I just invested 1000€ in my modest car with new brake discs and pads from Brembo. Now I hear a grinding scrubbing in the back when driving when I brake it away. The Mech tells me that this is only the first layer on the disc that needs to be removed. That’s 3 days ago, it’s still there. Do I have to worry? Should I do a few full brakes of 150km/h?