Anytime you need to add additional subdivisions to only certain edges of a circle (not all edges) you wind up with a shape that's no longer circular when the sub surf mod calculates the curve between the newly added vertex and the original vertices.
Logically it seems that there should be a way to determine where that new vertex needs to be to make the resulting sub surf line appear circular. Unfortunately, as a human, it's hard for me to pinpoint that exact location by eye.
Is there a tool or command that re-circularizes the shape once I add my subdivision to my circles edge? Am I thinking about this the wrong way such that there's an alternative path that fixes the problem without this tool?
Thanks in adv.