Originally Posted by
spectastic
I bought this cassette 2 months ago, and the only time I actually used the 12 sprocket was when I discovered it made this vibration. Are you saying this is a manufacture quality control issue?
No, I'm saying without that information it would be the first thing I would check. I am still wondering what you mean by wobbling and suggest you check the cassette has no side to side play. Another possibility is a chain/cog mismatch. Even though SRAM is generally compatible with Shimano, I have come across some combinations that did not work (there is not a list I just stumble upon them from time to time ).