Took my 2001 325Xi on the snow for the first time today and when applying strong braking pressure on snow or ice the brakes would emit a chattering noise, and the break pedal would chatter as well. This happened both with and without snow chains (with the chains on I had DSC off). It doesn't happen on dry pavement.
Anyone have thoughts on why this might be happening? I have snow tires (M+S on the sidewall).