Suspension Guru required!

I'm throwing this one open but its a pretty specific question.

Rear Suspension chatter when hard on the brakes! How to get rid of it?

I've set the bike up so it rides superbly (GSXR K1 Ktek fork internals, WP rear) and the settings are about as nice as I'll ever get. But under hard breaking to slow bends (hairpins) the rear chatters.

Is there a way of reducing the chatter without adjusting the riding parameters? High speed compression/rebound damping?

The Hornet chatters like a gibbon and I presume thats due to lack of rebound damping. But the Suzuki's rebound is fab as it is. I don't want to increase it any more if I don't have to.

and I'll not be fitting a slipper clutch!

Any ideas?

C

[yorkie_chris]

Maybe you have too much rear rebound?

Strange, I was thinking too little!

C

[yorkie_chris]

So if back gets kicked up a little, too much rebound would hold it off the floor rather than it springing directly back into contact.

Remember rebound works both ways so if you back off rebound you will need to add compression to keep same low speed on that circuit.

Well too little rebound and it will mean that the wheel when compressed fast will extend back out too fast causing a hammer effect, or at least I visualise it like that, or with a lightened back end simply extend fast enough to have a pogo effect, throwing the back end in the air.

Think about having too much rebound and you will get it not extending fast enough which shouldn't really effect braking, in that it would simply mean the wheel loses contact with the floor momentarily. Though that happening when the brakes arnt strong enough to keep the bike endoing could cause it to crash back down. Though this would also probably mean you had issues when on the power as it would compress and then not get back in contact with the ground fast enough over bumps and would cause you to lose grip, again that's how Id visualise it.

See which one may fit what you feel... then my suggestion, play with the setting on it, but of course make sure you know how you got it at the moment so if you muck it up more you can go back to how it is now.

I set mine up how I like by thinking about what sensation I didnt like and visualising what might cause it, and then what might fix it. Often worked out!

Suspension is often hard to get right, especially riding fast like you on a track. Different people like different sensations, so testing is the only way to be certain imo.

Hope that helps some mate!

[yorkie_chris]

Only solution will be to try more rebound and see if it improves, then try less, see same.

If no improvement found anywhere then there must be some problem in valving, or maybe it is perfect and you need to buy a slipper clutch, which will break

Originally Posted by yorkie_chris

Only solution will be to try more rebound and see if it improves, then try less, see same.

If no improvement found anywhere then there must be some problem in valving, or maybe it is perfect and you need to buy a slipper clutch, which will break

Exactly how I see it. Though too much compression over bumps could also cause issues lol

Well then, there's an excuse to book another track day

As I visualise it, if something is occilating between two points (chatter), the way to stop it doing so it to dampen it (more). If it can't occilate as quickly then the frequency will change and lessen the chatter.

But on these new fangled shocks with high and low speed damping changing the high speed damping would seem the way to cancel it as chatter is a high speed movement (all be it over a small distance)

Fiddlin' time!

C

[Sid Squid]

Suspension terms are so subjective and my suggestion is based upon my understanding of your description.
But, assuming I correctly understand the problem you're having:
Is the problem apparent on all surfaces while braking hard? if so then I'd not look to damping first, I'd suspect the rear preload is too high and the suspension is topping out and unloading the tyre.

Maybe.

[rictus01]

Originally Posted by Sid Squid

Suspension terms are so subjective and my suggestion is based upon my understanding of your description.
But, assuming I correctly understand the problem you're having:
Is the problem apparent on all surfaces while braking hard? if so then I'd not look to damping first, I'd suspect the rear preload is too high and the suspension is topping out and unloading the tyre.

Maybe.

the solution would be ....... a pillion then.....


Cheers Mark.