While looking over my bike this morning to see what kind of RD it had, I found the RD to be somewhat loose. I went to tighten it up (not sure on terminology, but it's the 6mm allen that the whole thing pivots on--the allen screws into the hanger piece that sits in the dropout), but found that it's actually a nut and bolt affair--the nut on the backside spins. I know this part needs to be a bit loose, so it can pivot; but I thought they were all tapped into the hanger? I'm going to try later on to tighten it; I'm hoping that the bolt has a shoulder to prevent it from being overtightened.