Last month i upgraded my front S3 breaks to the GT Brembos and at first i was very happy with them but a month on i'm not so happy. At 70MPH and above if i apply my breaks i seem to got a lot of feed back coming through the break pedal. And the faster i'm going (80-90 etc) and apply the breaks the worse it is. I spoke to the company who fitted them and they said my rear brakes where old and needed changing. I changed the pads to EBC Red Stuff but i havn't changed the discs which are about 9 months old and are Grooved Black diamond. I'm not a mechanic a need a bit of advice on this.Is it break Judder? Do they need to replace the discs? I've not raced the car i use it for work every day 50 to 250 miles in a day so i do take care. Many thanks for reading this.