What exactly causes tank slappers

[Freak]

and can you set a bike up to prevent them :confused:

[johnr]

no single cause, its just a symptom of some instability, though it could be the wrong steering geometry, if you put longer/shorter shocks/forks on a bike and bollox the handling up, then again it can be a symptom of poor weight distribution, do you really need that anvil in your topbox? or simply worn or under/over inflated tyres, of worn suspension/steering components. finally, it could just be poor design (tl thou suzuki anyone?) or a combination of any of these mixed in with a dash of poor road conditions/surface, excess speed, bad riding etc, in short anything, everything, and sometimes nothing. steering dampers can take the sting out of them, but are really a mask over the problem rather than a cure for it, instability causes over sensitive steering, damper gives the steering a bit of firmness. take a look at a sidecar outfit, almost every one i know has at least one steering damper, my old bmw had two! fitting the chair made them inherently unstable steering wise, the damper didnt cure the problem, it just removed the symptom!!

[minxy]

I used to get the most HIDEOUS tank slappers on my first trike. It would happen whenever you took one hand off the bar. Took 2 steering dampers to bring it under control but, as john says, I suspect the frame work was iffy. The forks werent in great nick either. And on a trike, the front tyre didnt help.

Used to get it awful on my slabby too, usually when tackling high speed 'swoops' when there was less weight on the front and little rubber contact with the road. Jester could actually watch it weaving from behind - used to scare the pants off him. To me, it was all part of the bike but I was still relieved when it was cured by a new front end.

Now the gix is getting an USD front end, I am hunting for another steering damper. But I completely agree with John that a steering damper merely resolves the symptoms - an easy fix, if you like.

[Creature]

try here should expalin it for ya

http://64.172.168.34/neatstuff/rakeandtrail.htm

[Cook1e]

Ask one - plenty of tanked up slappers at this weekends SnT do!

[bill?]

What exactly causes tank slappers


only two things spring to mind.
1 wrong set up on your forks/frame
2 you ride like me, a complete wally :D

[Blackjack]

Well apart from the horrible fitting a steering damper option, this is roughly the way to go...

First ask yourself this question, is this an inherent thing with the bike, or is it a new development?

If it's inherent (you never heard anyone say how well a stock Z900 handled did you?), and the bike is stock then the chances are that either the frame is wobbly (older stuff) or the suspension settings need looking at. Possibly both!

Older jap frames benefit from bracing/replacing which helps keep everything lined up as it should be and that will improve things tremendously. Suspension settings, well the spring pre load isn't making the ride harder or softer, it's adjusting the rear ride height, which in turn is altering the trail. Same if you have pre load on the front forks, increasing the pre load raises the front, decreasing it, lowers it again altering the trail. That's the basics of it.

If it's a new development, then you might have fitted a tyre that's incorrect for the rim, or suspension components that are the wrong size (altering the geometry), wrong spring rate, wrong damping charecteristics. Retro fitting modern bits to an older barely adequte frmae can show up defects that were'nt apparent before.

Bear in mind that a full on race bike will tend to "shake its head" bordering on a tank slapper, anyway and as sports bikes push the envelope towards emulating full on race bikes, it's more likely to be something that you can induce by uninformed messing with the suspension, being over or under weight and about 200 other things.

[Freak]

Thanks for all the suggestions
It's certainly more complicated then I imagined
although I think Blackjack hit the nail on the head with
'uninformed messing with the suspension'
I'll pass the information on (with a small smirk on my face)
Thanks again

[Blackjack]

In that case if you've got an owners manual handy, that should give you data for the baseline settings. So reset EVERYTHING to what the manual reccomends.

From there you can fine tune it, BUT only alter one setting at a time!!!!!!