Overdrive Magazine | Trucking Business News & Owner Operator Info
Issue link: https://read.dmtmag.com/i/580471
42 | Overdrive | October 2015 I n 2013, when new federal stopping distance regulations for heavy trucks became law, many in the industry thought that air disc brake adoption would accelerate rapidly. It hasn't happened. A big part of the resistance is cost. Spec'ing air discs for three tractor axles is more expensive than doing the same for drum brakes. But once they become more common in the United States, air disc brake prices are expected to drop, as was the case in Europe. The advantages of air disc brakes are that they are more efficient at meeting regulated stopping distance requirements, they weigh less, they require less maintenance than drum brakes, and their design makes them less vulnerable than drum brakes to violations. Air disc brakes are common in Europe, says Nicole Oreskovic, product manager of air disc brakes for Bendix. In North America, however, they traditionally have been considered a niche technology best suited for bus, fire truck and other specialty applications. At the height of their market domination prior to 2013, drum brakes in the heavy commercial truck market held a commanding 94 percent share. Air disc brakes made up the rest. Since 2013, some fleets opted to switch to air disc brakes to meet the new guidelines. Truck makers now offer more air disc products as both standard and optional equipment on new tractors. Air disc brakes now have about 10 percent market share in the United States, "with the front steer axle leading the way," says Bill Hicks, head of trailer product planning for SAF- Holland's suspension systems. "Today, air disc brakes continue to grow as an overall percentage of the market, with power units leading trailers," he says. National Highway Transportation Safety Administration regulations that became effective in 2013 require unloaded heavy trucks moving at 60 mph to stop in 235 feet instead of the prior regulation's standard of 335 feet. While the NHTSA regulation led to some acceptance of air disc brakes, design tweaks on drum brake systems have allowed them to deliver improved braking performance well within NHTSA's guidelines. And while air disc brakes offer significantly enhanced braking performance in all weather conditions, drum brake enhancements have made it easier for buyers to put off the more expensive technology. Drum brakes today feature larger chambers and 24-square-inch diaphragms with a long 3-inch stroke. This compares to a 20-square-inch diaphragm with a 2½-inch stroke on older brakes. Air disc brake systems continue to make Class 8 inroads, even as drum brakes improve. BY JACK ROBERTS The other brake option By using air disc brakes, maintenance downtime can be reduced because brake pads may last up to twice as long as drum linings. Air disc brake systems continue to make Class 8 inroads, even as drum brake option Air disc brake systems continue to brake option Air disc brake systems continue to SAF-Holland's Integral Air Disc Brake Axle System with P89 Wheel End Package is designed to be lighter than a comparable drum brake.