My experience is that they are machined incorrectly, so they are rough and noisy with many chains. I had mine on a racing wheel, and the drag was noticeable. When I back pedalled to slow down it popped and crunched something awful. I took it off and compared it to another brand cog, and it was clear that the machining was off. I replaced it with a less expensive Dura Ace, and that completely solved the problem. I deep sixed the Surly, and will never buy another one.