Air Disc Brakes – Can't Live With Them, Can't Live Without Them

How one fleet has made air disc brakes and S-cam brakes live together in peace and harmony

The additional weight of the air disc brake units hasn't been an issue for Szapacs, because the extra pounds are limited to the steer axle. "There is a slight penalty, but you can afford another 40 pounds up on the steer axle, because it's so hard to get 12,000 pounds on the steer axle," he explains. "You know, you get 11,600 to 11,800 pounds, so what is 40 pounds more? You have 11,840. If you doubled that and you had an extra 80 pounds on the tandem drives, yeah, you'd have an issue there."

The higher purchase price is also a non-issue. The first round of purchases in the 1980s was partially subsidized by the manufacturer, but now that the units have been part of the fleet's standard spec' for 20 years, the cost is all but invisible. Says Szapacs: "It's there, but it isn't."

Of course, the most important issue is performance, and on that score the air disc brakes have proven themselves over and over for two decades.

"With the product we haul, we really promote safety," says Szapacs. "We have an excellent safety group and an excellent safety record, and that's one of the reasons we went to the air disc brakes. We felt that the cam brakes were really outdated; they were developed right after they came out with pneumatic tires, I believe! I mean, they've been perfected, and they've really improved the performance of it, but the disc brake does afford a much shorter stopping distance."

Although Szapacs has never measured the improvement in stopping distances, his drivers can tell the difference between air disc brakes and S-cams. In fact, when the drivers were first getting used to the increased stopping power, they would run right up to offramps at full speed, because they knew they could stop safely in a shorter distance!

"We weren't expecting that," Szapacs admits. "But they got to rely on the system, they knew it would really work, you didn't have fade, so those were some of the results that maybe weren't most desirable. Our driver trainers worked with all the drivers, and now, especially with air disc brakes only on the steer axles, they do notice there is still a much shorter stopping distance than with cam brakes all the way around."

If there is any real glitch to the system, it is the availability of the spec'ed components and of replacement parts. There have been times when Szapacs has found himself reluctantly playing the role of the chicken in a "chicken-and-egg" situation. OEMs are reluctant to equip trucks with air disc brakes until there is adequate demand, but customers are reluctant to demand air disc brakes as long as they know that availability—and, thus, product support—is lacking (see sidebar, above). Those memories of the 1980s still linger, and there are few fleets willing to take a chance.

But Szapacs has never been reluctant to ask his truck suppliers to equip his units with air discs, and all of them—from White in the 1980s to Mack in the 1990s to Freightliner in the ‘00s—have come through, after some insistent nudging.

Parts, however, can be a different story.

"Believe it or not, we have had some instances where we've had problems getting brake pads, because we don't really use them," Szapacs admits. "Mack didn't put them in their parts inventory because we didn't request them, because if everything worked right, they'd run off the life of the vehicle.

"It sounds crazy, but that actually happened to us," he says. "We had a truck that got a stone wedged between the head and the caliper, and it damaged the rotor and the pad. This happened in Arizona, and we could get a rotor but we couldn't get a pad! We had some pads stocked at some of our locations, so we over-nighted some out. But we couldn't get them through the OE, because they didn't stock them; there was no need for them."

As other fleets wonder how they might meet the proposed DOT/NHTSA stopping distance standards, Air Products is already looking ahead to the next generation of air disc brakes. To avoid 2007 engines, Szapacs is virtually doubling his normal new truck orders (from 80 to around 150) both this year and next, and he wants to make sure that next year's order includes the next generation of air disc brakes.

How will you stop your trucks with a 30 percent shorter stopping distance? If you follow the lead of Ron Szapacs, you may surprise yourself one day, when you realize you "can't live without" air disc brakes.

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