Heavy Duty Trucking

JUL 2014

The Fleet Business Authority

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www.truckinginfo.com Yet here we are, a year after the final rules change became effective and more than three decades since they first appeared in North America, and disc brakes still comprise a small minority of air brakes being bought by truck operators. Put another way, 90% of heavy truck buyers today still choose tried- and-true drum brakes, according to manufacturers we talked with. These are not good ol' drum brakes, but improved designs that stop better and last longer than past products. They have to perform better to meet Federal Motor Vehicle Safety Standard 121's shorter limits, and to do so many of them are larger. That, in turn, allows their linings to stay in service for more miles, supplier reps say. "Air disc brakes cost more, so there isn't a more cost-effective way to stop a truck than a drum brake," says Joe Kay, director of engineering for brake systems at Meritor, which offers both brake life," Ganaway says. With drums, "they get hot and wear rates increase exponentially." It's easier and quicker to change a set of pads on disc brakes than shoes on drums, Kay and Ganaway both note. Pads take as little as 15 minutes to change out compared to almost an hour for a set of shoes. That's where the maintenance payback can come into play. But the advantage is less if original linings on a drum-brake system can be made to last a long time, which is possible with larger brakes. To meet 121 stopping requirements, steer axle brakes have gone from 15x4 inches to 16½x5 inches, while drive-axle brakes stayed with 16½x7s, Ganaway explains. Daimler Trucks chose to make 16½x8-5/8-inch drum brakes standard on drive axles for Freightlin- ers and Western Stars. However, there is a movement to air disc brakes and it's accelerat- ing. "We announced the sale of our half a millionth air disc brake at the Louisville truck show, which was only two years after we announced the first 250,000th" following introduc- tion of current models in 2005, says Bendix Spicer's Ganaway. "Fleets are paying more attention to foundation brakes and began experimenting with air disc brakes. They are becoming more and more comfortable and are coming back for more." "Air disc brakes are progressively increasing," says Steve Hansen, direc- tor of sales and marketing at Wabco, which sells discs. "There are two lev- els of fleets: those looking for brake performance — like tankers and heavy steel haulers — and those who want a longer lifetime. With discs you don't have to touch the brakes as often." Adoption percentages vary: types. He means on tractors, which the "121" rules affected, and for which drum brakes were specifically improved. But discs can stop those same tractors quicker, which is why some fleets are adopting them. And discs hold up better in severe-service applications, like trash collection trucks, many of whose operators have embraced them. "There's an added expense with disc brakes and operators need time to get a proper payback," says Gary Ganaway, director of marketing and global customer solutions at Bendix Spicer Foundation Brake, which also offers both drums and discs. Cost for air disc brakes varies by truck builder: At Kenworth and Peterbilt they're standard on the steer axle. For all the other builders the cost of upgrading is $800 to $1,000 per axle. In some cases there can be a payback through maintenance. With discs, "refuse trucks doubled their Kenworth and sister company Peterbilt are standard with air disc brakes on steer axles and use drums on rear axles, though this KW T880 heavy-haul tractor has discs on the tandem, too. Other builders have made discs optional. Brake Trends

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