An emergency stop is no time for a driver to discover that his or her stopping power has been compromised by the vehicle's replacement brake linings. Unfortunately, drivers of vehicles using aftermarket replacement friction won't know if their new linings have diminished stopping power until a real-world situation puts them to the test. By then, it could be too late.
This serious safety consideration should not be left to chance. Fleet owners and operators can avoid reduced stopping power by replacing brake linings with those specified by the original equipment manufacturer (OEM). Committing to a like-for-like replacement is the only way fleets can maintain the same high level of safety NHTSA intended by mandating improvements in stopping performance. And it's a certain way to maintain compliance with new federal standards designed to improve highway safety.
Meeting New RSD Regulations
The first phase of stringent new federal Reduced Stopping Distance (RSD) regulations for Class 8 tractors went into effect August 1, 2011, with the second phase taking effect August 1, 2013. The requirements mandate a 30 percent reduction in stopping distance for over-the-road heavy trucks.
To meet the RSD standards, brake manufacturers have responded with high-performance foundation drum brake systems. The new brakes not only meet stopping distance requirements, they also perform better and with significantly less fade than their predecessors. These benefits extend to the OEM replacement linings designed for RSD-compliant braking systems. The high performance linings feature significantly higher stopping power, less fade, and perform significantly better than traditional brake linings. This means that they also maintain their performance levels much more effectively when subjected to the temperature increases that occur during demanding brake usage like carrying heavy loads, frequent stops, and operating in mountainous regions.
However, even as fleets and drivers have added new high-performance drum brakes to their vehicles, many remain unaware that the routine maintenance decision for specifying replacement friction can negate the technological advancements of the brakes, and potentially compromise safety. Relining today's high-performance drum brakes with typical aftermarket friction, and not the linings specified by the OEM, can significantly reduce a vehicle's braking capability and lead to longer stopping distances.
Demystifying FMVSS 121 Testing
In its recommended practices, the Technology and Maintenance Council (TMC) of the American Trucking Associations states, "It is essential that the replacement brake linings function as well as the material originally supplied on the vehicle."
When it comes to the average aftermarket replacement friction, these linings will likely not perform nearly as well as the original equipment. This reduced performance places these linings outside of the TMC's recommendations. Furthermore, the average replacement friction likely does not pass the higher vehicle performance requirements of RSD-level tests, even if it is Federal Motor Vehicle Safety Standard (FMVSS) 121 certified to the old standards.
Today there remains significant, widespread confusion about friction replacement related to the FMVSS 121 dynamometer test procedure, which is outdated in the new RSD environment. Unfortunately, passing this test is still considered by many to be a seal of approval for replacement linings. Results of the test are often viewed as an indicator that a brake lining will supply the torque output needed to stop a vehicle within the new standards, but this is not necessarily the case.
Bendix Commercial Vehicle Systems, a member of the Knorr-Bremse Group, develops and supplies leading-edge active safety technologies, air brake charging, and control systems and components under the...
Conclusions drawn from Bendix stopping-distance testing and analysis.