Freesync doesn't seems to work

I have a Gigabyte RX470 and an LG 23MP68VQ-P monitor. Freesync is enabled in the monitor and in crimson as well. I can not tell any difference in games if it's on or not. So I downloaded the windmill demo. In free sync range the screen is tearing a lot:

The range is 45-75 Hz for the monitor and it's only working over HDMI. Of course it's connected over a HDMI. (otherwise I couldn't even turn it on) What have I missed?