It's not a wear indicator. Discs lip when they wear as the pads are always slightly inset from the edge of the disc so that the pads don't lip.VRSteve said:In my garage I have a set of disks of HRH's mini.
The grove cut in the disk measures 8.4mm, the same as the minimum thickness stamped on the front of the disk.
I measured using a digital calliper, so I am MORE than happy that I'm correct in what I say.
The balance machining will be the same width as the disc at max wear so that the minimum amount of material can be removed from the disc (i.e. No deep groove which would weaken the disc). If it was any wider than the max allowable wear there would be the risk of the disc balance changing as it wore.
