I know that this has been covered before, but I mean it as a oil viscosity matrix or something.

What I want of you, is to go to your bike, compress your front end let it bounce back. Does it come back up, to the settling point or it overshoots it then comes back down to it?

I have read that ideally it should come back to the settling point and stay there - no bouncing up and down.

What is needed is the spring rate (stock or something else?) and oil viscosity (stock is 10W).

With my setup:

0.9Kg/mm sonic springs
15W oil (fresh, changed it today)
It bounces up then down again, to settle.

I will probably try some 20W.

I believe its called front end chatter. Springs without decent damping (yes rebound) tends to do that. Very very very few bikes actually can take front end spring only mods without going into the chatter mode. Think about it. Stiffer springs are a cheap cheap (literally 0 cost) thing for the manufacturers to have done. They didn't on bikes that dont have real suspensions because a chattering bike is much much worse than a mushy one. And they thought is a 100lb chick buys this, she'd be thrilled with the pretty purple ... front end ... whaaaaaat.
Rebound is the most important control there is, and its also pretty hard to put in adjustments for.
Anyway, 20 wt may correct it to the point where its not affecting you.
Cool.
Buddha.

Quote from: lamoun on July 26, 2008, 10:42:12 AM
I know that this has been covered before, but I mean it as a oil viscosity matrix or something.

What I want of you, is to go to your bike, compress your front end let it bounce back. Does it come back up, to the settling point or it overshoots it then comes back down to it?

I have read that ideally it should come back to the settling point and stay there - no bouncing up and down.

What is needed is the spring rate (stock or something else?) and oil viscosity (stock is 10W).

With my setup:

0.9Kg/mm sonic springs
15W oil (fresh, changed it today)
It bounces up then down again, to settle.

I will probably try some 20W.

Ride it some before you you change the oil. The static test doesn't tell you much, what really matters is how it works for the riding you do, for the sort of loads you put on the suspension. When you're cornering hard you want the bike to feel settled and planted, not like it's moving around randomly on the suspension. It's a little hard to figured out on a bike like the GS, since it flexs more than a modern design does. It's never going to feel like a GSXR.

Quote from: The Buddha on July 26, 2008, 02:31:37 PM
I believe its called front end chatter. Springs without decent damping (yes rebound) tends to do that. Very very very few bikes actually can take front end spring only mods without going into the chatter mode. Think about it. Stiffer springs are a cheap cheap (literally 0 cost) thing for the manufacturers to have done. They didn't on bikes that dont have real suspensions because a chattering bike is much much worse than a mushy one. And they thought is a 100lb chick buys this, she'd be thrilled with the pretty purple ... front end ... whaaaaaat.
Rebound is the most important control there is, and its also pretty hard to put in adjustments for.
Anyway, 20 wt may correct it to the point where its not affecting you.
Cool.
Buddha.

What your describing is a lack of low speed damping, and will make a bike weave slightly or pogo through corners.  Chatter is very different, it's a high frequency thing that occurs when cornering at the limit of adhesion and the tire alternately slides and grips. Typically not a function of spring rate or fork rebound damping. More often related to chassis attitude, fork compression damping or rear rebound damping.
Even bikes with very sophisticated suspensions often have springs that are way off, and there's at least one bike with a budget suspension (Ninja 650) that has insanely stiff springs. I gave up long ago trying to figure out why the manufacturers pick the rates they do, maybe they just have a big dartboard.

Oh - OK. Chatter is not due to excessive pogoing ? which is a result of lack of damping ?
I thought it was due to too much spring and no damping causing the forks to top out causing it to rebound back into the compression area. Sorta like he described.
Cool.
Buddha.

Quote from: RichDesmond on July 26, 2008, 09:27:16 PM
<snip>
Chatter is very different, it's a high frequency thing that occurs when cornering at the limit of adhesion and the tire alternately slides and grips. Typically not a function of spring rate or fork rebound damping. More often related to chassis attitude, fork compression damping or rear rebound damping.
<snip>

OK After a little bit of research. There is a type of chatter that is dependent on chassis. There is also a chatter that is induced just by springs being too stiff. Forks that dive very very little under brakes in a straight line can be induced to alternately slip and grip by very slight imperfections in the road. Not saying that he's having that happen, just saying that not chassis related or related to anything much at all really, just stiff springs. No idea how stiff they need to be.
Cool.
Buddha.