I've made a photo of the actual "thing" as I find it very difficult to explain otherwise:
I'm wondering what this "thing" sets and how it actually works. So, what is "preload" and what happens when I turn it clockwise (plus) and anticlockwise (minus). I tried rotating it both ways to its maximum limit and I didn't notice any change in anything.
The bike the photo has been taken from is Merida Matts 40-D.