Bedding is a "real conditions" heat cycle and the final step in
preparing the pads and rotors for service. All pads, even OE
stock replacement parts, will benefit from a proper bedding
cycle. All rotors, especially cast iron rotors that will be operated
at sustained high temperatures, will provide longer service life
and smoother braking when properly bedded. Bedding can be
done either in the vehicle, or on a special bedding dyno that
can realistically duplicate the torque loads, pressure, and
temperature that will be realized in the vehicle.
Rotor
Rotor Bedding
Rotor bedding is an essential element to high level
performance and durability. It is most critical with cast iron
rotors. Cast iron is extremely well suited to use as a brake rotor,
but it can be susceptible to thermal stress, distortion, and even
cracking if subjected to rapid changes in temperature when it's
new. The cracking sound that you may hear when pouring a
favorite beverage over a glass of ice is thermal shock. A proper
bedding cycle will gradually bring the rotors up to temperature
and then allow them to cool slowly and completely in order to
"season" and relieve any remaining stresses from the casting
and machining processes. With some compounds, a layer of
pad material may also be embedded onto the rotor face. It is
important that this "transfer layer" be deposited slowly and
smoothly. Otherwise, pedal pulsing and compromised friction
values can result.
Pad Bedding
The bedding process is the final "heat cure" for the pads. This
final bedding cure differs from an oven heat cure in such that
the oven heat cure does not include the pressure, torque, and
elevated surface temperatures that are necessary to properly
condition the pad for service. As it is with the rotors, new pads
must be gradually brought up to temperature and then slowly
cooled. If the pads are put into hard service right from the start,
damage from fractures or accelerated deterioration due to
extreme temperature variations between the surface and the
body of the pad can occur. Overall poor performance with the
potential for rotor damage are often the results.
Bedding Steps
Once the brake system has been tested and determined safe
to operate the vehicle, follow these steps for bedding of all pad
materials and rotors.
1. Begin with a series of 8-10 light stops from approximately
30 MPH down to 15 MPH allowing 20-30 seconds for
cooling between each stop.
2. Progress with a series of 8-10 moderate stops from around
45 MPH down to 30 MPH allowing a 20-30 second cool
down period between each stop.
3. Proceed with a series of 8-10 hard stops from 55-65 MPH
down to 25 MPH allowing 20-30 seconds of cool down time
between each stop.
4. Drive at a moderate cruising speed, with the least amount
of brake contact possible, until most of the heat has
dissipated from the brakes. Avoid sitting stopped with the
brake pedal depressed to hold the car in place during this
time. Park the vehicle and allow the brakes to cool to
ambient air temperature.
Notes:
During the bedding process, a more positive feel from the
brakes should develop. This is an indication that the bed in
process is working. If any level of brake fade is observed during
the hard stops, it may be an indication that the brakes have
been more than adequately heated. Begin cooling the brakes
with light driving and without brake contact immediately.
