Physics question

[Juanfer]

[KevinC]

Yes, it makes a difference. They are two different adjustments - compression and rebound damping. The top one, or the one on the external resivoir if you have that type, is for the compression damping. The bottom one is for the rebound damping.

One thing to keep in mind is that shocks off other bikes are usually set-up for suspension linkages with different ratios than the GS. Most are under-sprung and under-damped (any GSXR shocks) when installed on the GS. They really should have a different spring, and have the damping re-valved internally.

The damping adjustments available through the knobs are just for a very narrow range around the set point of the internal valving.

http://www.ohlins.com/mc_manuals.shtml

[The Buddha]

Cant see the bottom too well but....
Top is preload, bottom is ride height... very different things.
Cool.
Srinath.

[Juanfer]

Hummm....very good point. That explains a lot....now that you say it sounds very obvious...thanks...I wonder why I havent figured it out before....

[Bob Broussard]

The collar on the top of the shock adjusts spring preload. Other than that I don't see any adjustments. It doesn't look like it's adjustable for ride height on the bottom. And there are no compression and rebound adjustments I can see.
Adjusting the spring tension (preload) will effect the way the shock feels.
And will effect damping even if it is preset. If there are damping adjustments, they need to be changed when more/less preload is  added/subtracted.

[Juanfer]

[KevinC]

I should have looked at the photo - there are no damping adjustments on that shock.

[john]

Yep.  Preload affects ride height.  A stiffer spring will not compress as much as a softer spring.  So when the preload gets cranked up the bike won't squat down as much when you are sitting on it.

[KevinC]

Pre-load does not change the spring stiffness!

Preload is just that - it is the amount of load on the spring before the weight of the bike and rider come on to it. The spring stiffness can only be changed by replacing the spring.

Pre-load does effect the ride height, in fact that is about all it does. But there is one difference between pre-load and ride height adjustment - preload changes the ride height by adjusting where in the shock throw the bike rides. Too much pre-load will result in the shock topping out, too little will let it bottom easier Typically, with the proper rate spring, you want to have the pre-load set so you are at about 25% of the total suspension movement form the top, with the loaded weight on the wheels.

Ride height adjustment changes the ride height without affecting where in the suspension travel the bike sits.