I don't want to trigger another never-ending thread, but in research for
another forum I stumbled across this essay on brake pulsations at
http://www.powerbrake.co.za/download..._01_judder.pdf

It seems to pull together the cementite issue with the issue of disc
thickness variation and supports it with pictures. I've seen the individual
pieces in various places but thought this did a good job of making sense of
it all. There is also a good treatment of brake pad selection that mainly
reinforces my preference for staying with OEM.

Mike