Akebono White Paper / Ceramic Friction Technology

Optimizing Brake Performance

When driving an automobile, few performance attributes are taken more for granted than the vehicle’s braking capabilities.  Simply put, drivers expect their vehicles’ brakes to work every time, without exception.  In North America, however, customer satisfaction rests on more than just pure stopping power.  Brake noise, vibration and harshness (NVH), as well as brake dusting characteristics, are major considerations among virtually all motorists.

This situation has been exacerbated by consumer demand for more responsive, performance-oriented steering systems.  These provide a driving experience more akin to that found in Europe, but also result in the driver feeling any vibration in the braking system much faster than ever before. 

Akebono Corporation, backed by more than 70 years of brake design expertise, and the world’s other leading brake friction material suppliers have spent significant R&D and financial resources over the past 25 years to develop advanced non-asbestos organic (NAO) brake friction technologies that optimize NVH performance and minimize brake dusting.

A growing number of automakers, led by the Japanese OEMs, have recognized NAO ceramic friction brake pads are often the best option for smooth, assured, quiet braking under a variety of driving conditions.  In addition, it has helped them significantly reduce warranty costs by as much as 90 percent.

An estimated 40 percent of new vehicle models currently sold in North America feature NAO ceramic friction materials as original equipment.  Decisions to use other brake friction materials at the OEM level are often driven by pricing pressures, an ongoing trend among North American OEMs.

Brake NVH performance also is a top concern in the aftermarket parts industry.  Noise, vibration, roughness and brake dust concerns have historically been the greatest causes of customer angst after an aftermarket brake job, virtually always leading to frustrating customer “comebacks” to brake installers.

NAO ceramic friction technology entered the aftermarket during the last several years and today is considered the replacement option of choice among many aftermarket installers.  They turn to NAO ceramic brake pads for both maintaining the original equipment performance of a vehicle’s brakes and upgrading customers’ from OE semi-metallic and other NAO pads.

This trend is accelerating.  NAO ceramic brake pads are now the fastest growing segment in the aftermarket pad category.  According to industry sales projections, the ultra-premium brake pad segment – dominated by ceramic friction technology – will account for approximately nine percent of all aftermarket brake disc pad sales in 2003.  This figure is expected to grow to 18 percent by 2007.

Origins of NAO Ceramic Friction Technology

Today’s advanced ceramic brake pad technology was derived from extensive industry-wide R&D activities beginning in the early 1980s to develop asbestos-free brake friction materials.  At the time, a number of developed countries around the world had announced plans to ban the use of asbestos due to a myriad of legitimate health issues.  Akebono, Nisshinbo (NBK) and Sumitomo led an effort to develop asbestos-free friction products, focusing first on development of low-metallic steel fiber brake pad technologies.

Akebono sold its first low-metallic brake pad to Mitsubishi Motors in 1987.  However, roughness – a common concern with steel fiber brake pads during their early development – prompted Akebono to begin development of an alternative friction material with better strength, durability and friction characteristics.

In 1989, Akebono introduced the industry’s first NAO ceramic technology brake pad for mass production.  That year, contracts were signed to supply the product for the hugely popular Honda Accord and Toyota Camry passenger cars, many of which were sold in North America.  Not surprisingly, imitation products from competitors appeared about one year later, the result of aggressive reverse-engineering by a number of manufacturers who recognized Akebono’s technological breakthrough.

Domestic automakers first embraced Akebono’s innovative friction product in 1993, when Ford specified it for the Taurus passenger car.  The following year, Akebono started supplying General Motors for its growing lineup of light-duty trucks and sport utility vehicles, as well as cars.  A number of other North American OEMs currently specify Akebono ceramic friction materials for new vehicles, including Honda, Toyota, Mitsubishi, Nissan and DaimlerChrysler.  Akebono currently is the leading supplier of NAO ceramic brake pad materials to OEMs in North America with more than 25 percent market share.  The company also supplies friction materials for North American vehicles produced by Mazda, Subaru and Isuzu in Japan, as well as Volkswagen and Audi.

Aftermarket Proliferation and Confusion

The growing popularity of Akebono’s NAO ceramic friction products among North American OEMs and their Tier I brake suppliers has led to the introduction of a number of similar products in the automotive aftermarket.  Virtually every aftermarket pad manufacturer offers at least one designated ceramic product.   This has led to a degree of confusion among many distributors, installers and drivers, because there is no standard definition in North America of what constitutes a ceramic brake pad or one set of performance standards that distinguishes NAO ceramic technology.

Consequently, some industry observers have questioned the performance validation processes used by various friction material suppliers in order to enter the market so quickly.  Many aftermarket brake pads contain materials that meet the technical definition of ceramics to varying degrees, but their mere presence does not guarantee optimized NVH performance.  Ceramic materials are a core ingredient in Akebono friction products.  Furthermore, NVH performance is dictated by the careful formulation and interaction of all ingredients found in a brake pad.  Akebono formulations can be made up of 20 or more separate raw ingredients.

Depending on the marketer, a so-called ceramic pad also could be categorized as a NAO, low-metallic, semi-metallic or carbon-metallic product.  Akebono’s use of ceramic ingredients, however, is scientifically driven to ensure stringent physical properties like particle size, particle size distribution, shape, hardness and thermal characteristics are consistently delivered in many vehicle-specific ceramic formulations.

In head-to-head controlled tests comparing ceramic friction materials from a number of aftermarket pad manufacturers, Akebono’s ceramic technology assured performance far superior in a number of categories.  Not only was Akebono the clear choice in quiet braking, but it also demonstrated superior brake fade/recovery performance and more consistent vehicle brake system response and reduced pedal effort.  Akebono’s ceramic technology also demonstrated more consistent stopping power throughout the brake deceleration and speed range of typical driving conditions.   In addition, Akebono’s ceramic formulations proved to be more rotor-friendly.

Another key differentiator distinguishing Akebono ceramic technology from others is the world-class quality of the product.  The automotive industry’s Six Sigma quality standards allow for 2,400 rejected parts per million made.  Over the past several years, Akebono’s exhaustive quality standards have resulted in a reject rate of virtually zero at its manufacturing facilities in Kentucky, establishing a new quality benchmark.  Outside of Akebono, this consistency is simply unheard of in the aftermarket brake pad industry.

A key to reaching such strict OE quality standards is Akebono’s positive mold process.  It involves spreading the formulation mix more evenly with more consistent pressure versus the flash mold process used by other aftermarket pad manufacturers.  Flash molding results in inconsistent quality from batch to batch and pad hardness varies.  Another critical control factor in the Akebono manufacturing process is maintaining the appropriate moisture content of the formulation mix.  In addition, Akebono’s press cycles tend to be significantly longer to help ensure proper curing.

Performance Attributes of Ceramic Brakes

Refined over the past 25 years, Akebono’s ceramic brake pad technology offers a number of performance advantages over traditional semi-metallic and other NAO products.  Akebono’s advanced friction technology is carefully formulated to provide optimal NVH performance under a variety of driving conditions.

Elimination of Brake Squeal and Grinding

Akebono has developed hundreds of unique ceramic friction formulations for controlling and/or eliminating brake NVH issues – many of these for specific vehicles.  Akebono’s typical NAO ceramic friction pad contains an average of 20 raw ingredients, whereas a semi-metallic friction formulation may have no more than eight.   Each Akebono pad application features carefully engineered, scientifically applied chamfers and slots to reduce and/or eliminate noise.  Precision-fit shims are incorporated into the design to eliminate noise as well.

Mu (Friction) Stability

Akebono ceramic brake pads provide increased Mu friction stability (consistent stopping power) in critical braking situations, while semi-metallic pads lose their effectiveness in panic stops.  There is a small variation in the friction stability of Akebono pads between a normal stop and a panic stop.  In identical situations, semi-metallic pad performance can experience a variation of up to three times more, which equates to a loss of more than 1/3 of the brake’s stopping power.  This less predictable stopping power often leads to customer comebacks due to perceived brake fading.  Ceramic friction technology provides superior vehicle control, driver comfort and safety over a wide range of driving situations – maximizing driver confidence.

Ultra-Low Dusting

Another significant customer complaint in North America associated with brake performance is wheel dusting, especially involving semi-metallic pads.  The materials found in Akebono’s NAO ceramic brake pads are more compatible with today’s popular aluminum, open-wheel designs.  Carefully chosen raw materials also are used to help eliminate the appearance of dusting.

Improved Pad Wear

For the vast majority of drivers, brake pad temperatures climb no higher than 250 degrees Celsius.  Under these conditions, Akebono’s NAO ceramic friction technology provides significantly improved pad wear performance compared to semi-metallic products.

Minimization of Rotor Thickness Variation

Rotor thickness variation and resulting pedal pulsation are also minimized through Akebono’s ceramic technology.  Akebono’s patented friction material formulations include uniquely shaped ceramic particles that are less abrasive to the rotor surfaces.  In addition, Akebono pads tend to contact the rotor in a more adhesive fashion to slow the wheel as compared to semi-metallic and other NAO pads that are much more abrasive, attacking the rotor and producing significantly more brake dusting.  This unique approach reduces rotor wear by as much as 80 percent, thus increasing rotor life by as much as 400 percent versus semi-metallic and other pads.

The Next Breakthrough

Compared to semi-metallic pads, NAO ceramic friction technology currently is not optimized for extreme driving conditions, where brake temperatures can reach 300 degrees Celsius or higher.  Akebono thinks the next major advancement in NAO ceramic technology will undoubtedly address high-temperature, severe-duty conditions.  The goal is a hybrid NAO friction formulation that provides consistent stopping power in performance situations that also controls or eliminates NVH characteristics.

Source: Akebono Corporation