I have seen quite a few posts about people adjusting the preload, and I have played around with the adjustment on mine. I decreased the preload on mine attempting to get a softer ride. It helped slightly but nothing major, but it also lost height and ground clearance. Had more issues during my riding style because of getting hung up on rocks and in ruts which outweighed the very slightly softer ride. On the other hand if you increase the preload it will raise the machine up but will cause a slightly harsher ride.
I'm sure somebody will chime in and say changing the preload does not affect the ride, but there is no way it can't. It does not technically change the spring rate but it does change the amount of force required to cause the initial movement of the spring. If you have linear rate springs of 300 lb/in then they are always 300 lb/in rate.........but the difference is in the preload. If you have 1" of preload that means you have 300 lbs. of force already applied to the spring (hence the term "preload") and this means it requires greater than 300 lbs. of force to start moving the springs. Now if you apply 2" of preload on the spring you now have 600 lb. applied to it (simple math....2" x 300 lb = 600), which means now it requires greater than 600 lbs. of force to start moving them. Basically the more preload applied the bigger bump or harsher impact you have to hit before the springs will actually start flexing.