This might sound extreme but you can remove the pads and on the LEADING edge on forward wheel motion, grind a very small camphor, just a small 45 degree angle on edge. This often stops them squeking, and you are talking about a millimetre or two in lost pad area, which aint going to make any difference anyway, and the material is designed to wear away, so its not as daft as it sounds. Try that if you cant get rid of it any other way.