Originally Posted by
FBinNY
Keep in mind that you have no say in this. It's determined by the distance between the innermost sprocket and the spokes. If you feel the clearance seems too close, check that the hanger isn't bent, and the RD cage is straight.
That isn't true. On many hubs there is room to put a spacer between the cassette and freehub to move the low sprocket away from the spokes. I've done that with two 8 speed wheels I'm using with Mavic derailleurs that have rather thick inner pulley cage plates. 1mm spacers solved the problem with no other issues.
But a derailleur that is "too close" will pluck the spokes when climbing out of the saddle, announcing that it is "too close" without doing any damage. This is just one of those things where even the tiniest clearance is enough if there is no real way for the derailleur to actually hook a spoke - which requires considerable overlap. If the derailleur and spoke don't appear to touch in the stand and you can't get them to touch while climbing forcefully, there really isn't a way that they can interfere with each other.