Car: 2006 Chrysler 300C SRT-8 "Black Beauty II"
Join Date: Aug 2004
Location: Ottawa, Ontario
Thanked 400 Times in 314 Posts
Well as one with a lot of ice racing and winter rallies (in the past), I will say this:
Even the best ice tire will have little grip going downhill on ice - especially ice under a light dusting of snow on top. The ABS can make a lot of noise under those conditions.
If, after a brake inspection for, as MD says, a rock caught in the pad, you still see no explanation, take the car to a large open parking lot, under wet or ice conditions and try a few panic stops.
If the ABS feels okay, then it was probably just one of those rare situations where ice tires and ABS were overcome by ravity and the elements.