i have this for a while since fitting new discs and pads then it got less and less over time and now no noise at all - I have a hunch that its the pad was not seated correctly or maybe there was some kind of imperfection on the disc which has now worn down... it only did it when the car has been on a long journey and i turn right at slow speed, there is a long groan then gently tapping the brakes it disappears.