What's new in:Brake drums and rotors

Feb. 1, 2010
The focus on the new stopping distance standards might suggest that regulations are what drive research and development in the brake drum and rotor industry, but that is only a part of the story

The focus on the new stopping distance standards might suggest that regulations are what drive research and development in the brake drum and rotor industry, but that is only a part of the story. Along with tougher performance requirements, weight and cost are also continuing to push product development forward, especially during these tough economic times.


According to Jeffrey Geist, director of product and business development for Motor Wheel Commercial Vehicle Systems Inc., the new stopping distance requirements may be the No. 1 driver of development, but cost and weight are right behind. “The industry is responding to the new regulations by evaluating the technologies currently available to maximize performance,” he notes, “while still minimizing additional weight or cost.”

“Performance and life-cycle costs remain the primary drivers for the customer,” says Scott Osborn, director of product management for Gunite Corp. “The customer must determine what level of performance is desired and then choose the best brake products which deliver the highest value.”

Ken Kelley, vp for Webb Wheel Products Inc., agrees. “As we continue to endure a very difficult economy, fleets are carefully monitoring their cost per mile for each key wearable component,” Kelley notes. “Many suppliers are now offering a good/better/best approach to their brake drum product portfolio in order to suit the wide variety of applications seen today.”


When it comes to braking systems, weight and cost are inextricably linked. “Every pound removed from a vehicle's components directly relates to an additional pound of available payload,” observes Kelley. “There are many applications that leave a terminal fully loaded multiple times a day, and every pound counts.”

One of the ways foundation brake manufacturers are working to reduce weight is with new materials, particularly composites. But the newest materials are usually not the cheapest, so manufacturers (and fleets) are constantly dealing with the trade-offs. At Century Inc., for example, metal matrix composites are being utilized to produce lighter-weight brake drums.

“Century's light-weighting technology uses metal matrix composites (MMCs) to create strong, stiff, wear-resistant, vibration-dampened and lightweight components,” notes the company. “[We have] developed a proprietary process to mass-produce MMC materials. The representative component is a brake drum for a heavy truck that is 45% lighter than the standard drum.” Century displayed a military vehicle last fall which featured the new composite brake drums, and the company plans to develop a lightweight brake drum jointly with an as-yet unnamed vehicle manufacturer.

Like Century, ArvinMeritor has been working on alternative materials, such as aluminum metal matrix, carbon fiber, compact graphite iron and aluminum. The cost of such materials, however, remains a challenge. “These types of materials can offer certain benefits depending on the need,” notes Joe Kay, chief engineer, brake systems for ArvinMeritor. “Unfortunately, the cost of these materials is not at a level that consumers are willing to pay.”

“Cost is a major issue,” agrees Gerry Shroff, president of DuraBrake Co. “New materials [like MMC] may be ‘dream materials’ when it comes to weight savings, but they will increase cost and, at least for now, we do not think the industry will be willing to pay.”

Because of the cost penalties associated with new materials, some manufacturers have turned their attention to creating lighter-weight drums utilizing current materials and production technologies. Gunite, for example, offers a full-cast brake drum dubbed the “Gunite Gold,” which the company notes is “comparable in weight to steel shell composite brake drums.” Webb Wheel also offers a lighter-weight gray iron drum called the “Vortex,” which has a 12-lb. advantage per wheel end over standard gray iron drums. Motor Wheel's new CentriFuse Plus Long Life/Severe Service drums weigh “about 25 lbs. less than heavy-duty, full-cast drums,” according to the company.

Good old gray iron, as it turns out, still has a lot going for it as a material for brake drums. “Gray iron offers a very good wear surface, excellent thermal conductivity, very low thermal expansion, relatively low cost and many foundries can produce it,” notes Kay, “[but] the chemistry of gray iron varies between manufacturers. ArvinMeritor produces a gray iron chemistry that is designed to optimize the drum performance to how the brake is being used in service.”


While cost remains a steady pressure on fleets and their foundation brake suppliers alike, it does not let anyone off the hook when it comes to performance and product quality. Particularly since the recession, a number of new offshore suppliers have entered the U.S. brake aftermarket to mixed reviews.

“Asia has been changing the aftermarket landscape dramatically,” says Shroff, “but their cost advantage has diminished due to the relative weakness of the U.S. dollar and the increase in material costs for China. Product quality [from these new imports] has also been an issue because of inconsistency. There are some really good manufacturers in Asia now, but there are also still some substandard factories that give everyone a bad name.”

“There are concerns with any low-cost product,” notes Kay. “Making sure the chemistry is correct, no defects are in the castings, the proper drum or rotor is [specified] for the application and that the dimensions are correct is very important. If the drum or rotor doesn't fit correctly, it can lead to run-out problems. Incorrect chemistry usually can show up as cracks, excessive heat checks, warping, low thermal conductivity or noise.”

In the short term, at least, most brake suppliers see a continued period of steady evolution and improvement, rather than major shifts in braking technologies. “Current drum systems can meet the reduced stopping distance requirements,” says Motor Wheel's Geist, “and offer minimum additional weight and well-known maintenance practices.”

“Larger and/or wider brake drum sizes have been in production for many years and are commonly available in the North American market,” Webb Wheel's Kelley notes. “These larger drums will utilize the same maintenance practices used today for smaller brake drum sizes.”

“Brake drums and rotors will continue to be optimized for weight, and rotor designs will most likely evolve to improve durability and maintenance costs,” adds Gunite's Osborn. “Brake system suppliers realize customers would like the benefits of higher performance systems and are utilizing advanced development techniques like finite element analysis and computational fluid dynamics to reduce weight/cost, while maintaining a high level of performance. Advanced materials and improved test procedures also allow for further optimization. Ultimately, customer acceptance of the new systems will increase and prices will come down due to economies of scale.”












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