I had the S20s on two of my bikes and both had the same problem. Tires wore too fast compared to the BT-016 and they followed the road grooves/imperfections way too much once about half the tread was gone. I pulled them early on both. I was so paranoid I went back the BT-016 Pro that was re-released instead of trying the S21. I rode on a set of S21s on a friends bike, but they were fairly new and worked fine.