If any of you are getting a grinding noise while braking together with bad brake fade and you can see no obvious reason for it (i.e. worn pads) you may like to look at the inside surface of your brake discs. If budget discs have been fitted in the past you can virtually guarantee they will be badly corroded on the inside even if the outside surface looks in good order. I`m not sure why this happens only on the inside but having a little knowledge of casting techniques, I think it may be because during the manufacturing process, the inferior metal used in these castings have a lot of contaminates in them which rise to the top of the casting while cooling, the inside surface of the disc would be the top of the cast. This corrosion happens regardless of whether the car has been in constant use or not, the friction surface of the disc literally starts to come away to a depth of about 1mm. Some of the cheap discs you get on a certain auction site are not worth getting even if they have a brand name, I have found to my cost that they can often be counterfeit parts and thus will not last or perform as they should. Some of these discs can have a life of just 12 months or less. Just a theory!