[amancuso]

I was under the impression that the CBS brake counter was just a wild figment of imagination, but recently, it said I was within 1000 miles of needing the rear pads changed. I tried to reset it but it was "unsuccessful". I removed the right rear wheel to inspect, and sure enough, it was right. The pad sensor is triggered. I ordered new pads and rotors and will tackle this next week or the week after.

[Wires]

On my E92 it was pretty bang on. The car seems to learn from how much you use the brakes to give you the orange "estimation number". When the sensor trips, then it switches to red and starts counting down based on how hard you used the brakes.

I was really light braking on my E92 (mostly engine braking), and it's estimates were pretty darn close!

[Billfitz]

If the sensor trips you'll get an accurate estimate of how many miles you have left before the pads are toast. Otherwise neither the car nor you has the slightest idea. Since there are eight pads but only two sensors that's not a good situation. I inspect all of mine yearly, and I only drive 3500 miles a year.