As part of a continuous effort to increase highway safety and reduce the number of fatalities on America’s roadways, the National Highway Traffic Safety Association (NHTSA) introduced a new mandate requiring the installation of reduced stopping distance (RSD) brakes on new truck tractors (49 CFR Part 571; Docket No. NHTSA-2009-0083).
This mandate institutionalized an amended standard requiring “heavy” truck tractors to stop within 250 feet when loaded at their gross vehicle weight rating (GVWR) while moving at a speed of 60 mph.
The mandate further required “very heavy” truck tractors, which represent only a small amount (about 1 percent) of nationwide fleets, to come to a stop within 310 feet under the same conditions.
According to the mandate, all truck tractors must come to a stop within 235 feet when loaded to their “lightly loaded vehicle weight” (LLVW).
To meet the RSD requirements, manufacturers simply began installing larger brakes to energize the front axle of truck tractors. In years before, the majority of braking was controlled by the rear of the vehicle.
It is important to note that the NHTSA mandate only applies to brand new truck tractors at time of delivery. It does not apply to vehicles in service, nor does it require previously purchased vehicles to replace existing brakes.
Confusion
The mandate is causing confusion among many in the industry. Some industry brake manufacturers are using the RSD regulations as a way to gain business and marketing opportunities by making it seem as if brakes must be replaced with the OEM friction or friction with similar performance attributes to meet RSD requirements, which is untrue.
In fact, replacing existing brakes solely to meet RSD requirements may have a more negative than positive effect for truck tractor safety and performance.
Brake friction is an application specific product. Its performance is designed to match a vehicle’s duty cycle and operating environment.
Panic Brakes
RSD compliant brake frictions are meant to stop a truck tractor within distance regulations in emergency situations – also known as panic brakes – when applying full force at around 80 psi. Panic brakes are not necessarily crafted to operate ideally under day-to-day conditions, which usually see applications of no more than 20 psi.
Industry leaders have noticed that brakes that are installed to comply with RSD requirements have higher wear, frequently crack, make noises and cause vibrations.
Stopping distance is determined by much more than the type of brakes. Vehicle quality and age, tire pressure and the type of tires have a major impact on how quickly a truck will halt during panic brakes. While the type of brake certainly contributes, it should not be regarded as the lone factor in reducing stopping distances.
Used Trucks
Simply put, many truck part companies are using the new NHTSA mandate as a business opportunity to reel fleet owners in by providing them with the illusion that regular brakes must be replaced to RSD requirements. In reality, the mandate only applies to new truck tractors and RSD brakes can, in fact, be expensive and potentially destructive when installed on used vehicles.
Standard maintenance without the intent to abide by RSD requirements in used trucks is the less costly, logical solution.
Jim Reis is vice president and general manager of Stemco Brake Products Group (www.stemco.com). The company is a provider of the technology and manufacture of commercial vehicle wheel end, braking and suspension components, as well as intelligent transportation systems.
