Slipstream - May 2020

Mechanical Musings: Why Do Brakes Cost So Much?
by Ed Mullenix
Porsche’s brakes are notoriously
expensive. The brake system
performance has to match the
engine and suspension performance.
We are talking a basic 997 Carrera
with conventional brakes, not
the carbon-fiber discs and yellow
calipers, which are ozone-layer
expensive, but they are racetechnology
derived and will shove
you against the seat belt when you
mash on the middle pedal.
The material used on
conventional brake pads is a ceramic
compound, sometimes with copper
particles that somewhat resemble
cement, included to dissipate heat.
The brake system is an “energy
convertor” converting mechanical
energy, vehicle speed, and inertia
into heat energy when you apply the
brakes. The engine is also an energy
convertor converting chemical
energy (combustion of fuel) into
mechanical energy to propel the car.
There are several aftermarket
suppliers of Porsche-suitable brake
components, from your local
Porsche dealer (which is probably
the most expensive option) to places
like AutoZone or NAPA. Also an
option are wholesale suppliers to
the repair industry, which include
the original equipment supplier
brands and several other lower-cost
brands. My personal choice is the
OEM brand (Jurid, ATE, Brembo,
or Pagid). The type of car determines
which brand is available for that
26 May
application. I will NOT use brake
pads from places like AutoZone.
Included is a photo of an economy
brand brake pad that sheared in
two. The fact that the brake disc
had a pronounced lip on the outside
edge kept the sheared section of pad
from being ejected out of the caliper
and possible accident when the
pedal would have gone completely
to the floor.
Another controversy is brake disc
or rotor replacement. The
cast iron discs will erode
away material just as the
pads do. Typically, around
45k miles, the front discs
will have sufficient erosion
to produce a pronounced
lip at the outside edge of
the disc and develop a
contoured surface. This
interferes with the new
brake
pad, which has
a perfectly flat
surface. A new
pad installed with
a seriously worn
disc will allow
only the inside
and outside edges
of the pad to
contact the disc,
with seriously
diminished
braking efficiency.
Eventually, in 200
miles or so, the
pad will conform
to the old disc but
the results could
be disastrous if
you had to panicstop
before the
pad had seated to
the disc.
It is my
understanding
that the dealer
will try to
convince their customers to replace
the discs every time they replace
the pads. This is partly because
of liability exposure and partly
to pay the light bill. I try to be
judicial about replacing discs. A
slight lip and a minor contouring
is acceptable because the discs are
crazy expensive and the new pads
will seat in just a few miles. If you
live in Park Cities, where there is a
stop light or stop sign every other
block, it is not uncommon to need
front pads every 15k miles. The rear
pads seem to last a little longer.
Porsche has pad wear sensors on
each corner. If the pad wear message
or light comes on, usually there is
sufficient material for you to drive
another 500 miles or so, allowing
you time to schedule a visit to your
favorite mechanic.
Having fun!!! Ed