300SDL fan belt issue

[JDmills]

I replaced the original fan belt on my 300SDL earlier this summer, with a continental brand replacement. ever since then it has had a slight squeel/squeek.. that can only be heard up near the engine, not from the drivers seat, even with the door open.

I noticed that the flat side of the belt is not looking like it is "pilling" the way my old fleece sweater used to do..

any ideas? The tension sheaf seems to be strait and tight.. and the belt coming off looked to be fine, but I figured it was time to replace it out of general principal.