[mw9]

only thing that is mentioned in the F90 bulletin, about the brakes.

*The
diameter
of
the
rear
perforated
M
compound
br ake
disc
is
35 mm
larger
than
that
of
the
550i.
The
rear
brake
caliper,
apart
from
the
blue
paint
but
including
the
electromechanical
parking
brake,
was
taken
over
from
production
vehicles
and
is
a
singl e-piston
floating
caliper.*

Doesnt give any reason. I like the brakes on my M3 but the rear brakes never really bother me on the M5, as long as they perform well.