A New Step on the Brakes

In July, the National Highway Traffic Safety Administration (NHTSA) issued a braking standard that effectively shortens the majority of large truck stopping distances by 30%. The rule applies only to new truck tractors; it does not impact single-unit trucks, trailers or buses.

The amended standard requires heavy truck tractors to stop in not more than 250 ft. (vs. the previous standard of 355 ft.) when loaded to their Gross Vehicle Weight Rating (GVWR) and tested at 60 mph. For a small number of very heavy severe-service tractors, the stopping distance requirement is 310 ft., under the same conditions. In addition, all heavy truck tractors must stop within 235 ft. when loaded to their lightly loaded vehicle weight.

The standard will be implemented in phases. Three-axle tractors with a GVWR of 59,600 lbs. or less must meet the reduced stopping distance requirements by August 1, 2011. All other tractors must be in compliance by August 1, 2013. Voluntary early compliance is also permitted.

Solutions available
The NHTSA claims there are simple and effective solutions available to meet the new requirements, including enhanced drum brakes, air disc brakes or hybrid disc/drum systems. Such systems are already in use on a number of vehicles in the current commercial fleet.

One example is the ArvinMeritor line of Q Plus drum brakes. "ArvinMeritor has been on a reduced stopping distance program for over three years in anticipation of the new regulations," says Mike Pennington. "As a result, the Q Plus product will meet the new requirement with an additional 10% margin."

"It's a real benefit that truck operators are able to meet their stopping needs and the new federal stopping distance requirements without having to make significant changes to their drum brake specifications or service practices," adds Joe Plomin, vice president, truck, ArvinMeritor. "We have the technology and products and we are ready to support our customers."

Bendix brand foundation brakes also meet the new NHTSA mandate. "Bendix foundation brakes offer the fleets and the OEMs solutions in full drum brake, full disc brake, and combinations of air drum and disc brakes, based on their requirements, says Douglas King, marketing manager, Bendix Spicer Foundation Brake. "The  company's drum brake solutions won't require extensive modification in fleet operations, service or training."

He points out, "Years prior to it becoming final, developing a range of solutions and technologies to address the stopping distance regulation has been one of our engineering priorities. Many OEMs require foundation brake solutions capable of exceeding the mandated requirements, thus allowing all of their vehicle configurations to go beyond the 30% directive for shorter, straighter stopping."

In some cases, but not all, larger drum brakes may be required. "ArvinMeritor will continue to offer an array of brake sizes, including 15-in. steer axle packages," says Pennington. "This is particularly important for weight-sensitive customers. However, transitioning to larger brakes will provide some advantages, including increased lining volume to drive longer service intervals, lower operating temperatures, reduced fade and improved performance."

All wheel end air disc brakes are also an option. "You can generally generate more torque output with an air disc brake," says Aaron Schwass, foundation brakes product line director, Bendix Spicer Foundation Brake. "You can achieve the shortest pure stops with an all-wheel air disc brake solution."

According to King, air disc brakes can provide twice the life of drum brakes in the same vocation and duty cycle. In the long term, the air disc brake may have the better value proposition for most fleets.

Impact on OEMs
From the truck manufacturer's standpoint, few changes in current braking technology are anticipated.