First thing I'd do is call back, get that on a recording, and share it on YouTube and then with MB USA. I am pretty sure they'd get a large earful.

Second thing I'd do is find a good indy shop. Brakes are brakes. Sure, some newer cars have fancy carbon-ceramic two-piece setups, but a 560SEL's brakes are 4 wheel discs not too much different from any other 4 wheel disc setup from the 1960s to today.

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k