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Brake
Fade Facts Go
to Seine Systems' Solution to Brake
Fade Download
Brake Fade Fact
Sheet Owners
of high performance vehicles are usually fortunate
recipients of pretty decent factory-equipped
brakes. Brakes, however, have thermal limits. These
limits depend on the amount of heat energy brake
components must deal with and dissipate. This in
turn relates to the rate of speed reduction and/or
the number of times this must occur from
speed. While
stock brakes are perfectly adequate, perhaps
overkill for "normal", even spirited street
driving, these same brakes used in track or
high-performance conditions can quickly reach their
limits especially when engine modifications have
increased the vehicle's speed potential. These
limits are the result of brake fade in one form or
another. Brake
Fade Pad
fade As
temperature increases, the friction material can
melt and the resins that bind the friction material
can vaporize and "out-gas". These vaporized gases
prevent intimate contact with the rotor which, in
turn, reduces friction. Some pad materials change
slowly at elevated temperatures while other
materials react with a sudden and dangerous loss of
friction. The result is "glazed" brake pads and
rotors. How
To Reduce Pad Fade? 1.
Organic Usually
light brown or tan 2. Semi-Metallic Light
tan with metal flecks to dark gray 3. Full
Metallic Dark
gray to black 4.
Carbon Dark
gray to black There
are trade-offs here. A less aggressive brake
material may be fine for normal street driving but
may be ineffective for repeated stops from high
speed. An aggressive brake material may be
ineffective when the brakes are not up to
temperature resulting in a loss of braking
effectiveness for street driving conditions but may
be just the ticket for repeated braking from high
speed. Green
Fade How
To Reduce Green Fade? Brake
pads will also bed-in faster if the rotor is not
shiny. Break up the rotor surface with a sanding
disc (approx. 200 grit) on a drill motor. As with
all newly installed brake pads, step on the brakes
to verify the pads contact the rotor surface before
you actually have to stop the car. Some
manufacturers have specific bedding instructions.
Here is one bedding procedure: a. At
a vehicle speed of approximately 50 mph, apply the
brakes while applying throttle to maintain vehicle
speed. Drag the brakes for about 8-10 seconds, then
release them. b. Drive
for about a minute to allow the brakes to cool,
then drag the brakes again for another 15-20
seconds. Brakes may begin to smoke and braking
efficiency may decrease slightly (green
fade). c. Drive
for a minute to cool off the brakes, then drag
brakes for about 25-30 seconds. d. Drive
for a couple of minutes to cool off the
brakes. e. Repeat
process 2-3 times. At
the track, do not apply the parking brake after
shutting down as this might warp the rotors. Try a
cool-down lap to allow the brakes to cool off.
After hard running, heat soak can damage the
caliper seals and warp the rotors. When
fluid reaches a critical temperature, it boils.
Regular brake fluids boil around 400ºF, the
best ones are stable up to 500ºF and higher.
Whatever the rating, when brake fluid boils, air
bubbles are created. Fluid in a closed system
cannot be compressed. However, air can be
compressed and the brake pedal and master cylinder
travel is used up compressing the air. With the
pedal travel thus taken up, the system is unable to
hydraulically move the pads against the brake
rotor. Since
brake fluid is hygroscopic (affinity to absorb
moisture), fluid (or rather the water in it) will
boil at lower temperatures. This is the main reason
to change fluid at prescribed intervals. How
to Reduce Fluid Fade? On
a street driven vehicle, change fluid every year
and top up using fresh fluid from an unopened can.
On a track car, change brake fluid and bleed the
system before each race. This schedule minimizes
the presence of water (and corrosion) in the brake
system, maintains the high boiling point of the
fluid and provides the additional margin to help
prevent fluid fade. |
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