hmmm yeah the belt is loose enough but I noticed the sound when cranking it and looking was that it was coming from the front chain wheel, seems like when it’s wet it’s gripping onto the belt a little longer before it lets go. When it does it fast enough it seems to be causing the vibration. Once the entire thing is dried the grippyness disappears on the front chain wheel. Not too annoying since I’m a fair weather biker just a tad annoying sound when I gotta get home from the rain.