In the past I tried using both brake cleaner and a wire brush and thought I had it licked. However the brake squeal has returned. I will be finishing up some ignition work on my friend's car on Friday, so I will try the heavy grit sandpaper approach.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member