2002 BMW M3: Breaking in the New Brakes
July 25, 2008
Before hammering on our new brake set up, Stoptech requires a relatively simple bed-in procedure. Pad-bedding demands a minimum of two series of ten partial braking events from 60 to 10 miles per hour. Each series is performed without letting the brakes cool between braking events. Then, after ten partial stops, the system is cooled to ambient temperature. After cooling another series is repeated. We performed two series of braking events.
This achieves two goals. First, it conditions the pad material by driving manufacturing resins out of the pads. Second, it creates material transfer to the rotor, which is essential in achieving proper friction characteristics for optimal performance.
In practice, this is a smelly, but necessary, procedure. About half-way through the first series of stops the pads begin to smoke something awful. Here's what they look like:
After ten stops we drove the car at high speed without applying the brakes until the system cooled down. Then we parked it for about 30 minutes before repeating another series of partial stops. This time there was no smoke. Pedal response and effort remained consistent throughout thanks to high-temperature fluid and stiffer-than-stock calipers. However, the heat shield on the right front began to rub when the system was hot. After removing the wheel, caliper and rotor we found this witness mark on the heat shield:
Using less-than-subtle motivation we were able to clearance the heat shield so it stopped rubbing. Really, it just took a couple thwacks from a rubber mallet to convince the shield it needed to give a few more millimeters of clearance.
Now we're ready to test. Look for that data on Monday.
Josh Jacquot, Senior road test editor @ 59,042 miles