TECH: BMW/MINI Brake Pad Wear Algorithm TSB


This week I received a Technical Service Bulletin (TSB) from BMW about  an issue with some 2011-2012 Mini models. The  TSB was titled “Erroneous Service Due” message for Brake Pad Thickness.”

The models in question display a message about brake pad thickness and the pads should be serviced soon. When the pads are checked they are above specifications for replacement.

Anyone who has driven and worked on older BMW brakes knows they have a wires sensor on the inboard pad. When the sensor contacts the rotor and breaks the wire, a light on the dash goes on. Simple and yet effective. For the Mini, the thickness of the pads is an estimate, no wear sensors are ever harmed.

On the Minis in the TSB, the brake pad thickness is an estimate made by a computer on the car. The mathematical calculation are made by the Condition Based Services Module (CBS). The CBS uses inputs like vehicle speed, pedal pressure and rotor temperature to determine pad thickness. I wonder if this system is smart enough to know if the driver has ignored the warning for too long and the backing plates are in contact with the rotor. Could this be admissible in court?

The solution is to re-flash/reprogram the CBS module with new software and a better algorithm to estimate pad wear.