[1990 944 S2]I removed my rotors (front so far) to do some general cleaning and inspection. Wow, to my surprise, look at this photo of all the crud and muck on the teeth of the speed sensor and sensor head (for the ABS system).Has anyone else noticed something similar on their cars before? I've only owned the car for a year, and I don't know the prior maintenance of this by the PO, but apparently no one before me has noticed it, or bothered to deal with it.I wonder at point this would have begun to affect the speed monitoring of the wheel?Anyway, I have begun to carefully clean off a few of the teeth, and the sensor, and you can see that in the second picture.