed) and then progresses its servareness...

Matt Bleck
5th May 2005, 19:20
Me Gixxer has a tendency to head shake with the right ingrediants: hard acceleration, the front wheel getting lite, or hitting one of the many potholes on our roads. And each time I've kept the gas on and she's come right.

Toast
5th May 2005, 19:31
Ive never had a tank slapper from sliding it (whether it was a similar account of yours, or on the track at speed...) Tank slappers happen when the front wheel lands slightly a-scew (wheelie or front skips because of speed) and then progresses its servareness...

I'm thinking maybe it was a similar case to the phenomenon of just gassing it hard and lightening up the front...and maybe I rolled off slightly and that made it all worse...I dunno aye, was a long time ago now...I tend to take it easy in the wet, and am not keen to get the new bike wild at the rear yet.

sedge
5th May 2005, 20:15
I've got a theory too :) What causes tankslappers

I reckon it really has to do with a combination of gyroscopic force and deformation. (patrially ripping off the previous deformation theory, I have thought about this before though)

We all know that turning a spinning wheel produces force at a 90 degree angle to the spin right ? That's what keeps us upright on a bike, the force needed to overcome the gyroscopic force is greater than the force generated by the spin (of course put enough force in and you'll fall over)

This is also what allows us to counter steer, turning the wheel away from the corner will apply force to the bike to tip it into the corner in the opposite direction.

I get a wiggle under hard acceleration, this is normal. The real tank-slappers occur when you alter the geometry of the bike, EG you come over a crest, wheel goes light, then you land it, wheel slightly off line, the tyre compresses and deforms. Force is still applied by the bike moving forward, but the wheel is off centre, this causes same effect as countersteering with the handle bars.
Each time the tyre deforms it presses in to the road, then rebounds and lifts up, damping load is then over applied to the opposite side due to the lightness of the front end, the counter steering effect is amplified in the opposite direction. Repeat.

Dampers work because they are perfect dampers, people aren't, they have a inconstant damping rate, IE people react to each movement and under/over amplify. Tankslapper.

What do ya reckon ?

Sedge

sugilite
1st January 2006, 22:23
I've been buying steering dampeners for my bikes since the days of the dreaded 16 inch fronts.

I've had my fair share of tank slappers, even snapped a few steering stops along the way. I've never come off from one, but I've sure scared myself!
The last one was last year at manfield when my dampener broke of the frame (rivets broke) it started at the seal change just out of higgens and I did not gain control until 2 upwards gear changes and the 200 meter board for the sweeper, waaaaay to much time to think about it!

I use 2 techniques to get out of them and it depends on speed and circumstance as to which one I use.

Option one: slow speed - if you are on a reasonably powerful bike and you are in the lower gears, pop the front up and wheelie out of it. The last time I used this was on the 1st model TL i was test riding, it was before the recall done on that model to have steering dampeners fitted!
I was up mt vic in wellie, went to pass a bus load of jap tourists and it bloody tank slapped the length of the bus (I think they were quite excited with their birds eye view of it!), pulled said wheelie and re grounded the front wheel then pumped the brakes up again (more on this later)

Option 2 - high speed. Simultaneously lie on tank, clamp arms over knees (I'm tall, not sure how this works for shorter riders) to lower the CG forces and hold on tightish (hold on to loosely and you will snap your wrists like twigs) and accelerate as hard as you can, you may even need to change up to keep the acceleration going, never, never give up until it comes right (I was seriously looking at jumping ship for my last manfield one as I was not sure I was going to get it under control before the sweeper!), then pump the brakes.

What is this pump the brakes stuff?
Well, when you have a bad tank slapper, the front wheel twists against the brake calipers and opens up the brake pads within it, so after your 1st near heart attack moment, you get rewarded with a 2nd as you go for the brakes at the next corner! (yep, happened to me, and people thought the stain on the road was left by a sheep truck!)
For my worst slappers, I've had to pump the lever right to the bar 3 to 4 times to get them back!

My overall advice is, if you have a sports bike without one, and you like to ride fast....GET A DAMPENER NOW!
All it can take is a higher profile replacement tyre and that can be enough to alter your rear ride height changing your placid steering bike into a slapper!

Teflon
2nd January 2006, 12:39
Use to get shit loads coming out of corners from the front wheel landing crossed up, but i ride to slow to get them now.

Kornholio
2nd January 2006, 13:31
My 01 GSXR has one standard and I have had a few little wobbles but nothing like my 89 GSXR....that definitley needed one, had passed a car on a bridge once and when the front wheel hit the lip at the end of the bridge under full power the bars started shaking, I could hear the front wheel screeching on the road(I thought my arms were going to break) but I buttoned off a bit and all was calm until I came into the next corner and needed a bit of brake and there was nothing there.... Apparently the discs were warping and had rammed the pistons back into the caliper... a few pumps and all was good

This happened on several occasions but decelerating seemed to make it all better :D

boomer
2nd January 2006, 16:04
no major tankslappers for me yet, touch wood ( i know Dover i ride like a nana and im not likely too )

But i've had many a headshake from this old girl when powering down, usually in the straights..Scary enough, i hate to imagine what a tue tank slappers like :shit:

NhuanH
2nd January 2006, 20:25
...
However I am still running in and have not pushed the bike much at all.
...
I do plan to buy one, but not till the end of winter. I have also read that the suspension setup and ride position will greatly reduce this problem.
...
Have you run it in yet? Cos I think there is still some sort of limiter on it. :weird:

Ask zapf about sportsbike suspension setup, I think he can recommend some people. Also, have you finished with those shithouse BT014s? I reckon that could be the root cause.

Huntaway
2nd January 2006, 22:07
I was experiencing some headshake from my R6 with hard bumps (corners and straights). My (amateur) analysis was it might be due to diminished castor when the front end was packed down. Increasing front spring preload to lift the front higher has virtually eliminated it. Increasing front compression damping and easing off rebound damping (to slow any packing up) has helped too, allowing me to ease off the spring preload a little. I've had to trade off a little front comfort with the settings but the handling is now much more consistent.

Firefight
2nd January 2006, 22:20
So here is the question, I was busy saving my dollers to buy some leathers. (I already have a Dririder jacket and pants etc.) but should I buy a damper first. Plus being winter the Dririder gear is going to be warner and more waterproof. So wait for summer and then buy leathers etc.


hey Paul,

my advice buy the leathers first,

I'm on my third R6 as you know, I get a few slapps from time to time, none of my R6s have had dampers on,(you know how I ride, and what road I ride on the most) its a fact of life,
I do plan to get a damper one these days, just not sure that it that high a priority for me.

The first time it happened I shit myself,not sure what you are ment to do, I just gave it full gas and held on, that's pretty much what I do anytime it happens now.

good luck


F/F

idb
2nd January 2006, 22:24
Shagged rear shockies or a rebound setting too soft can cause them.
They rebound too much and steepen the steering angle.
Accelerating causes the rear to squat again and shallow up the steering angle again.
Changing weight distribution by shifting forwards or back can help as well.
Or so I read......
If you get them regularly I'd suggest check out the condition of the suspension and maybe lower the rear ride height or raise the front.

2_SL0
3rd January 2006, 19:07
I though I better do a update as someone has resurfaced this old thread. Dave (FF) thanks for the advice, I went with the leathers in the end. I just updated two a two piece Spyke set. Very pleased with them. As for the damper Ive drawn the same conclusion everyone else has. Yes I could put one on, but to tell the truth I havent found the bike that bad. I have had the odd wiggle, but I just let it wiggle and open up the gas. Im very pleased with the bike and the damper doesnt seem as important as before.

2_SL0
3rd January 2006, 19:13
Have you run it in yet? Cos I think there is still some sort of limiter on it. :weird:

Ask zapf about sportsbike suspension setup, I think he can recommend some people. Also, have you finished with those shithouse BT014s? I reckon that could be the root cause.


Hmmm, you found your midrange yet. I dont need high rpm as I have MIDRANGE POWER. :moon:
Yep those crappy Bt014, damn that tyre I blame it for everything :Pokey: , I went thru two sets before I realised Bridgestone had released a crap tyre. :Pokey:
I might look a combination of tyres, any ideas? :moon:

bugjuice
3rd January 2006, 19:14
good on ya mate..
have you got the suspension set up yet? I bet that'd take away at least half the slaps you get and make it an even better ride. I'm going to be doing mine soon, not touched since it came from the factory. I've read up heaps, and looking forward to playing. If you need to know anything I might be able to help with, then giz a shout ;)

Patch
14th January 2006, 16:09
i
hate to imagine what a true tank slappers like :shit:

I won't ride a big bike without a dampner anymore. I dropped my mate's RGV250 after wheeling it and come down crossed up. Biggest farkin' fright I've ever had. A severe headshake turned into a big mother tankslap (over about 60-70m) after I lost me balance :thud: from hitting a big hump in the road. A chap who helped pick me up off the road thought I was doing alright until the front wheel slid out and I came crashing down :blank:

If you are gonna ride hard or wheelie round the 100mph mark - get a dampner


So here is the question, I was busy saving my dollers to buy some leathers. (I already have a Dririder jacket and pants etc.) but should I buy a damper first. Plus being winter the Dririder gear is going to be warner and more waterproof. So wait for summer and then buy leathers etc.


I'd buy leathers first, dampner second. Dampners don't prevent skin removal in the unlikely event of a mishap. Up to you tho bro.