More trailers to benefit from disc brakes, ESC

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LOUISVILLE, KY – Air disc brakes appear to be gaining ground on drum-based designs, and they have a role to play in emerging automation options like platooning trucks, according to Bendix officials.

Last year, air discs were found on 16% of trucks and 6% of trailers — but that could reach 27% of trucks and 20% of trailers as soon as 2020, said Keith McComsey, director, marketing and customer solutions – wheel ends, during a briefing at the Mid-America Trucking Show.

Selected manufacturers have already begun to install the brakes on steer axles to help meet mandated 250-foot stopping distances, and the option is available on other wheel ends for those who want to stop in even-tighter spaces. Platooning vehicles that travel in tight packs would certainly increase the importance of quick brake response.

Using disc brakes on a steer axle and drums on drive axles will help to reduce a typical tractor-trailer’s stopping distances to 215 feet when rolling along at 95 kilometers per hour, McComsey said. Use them on all wheel ends and the stopping distances drop to 200 feet.

The benefits of discs are not limited to stopping power alone. They also better resist fade, the friction material lasts 1.5 times longer, and pads can be changed in minutes, McComsey said. Savings related to improved safety and fewer CSA violations pile on top of that.

“The value proposition on air disc brakes is really good,” said Fred Andersky, director, customer solutions and marketing – controls. “You can do a disc pad change in 15 minutes once you have the tire off. On a drum it can take an hour.” Systems that once cost as much as US $1,500 per axle can now cost about half that.

While much can be gained with the wheel ends on trucks, Bendix also cites further benefits realized on trailers.

 “It helps keep the trailer behind the tractor, which is where you want it,” McComsey said. When coupled to a disc-equipped tractor, a trailer with air disc brakes will shorten stopping distances by about 1.5 car lengths at 95 kilometers per hour. At 110 kilometers per hour the difference rises to 3.5 car lengths.

“At 50 feet, that can be the difference between a crash and a close call,” said Andersky.

It is not the only way braking systems can be improved, of course. Andersky stresses the value of oil coalescing filters and intelligent air dryers to support the air systems that now supply Automated Manual Transmissions as well as the brakes themselves. Kenworth and Peterbilt already offer them as standard equipment on their Class 6-8 trucks.

“When you brake hard, you don’t want that trailer doing something you don’t expect it to do,” he says.

Vehicle motion will be further enhanced this year with a mandate for Electronic Stability Controls on Class 7 and 8 tractors with Gross Vehicle Weight Ratings of more than 26,000 pounds. But many fleets have already realized the equipment’s value. Bendix has produced 500,000 Electronic Stability Control systems so far.

Looking further into the future, Andersky projected that the connections between tractors and trailers might require another form of support — in the form of a new electrical link or wireless Local Area Network to support autonomous vehicle technologies. He prefers the idea of a new electrical link, because it is the most secure against dangers like hacking.

“The trailer is going to become an integral part of the whole vehicle,” Andersky said. “It’s not going to be the poor stepchild.”

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John G. Smith is Newcom Media's vice-president - editorial, and the editorial director of its trucking publications -- including Today's Trucking,, and Transport Routier. The award-winning journalist has covered the trucking industry since 1995.

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