[jayartibee]

So I came to replace my front pads as the wear indicator (front brake service) had been triggered.

Basically the outer 12mm or so of the faces of the front discs had corroded, both sides of both discs, and therefore the wear indicator had triggered much too early as the corroded part wears the pad away more quickly - and e90 wear indicators trigger at about 5mm

I've cleaned up the discs. Maybe I should've replaced them but hey ho. They're bedding in now but how to stop this from happening again? The outer part of the disc is doing the most work (hence fronts much bigger) but this corrosion had rendered the discs the same diameter as the rears. Interestingly they'd passed the MOT test with no advisory about six weeks earlier. The disc corrosion was noted a year earlier...