New pads and rotors need a bed-in procedure, and skipping it is the reason so many people believe their new brakes are defective within a month. Glazing, hot spots, uneven pad deposits and the low-frequency shudder that people call warped rotors are almost never a rotor thickness problem. They are a friction transfer problem, and the bed-in is what prevents them.
What is actually happening: a modern pad works by depositing a thin, even layer of its own friction material onto the rotor face. From then on the pad is largely braking against itself. The bed-in procedure lays that layer down evenly at controlled temperature. If your first hard stop from highway speed happens before the layer exists, you get a thick patch of pad material welded to one part of the rotor, and every rotation after that you feel it through the pedal.
The procedure takes about ten minutes on a quiet road. Make five moderate stops from roughly 35 mph down to 5 mph, easing off before you come to a complete halt, with about 30 seconds of rolling between each. Then make five harder stops from about 55 mph down to 5 mph, firm enough to feel the pedal load but short of ABS intervention. You will smell the pads. That is normal.
Then drive for at least ten minutes without coming to a complete stop, so airflow cools the rotors evenly. This is the step people skip. Sitting at a red light with a stationary pad clamped against a 600-degree rotor is exactly how you create the deposit you just spent ten minutes avoiding.
Avoid holding the car on the brakes at a stop, and avoid the drive-through car wash, for the first 200 miles. Track compounds need a more aggressive bed-in than the one above, and the pad manufacturer's own sheet always outranks a generic procedure. If a pad ships with no instructions at all, that tells you something about the pad.
