Do your ZMs make a sort of hummimg noise when braking. I changed my discs and pads and it still does it so starting to think its just the noise it makes! Usually happens when applying soft to medium brake pressure. Cheers
There's a reference to the noise in the manual. Can't remember exactly where it is, but I'm pretty sure it's somewhere in the M specific section and I'm also fairly sure it specifically mentions it's caused by the holes.