HeyI have recently had some very annoying troubles with my drivetrain, I know that it is the Surly Screw-On cog which is causing the problems. It seems that the chain cant flex up and down at all without it starting to skip. So basically I cant use a regular rear mech, I have to use this "thing". See the pic below. I also bought an 74kingz tensioner a few weeks ago, I hoped that I could use that but no. So I need to buy a new screw-on cog, but which one? I really do not want to spend money on shite this time. Please give me a few hints what to buy, preferably from tarty. Ohh, I need a 15thoothCheers, Sondre Edit:I am using this now: Tarty