Wrenching on performance cars, particularly if you're involved in some form of racing, typically involves lots of parts-swapping. And whether this activity is motivated by upgrades or simply the need to replace what's worn out, at some point, new parts will find their way onto your car. For the experienced gearhead, the installation of these parts is often considered routine, although even veteran wrench-jockeys often overlook a critical aspect of the installation process: the break-in procedure.
We all know that new engines have to be broken in and new flat-tappet cams also require a dedicated run-in period, but what about the rest of the vehicle? If you had the opportunity to speak with the engineers who design parts for our machines, you'd soon learn that the importance of breaking in new components extends beyond the engine bay. We did just that, and consulted with some industry experts to get their advice on the areas that need attention and the procedures that will ensure the efficient operation and long life of the parts involved. You might be surprised at some of the things you've been overlooking.
BrakesAfter consulting with some experts, it became quite clear that the most commonly ignored break-in procedures are the ones involving brake parts. Replacing brake pads and rotors is a regular part of car ownership, even for those Camry-driving lemmings that clog up the highways. But most people, if they're even aware that brake pads must be broken in, consider this a race-only necessity. In fact, nearly all brake pads must be broken in for proper performance.
We spoke with Jay Buckley, one of the Bendix Brake Answermen, to gain insight on the subject of brake system break-in. Right off the bat Buckley reaffirmed that nearly all brake pads for all applications need to be broken in, or "bedded," before they will provide the intended performance. According to Buckley, semi-metallic brake pads-the type most of us use in our vehicles-have poor performance when they are "green," a term used to describe brand-new pads. The semi-metallics just don't stop well in their as-new state, which tends to provoke drivers to use the brakes harder in an effort to compensate. When this happens, the pads become overheated, which in turn boils the resins contained in the friction material, causing them to rise to the surface. These resins eventually solidify, becoming extremely hard and compromising brake performance while also inducing squealing.
Buckley tells us this is a common scenario, occurring as often as 8 out of 10 times new brakes are installed and not properly bedded. Once the premature overheating has taken place, the pads are effectively ruined and cannot be repaired. In fact, Buckley advised against the common practice of sanding the surface of the pads, largely because this is an ineffective method of saving the pads but also because it can pose a health hazard if the filings or dust particles are inhaled.
The issue is that the friction material in most brake pads requires proper heat cycling to fully cure the resins prior to any serious usage. Additionally, proper brake bedding involves depositing a layer of friction material on the rotor surface. Most do-it-yourselfers are unaware of this or simply disregard the manufacturer's recommendations, while professional mechanics often don't spare the extra time required to bed the brakes during the testdrive, if there even is a testdrive.
As Buckley says, the brake job is only as good as the mechanic doing it-proper techniques and procedures for the particular application must be observed to guarantee optimum performance from the system. This includes proper rotor resurfacing, proper rotor installation, correct wheel-nut torque (when using hubless rotors), and proper caliper slider lubrication, among other things. That said, Buckley went on to advise us on the proper procedure for bedding new brakes.