How do Brake Service Indicator/Sensors work?

[briandwlee]

My '08 X5 3.0si was in for service to replace a radiator and a rear view carmera, which was mulfunctioning. After replacing camera, software was updated or encoded.

When I dropped it off at the service department, front brakes had 6,000km left and rear brakes had 7,000km left. I picked up the vehicle from the service department, and suddenly the vehicle is displaying that front brakes have only 3,100km and rear brakes have 1,700km.

How come they've gone down that quickly?

Do the brake wear sensors and system calculate the service due every time I turn on the engine or do the sensors have two or three stages that triggers warning and display gradually decreasing number between the stages?

Following is a note from my service advisor.

- Regarding the brakes, it has both a wear sensor, and takes input from the driving profile. If the vehicle sees a lot of stop and start driving or lots of short trips (ie parking lot from the drive-through, parking to the shop, shop to the parking lot, parking lot to wash….) It will re calculate the anticipated distance before they are due. You will likely see a change in this over the next few days. -

So, it means it'll go back up to 6,000km and 7,000km in a few days?

Thanks.