Article > Tech

So Many Brake Pads, So Little Time

By Gary Goms

In today's market, friction materials are designed to accommodate the most specific need. An informed counterperson should be able to recommend the right pad for the right customer.

With the introduction of numerous application-specific and performance-enhanced brake pad materials into the jobber inventory, recommending a brake pad to fit a customer's pocketbook has become a somewhat thorny issue for today's counterman. After all, does today's soccer mom really need the high-dollar ceramic pads to shuttle her kids to sports contests or, for that very reason, does she need more safety than an average brake pad can provide?

In years past, our choices were limited to "premium," "OE-equivalent" and "economy" grades of brake pad materials. Today, a retail or professional installer might demand a pad that will eliminate the thick brake dust that accumulates on spoke-type alloy wheels. On the other hand, he might request a pad that reduces objectionable brake noise or a pad that will produce better-than-original braking performance. Of course, we'll always have the customer who wants an economy-grade material designed to milk the last gasp out of a wheezing old clunker!

Due to the introduction of ventilated alloy wheels and advanced friction materials, engineers have been able to reduce the rotating mass of most brake assemblies. Obviously, using a ventilated wheel to increase the airflow around the brake assembly will help keep it cool. Next, using an advanced friction materials also allows the brake to operate at higher temperatures. Last, anti-lock brake technology tends to distribute wheel-to-wheel braking stresses more evenly during emergency stops. The results are lightweight disc brakes that work very well under most conditions.

Unfortunately, problems develop when a brake assembly may be designed too small for specific situations, such as emergency vehicle or police service. In these instances, the major complaints will be poor braking and service life. In some cases, these issues can be addressed with improved aftermarket pads and rotors. In other cases, the vehicle will become one of those that require caution when recommending friction materials and replacement brake rotors.

Although the industry does have manufacturing standards for friction material in the form of the 'edge codes' found on brake pads, it's important to understand that friction manufacturers may use different materials and formulations to meet a particular performance standard. Back in the 70s when disc brakes were first introduced, conventional asbestos friction materials worked very well on the massive vented disc brake rotors in use.

When asbestos is used, the rotor itself absorbs and dissipates the heat generated during braking. When semi-metallic materials were later introduced and installed on some of these applications, many installers found, since semi-metallic material conducts heat better than asbestos materials, the brake pedal felt less responsive because the massive rotors ran too cool for the semi-metallic materials to engage under normal braking.

Also, with the advent of metallic linings, the brake caliper itself had to be redesigned to prevent excessive heat from being transmitted through the pad into the brake caliper piston and eventually into the fluid itself. During severe braking, this heat transfer could boil the fluid in the brake caliper which would cause a catastrophic loss of braking force. In most cases, a phenolic or "plastic" caliper piston is used to help insulate the brake fluid from heat transmitted by the semi-metallic pad.

Today, of course, we're looking at a much larger array of brake friction materials. When speaking of ceramic materials, for example, we must realize ceramic materials are not all formulated alike or formulated for the same purpose. Ceramic pads, for example, are formulated to resist wear and cope with extreme heat. Equally expensive materials can also be used to silence unwanted noise in other applications. Less expensive "organic" materials may also be used that will either conform to worn rotors or provide better pedal response on early disc brake applications. Whatever the case, it's important to remember that an inherent danger might exist in any attempt to substitute OE-spec linings with less expensive linings for particular applications.

Some pad compositions, such as ceramic, may not work universally well in all applications because of compatibility issues with the brake rotor. To illustrate, we now have a wide array of replacement brake rotors, including "white-box" replicas, coming into the market place, which may not be equal in specification to the OE-equivalent replacement.

Many independent repair shops, for example, prefer installing premium-line rotors with ceramic pads because they seem to have the least number of noise and pulsation complaints. In other instances, shops have found that when a ceramic pad is used for severe-duty applications, the pad might require a dimpled or cross-drilled rotor designed to vent gases that form between the pad and rotor during severe braking.

Although such a distinction might seem insignificant at the parts counter, it can become a major factor when the vehicle is hauling heavy loads or is towing a trailer in mountainous areas.

Regardless of composition, the performance of a pad is usually directly proportional to price. Clearly, when prices are reduced, one or more of the qualitative aspects of brake pad design are usually sacrificed. The lesser-priced pad, however, has a definite place in both the mass and price-sensitive markets. Sure, the homemaker doesn't need the latest in high-performance friction for her daily trip to the supermarket. But on the other hand, it's equally important not to underestimate the important of performance friction to the retiree who may be towing a fifth-wheel trailer home through mountainous terrain.

Several schools of thought prevail in the current brake service market. First: Many manufacturers, for example, feel it's sufficient to clean and lubricate the caliper guides and install new brake pads on the old rotors, providing no pedal pulsation complaints exist. Second: Because the price of new brake rotors has significantly decreased, many shops would rather replace than resurface some rotor applications. Third: Many automakers and friction material manufacturers now recommend on-vehicle resurfacing equipment. Fourth: It's extremely important to refinish the rotor as smoothly as possible and to remove microscopic iron particles by washing the brake rotor in soap and water.

With that said, it's important not to substitute OEM or application-specific materials with less-expensive materials. To illustrate, violating an OE specification by installing ceramic on the front and semi-metallic on the rear might negatively alter the brake coefficient of friction or braking "bias" between front and rear.

If, on the other hand, the installer or customer has a specific brake performance complaint such a noise or brake fade, keep in mind most aftermarket suppliers have improved pads available that address those issues while meeting or exceeding OE specs. Whenever addressing any application-specific brake issue, the most important item in your trouble-shooting inventory is the phone number of your brake supplier's technical department. If there's any question about a brake pad application or a specific performance or durability complaint, it's highly likely your tech department has a solution for that particular situation. Remember, a brake pad's failure to perform to expectations can be linked to something as simple as bad driving habits or a badly adjusted/inoperative trailer brake.

And most importantly, selling a brake pad designed for the application is much more than an economic choice; it's also a choice of safety and security for the driver, passengers and those who may be sharing the road with them.

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