Brake Pads & Friction Material

Brakes mechanically stop your vehicle. 

When you put your foot on the brake pedal, hydraulic pressure is transmitted through the brake lines and the pressure moves the piston which mechanically pushes the pad or lining material against the brake rotor or brake drum.

Brakes turn kinetic energy into heat. 

Applying the brakes causes a speed loss in the vehicle because of friction between the brake lining and rotor or drum.  Friction generates heat and repeated stops or high speed stops generate massive amounts of heat.  Finned brake rotors move air through the rotor to cool the rotor.  Wheels are bolted to the brake rotor and through conduction the wheel also dissipates heat from the brake rotor.

Brake friction materials 

also typically need to exhibit long life, resist corrosion, have low noise, and be cost effective.  From a driver’s standpoint the most important aspect is that the brakes stop the vehicle predictably and without problematic brake fade.

Organic brake material can be defined several ways such as: containing carbon, asbestos, nonasbestos, Kevlar, ceramic, and other natural materials that have been resin bonded into a friction material. 

Asbestos Brakes

was a great friction material at an affordable price that operated quietly.  Unfortunately, asbestos fibers can cause asbestosis which can lead to COPD, lung cancer or mesothelioma.  All of these bad medical conditions represent the reason that asbestos brake linings are essentially a thing of the past with limited application into the 1993 model year.

In the old days, compressed shop air was used to blow off brake parts creating a huge cloud of asbestos fibers as mormal routine for the auto mechanic.  When asbestos medical problems surfaced because of the Occupational Safety and Health Act of 1970, with OSHA Regulations that ultimately changed operational procedures in the automotive brake repair department and clutch disk department and gasket department.  A lot of asbestos went into automobiles and some of that asbestos can still be found in automobiles.  In the link above, and repeated here, is an excellent NIOSH report from 1989 dealing with Asbestosis Exposure in Automotive Brake Service.  If you have ever been exposed to this hazard or you have a particular interest in this topic then you should review the article.

Brake pads today

fall into many different categories and definitions including: Original Equipment or OE, semi-metalic, Premium, Non-Asbestos Organic (NAO), Low-Metallic NAO, and NAO Ceramic.  Society of Automotive Engineers, SAE J-866a defines how friction materials should be identified when the friciton material is tested according to SAE J-886. 

When you look at the edge of the brake  lining material it will have a two letter code that corresponds to the normal friction level and one letter that represents the hot friction level.  If you are really into brake pads for ultimate performance then you will want to become very familiar with J-886a.  If you have concerns about big truck air brake systems then you will need to reference the Maintenance Council of the American Trucking Association RP-628 which relates to the Federal Motor Vehicle Safety Standard (FMVSS) 121 test procedure.

Brake Material Selection

Establish specific performance characteristics, such as low dust and reasonable price, and then research available technology and information.  Internet research will likely help to answer your questions and provide detailed assessments from individuals using that product.

Historical research comparison will help the proper decision to be made.  Police vehicles lead a very demanding performance life and therefore police vehicles have significant research documents that are available for brake component decision making.

At the High Performance Driver Training Program brake life was about one to two weeks.  This same time frame is also applied to a typical New York City taxi because these cars can stay in service around the clock.

It is critical from a safety standpoint that brakes work reliably.  However, special performance characteristics and the type of various friction materials available make for a challenging choice of replacement brake components.  Brake rotors and drums wear out and these must be measured and inspected for condition.

Decision Point

From a basic decision the answer is OE.  From an advanced decision you will have to start your search at this point.  It is a challenging objective.