Brake Pad and Rotor Bed-In
Procedures
Also know as Burnishing or Breaking
In
All
brake pads must be bedded-in with the rotors they will be used
against to maximize brake performance. Until they are properly bedded in,
your brakes simply do not work as well as they can. Proper
brake pad and rotor bedding improves pedal feel, reduces or eliminates brake squeal,
prevents (and often cures) brake judder, reduces brake dust, and
extends the life of your pads and rotors.
The bedding-in process involves a gradual build up of heat in
the rotors and pad compound. This process lays down a thin
layer of transfer film on to the rotor surface. Following the
bed-in procedures provided will assure a smooth, even layer of
transfer film on the rotor and will minimize brake judder.
Here are a few things to keep in mind when installing new rotors
and pads:
1. When
installing new pads, the rotors should be new or at least
resurfaced to remove any transfer film from the previous set
of brake pads.
2. It
is critical that the installer clean any rust, scale, or
debris from the hub mounting surface thoroughly and check it
for excessive run-out with a dial indicator gauge before
installing the rotor. Failure to have a flat, even,
and clean surface will cause the rotor to warp when it is
tightened to the hub.
3. The
new rotors should also be checked for excessive run-out using
a dial indicator gauge before the caliper and pads are
installed. If a rotor has excessive run-out of over .004"
(.10mm) it should be replaced. Using a
rotor with excessive run-out on the hub or rotor will cause
vibration and pulsation issues.
4. Failure
to follow these procedures may result in brake judder,
excessive noise, or other difficulties in bedding-in the new
brake pads. The pads need a fresh surface to lay down an
even transfer film. Residue from the previous pad compound
on the surface or an irregular surface on a used rotor will
cause the pads to grip-slip-grip-slip as they pass over the
rotor surface under pressure. The resulting vibration will
cause noise and telegraph vibrations through the suspension
and steering wheel. This vibration is known as brake judder
or brake shimmy. This is typically caused by an uneven
transfer film on the rotor surface or an uneven surface on
the rotor not allowing that transfer film to develop evenly. This is often misdiagnosed as a warped rotor.
5. If
you have just installed rotors with zinc or cadmium plating,
or if the rotors have an anti-corrosion phosphate coating,
you should postpone the bedding process until normal driving
has allowed your brake pads to polish the rotors clean and
removed all traces of the plating or coating. If your
new brake rotors have an oily anti-corrosion coating, you
should clean this off thoroughly with brake cleaning spray
and/or hot soapy water.
Bedding-in
new pads and rotors should be done carefully and slowly. Rapid
heat build up in the brake system can lead to warped rotors and
or glazed brake pads. Most brake pad compounds will take up to
300-500 miles to fully develop an even transfer film on the
rotors.
The bed-in procedure for street brake pads is as follows:
1. This
step transfers pad material onto the rotors.
Make 10 stops from 30 mph (50
kph) down to about 10 mph (15 kph) using moderate braking
pressure and allowing approximately 30 seconds between
stops for cooling. Do not drag your pads during these
stops. After the 10th stop, allow 15 minutes for your
braking system to cool down.
2. This
step completes the curing of the brake pad's friction
material.
Make 5 consecutive stops from
50 mph (80 kph) down to 10 mph (15 kph). After the 5th
stop, allow your braking system to cool for approximately
30 minutes. This completes the break-in of your pads to
the rotor surface.
During
Steps 1 & 2, a de-gassing process occurs which may produce
an odor coming from your pads as they complete the break-in
cycle. This odor is normal and is part of the process your pads
must go through to achieve their ultimate level of performance.
The odor will go away after allowing your braking system to cool
for approximately 30 minutes.
After the break-in cycle, there should be a slight blue tint and
a light gray film on the rotor face. The blue tint tells you the
rotor has reached break-in temperature and the gray film is pad
material starting to transfer onto the rotor face. This is what
you are looking for. The best braking occurs when there is
an even layer of of pad material deposited across the
rotors. This minimizes squealing, increases braking
torque, and maximizes pad and rotor life.
After the first break in cycle shown above, the brakes may still
not be fully broken in. A second bed-in cycle, AFTER the
brakes have cooled down fully from the first cycle, may be
necessary before the brakes really start to perform well. This is especially true if you have installed new pads on old
rotors, since the pads need time to conform to the old rotor
wear pattern.
As with any
new set of pads, do not tow a trailer or do any hauling during
the break-in period.
Full
seating of your new brake pads normally occurs within 1,000
miles.
Read
and understand these bedding instructions completely before
starting. If you have questions, give us a call or
email.