Performance, service life drive product design.
Making sure that the brakes on their vehicles function properly is one of a fleet manager's primary safety concerns. While a number of factors contribute to brake performance, the impact of friction material on stopping distance puts brake linings at the top of the list.
Although brakes on new equipment must meet federally mandated stopping requirements (FMVSS 121), there are no such requirements for linings sold on the aftermarket. Most brake manufacturers and fleets agree that current friction codes don't provide a reliable measure of friction level. Consequently, TMC and SAE set out to develop a procedure for rating aftermarket brake linings. The result of their efforts is RP 628, which uses the test procedure from FMVSS 121 to certify aftermarket brake linings. Currently, about 40 aftermarket brake linings have been certified. While RP 628 is not the final answer to brake lining standards, most would agree it's a step in the right direction.
But while no one can deny the importance of brake performance, fleets are also concerned about service life, noise, and cost. Here's a look at some new developments in friction products.
As a result of corporate acquisitions made last year, Federal-Mogul now offers two groups of brake linings: Abex Friction Products and Ferodo Friction Products. New to the Abex line is the EXL Plus, which features a molded notch as a wear indicator. The presence of the notch means that at least a quarter of an inch of friction material is left. When the lining wear reaches the top of the notch, it's time to replace the brake shoe. EXL Plus is available on the 685 FF Supreme Brake Block (EXP) for GAWR of 23,000 lb., and the 6008-1 FF Premium Brake Block (ENP) for 20,000-lb. GAWR.
Federal-Mogul plans to give its Ferodo brand a facelift, which includes moving manufacturing operations to more modern facilities. In its efforts to market a strong family of Ferodo brake linings, some of the products will be reformulated.
As part of the trend away from asbestos brake linings, BrakePro developed a line of organic-based heavy-duty linings. Although these linings are available for a wide range of applications, BrakePro's product niche is the severe-duty sector.
The company's CM22A-1 product, designed for refuse, multi-stop, and on-highway applications, incorporates heat-resistant resins and friction modifiers for improved temperature stability. The result is longer service life and better fade resistance. For extremely heavy loads, BrakePro developed CM29, which handles loads up to 32,000-lb. GAWR on 18 x 7-in. brakes.
The development of new friction materials has been taken a step further with Carlisle Motion Control Industries' introduction of cohesive friction linings earlier this year. By creating a "transfer layer of nonabrasive particles that smear onto the face of the drum," drum damage and noise are minimized.
According to Carlisle, since the new material conforms to the drum, the amount of material in each brake lining has increased by as much as 10%. And the even distribution of heat over a greater area means that lining life is increased. Another advantage of cohesive friction materials is that they may make it easier to function properly even when a trailer is not fully loaded.
Dana Corp.'s chief engineer, Jim Clark, says the driving force behind lining design and development is service life since the longer linings last, the more they contribute to lower maintenance costs. Fleets have also pushed for wider brakes that will run cooler, providing "an exponential increase in lining life." For example, Dana has recently developed 85/8-in.-wide brakes that can get twice the life of a 7-in. brake. Currently, Dana's best-selling OE product is its ES (extended service) series, which provides the lining life that is so important to fleets.
At Haldex Midland Services (HMS), long-term R&D efforts are focused on building longer-life brake blocks. For the most part, extended-service products on the market today have gotten there by making them thicker, rather than using new raw materials. They caution, however, that new materials are likely to increase costs.
HMS offers brake linings under the Brake Technology and Grey Rock brand names. Their most popular product is the Grey Rock 20-20 Premium, a 23,000-lb. organic friction material that features long life without compromising performance.
Fras-Le North America entered into a strategic alliance with Meritor Automotive, giving Meritor exclusive rights to sell its brake linings. The Fras-Le product mix ranges from medium friction, asbestos-free linings for longhaul use to an organic premium product for severe-service applications such as logging and heavy construction. Fras-Le has two aftermarket products under development: a long-wear premium product and a material targeted specifically for the refuse-truck marketplace.
Recent developments at Meritor Automotive include building extra service life into its Q Plus drive- and trailer-axle brakes by using linings that have extra thickness at the maximum wear point. To address the problem of higher operating temperatures created by aerodynamic designs and increased workload, Meritor developed the Q Plus EX Package, which features a wider brake shoe. This configuration will help increase lining life, meeting fleet demands for lower maintenance costs and reduced downtime.