Nothing at all. The preload affects only the loaded ride height. You need to set it so that when you are sat on the bike the shock is compressed about 1/3. We ask for your weight when you order, so we can will set it like this for you when we build your shock. You may want to adjust it when you have a pillion on, but pretty much all of your adjusting will be done via the damping knob.
On the threaded Preload adjusters if it is alll the way tight or loose what will it do to the damping?
Nothing at all. The preload affects only the loaded ride height. You need to set it so that when you are sat on the bike the shock is compressed about 1/3. We ask for your weight when you order, so we can will set it like this for you when we build your shock. You may want to adjust it when you have a pillion on, but pretty much all of your adjusting will be done via the damping knob.