Under the Hood: Breaking in your brakes

McClatchy-Tribune Information Services

Oct. 8, 2018

Q: I recently had brakes done on my Acura and was told by the service advisor to drive gently for the first hundred miles or so. A friend told me this is all wrong and I should have done a half dozen or more hard stops to “heat cycle” them before normal driving. Who is right?

—Jill D.

A: This is a controversial subject, as the recommended brake bedding-in process can vary quite a bit between brake pad manufacturers and shops performing the work. Other names for the process are break-in, conditioning and burnishing. This procedure should be performed whenever new brake pads are installed, new brake rotors are installed or the rotors are refinished. Ideally, this is done by the brake installer prior to vehicle delivery, but it helps if the vehicle owner picks up the ball and follows up with gentle brake use for several weeks. Successful bedding-in promotes smoother judder/noise-free brake performance over the long haul.

According to Raybestos, a major brake parts manufacturer, a proper break-in procedure provides three important functions: “Physically and thermally converts the composition of the pad and/or rotor, smooths the asperities (roughness, unevenness) of the mating surfaces, and heat cycles the entire pad structure.”

The bedding in process basically involves transferring a very thin layer or film of pad material to the rotor surface. A typical recommendation is to find an isolated section of road and perform about six to 10 moderate slow-downs from 40 mph down to 10 mph, allowing the brakes to cool a bit between each cycle. Stopping fully isn’t recommended as the brake pads may imprint on the rotor, upsetting the even transfer of film. Some pad manufacturers go a step further with additional firmer stops to generate additional heat. Continuing to drive afterwards for a bit to allow a gentle cool-down is sometimes called for, as well as avoiding using the parking brake during this first phase (if appropriate/safe). Attempting gentle brake use for the next 300 to 400 miles is also recommended to fully achieve film transfer, although if a sudden/severe stop is needed, of course do so!

Q: While doing a little servicing under the hood I noticed my battery was sweaty and seemed warm, although I had driven on and off for about an hour before. I’ve never seen a battery do this. Is it normal?

—Collin W.

A: This doesn’t sound good! It’s possible your charging system is overdoing things and is somewhat cooking the battery. If so, it’s odd you haven’t seen either an illuminated battery or check engine light, but weirder things have happened! An over-charge condition can be easily confirmed by observing battery voltage, while running, either from an instrument panel gauge or a voltmeter placed across the battery terminals. Most charging systems top out at about 14.8 volts. A reading notably higher than this does indicate a problem with the voltage regulator. This part is typically contained within the alternator or the process is conducted by the PCM (powertrain control module). If an over-charge condition is occurring, it’s best to get it fixed right away to prevent possible battery and component damage! Rinsing the battery, the tray beneath and surrounding metal of any acid residue with a stream of fresh water would be a good idea as well.