I was always taught that 2/32 of remaining pad was where I could recommend pad/shoe replacement to customers. I know that most of the wear indicators that I've seen in GM products will start squealing with around 3/32 of friction material left.
That said, you'd have to ask a BMW service dept where the sensors were calibrated to come on.
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Monday, March 12th, 2012 AT 1:18 AM