Originally Posted by radiantm3
NO, the sound is from pebbles stuck between the brake heat shield and rotors. This is a FACT. This happened to another M3 as well as mine during a recent BMWCCA car control clinic. The parking lot had a lot of loose gravel.
The reason the sound sometimes goes away for a day or 2 and then comes back is because the pebble gets stuck (possibly near the brake pads) and dislodge once in awhile when you reverse. When it happened to my car, the sound didn't completely go away until about a month passed. I'm sure the pebble just got smaller and smaller due to friction against the rotor and finally dropped out.
i would love to think it is this ^^ what u stated, but then why do some other members say its FOR SURE from the e-brake spring or something?? and needs to be adjusted...confusing...are they just TWO SEPARATE issues but coincidentally make the same cow bell noise??