I kind of was wondering this myself, the front KYBs don't seem awful (I've only had my machine for 2 weeks so hard to actually say) but the backs just feel awful for trail riding. I hate the machine bucking and it seems to be coming from the rear mostly and I'm thinking the self levelers are the culprit.I replaced all 4. What sucks is that the KYBs on the front are really a good shock, but they're pricey if you need to buy 2 for the rear, especially if you want to add in the JBS Eibach springs to match what I had on the front. I ended up just going 814 Trail series on all 4 corners and glad I did!