Bendix introduced its ADB22X® air disc brake to the North American commercial vehicle market back in 2005, and every year since, adoption of air disc brakes (ADBs) has grown. In fact, more than one third of new North American Class 6-8 air-braked wheel-ends now come equipped with air disc brakes. That percentage is only expected to keep growing as fleets and owner-operators alike experience their advantages on and off the road.
Where trailers are concerned, though, ADBs occupy a smaller portion of the market – although this number continues to grow as well. For many fleets, spec’ing brakes on the trailer may be somewhat of an afterthought. But what difference would it make to choose air disc brakes for trailers?
Reasons to Equip Trailers with ADBs
For starters, there are the same reasons you’d select them on your tractor: shorter stopping distances, straighter, stable stops; virtually no brake fade; and quicker pad replacement. ADBs have an internal adjustment mechanism that can help fleets and drivers avoid out-of-adjustment penalties during roadside inspections. The design of ADBs prevents water from collecting in them – which can be a problem for drum braked vehicles that are parked for long periods of time – reducing the chance of corrosion and related problems like rustjacking.
Additionally, if you already spec air disc brakes on your tractor(s), equipping your trailers with ADBs can mean streamlined inventory and maintenance practices. The Bendix® ADB22X-LT®, for instance, was engineered specifically for trailers, but uses the same wearable parts and pads as the standard ADB22X.
Stopping Distance and Safety
Air disc brakes on any axle make a difference in stopping power: From 70 mph (112 kph), an 80,000-pound tractor-trailer combo with Bendix ADBs on the steer axle alone stops 20 feet (6 meters) shorter than an all-drum combination. Add ADBs on the entire tractor, and stopping distance is further reduced by 40 feet (12 meters). Put them on the trailer as well, and you’re talking a 50-foot difference (15 meters). The performance advantages of ADBs also mean they provide better support to today’s more advanced driver assistance systems (ADAS), which can activate brakes at individual wheel-ends as part of systems offering full-stability and collision mitigation.
It’s important to note that trailer brakes can face unique usage challenges: If a driver regularly chooses to use the trailer brakes as the sole or dominant stopping force of the vehicle, it can present an opportunity for them to generate more energy than the wheel-end was designed for. Bendix designed the ADB22X®-LT with this and other factors in mind so that the brake will perform at the proper and safe levels for trailers.
Dolly Talk
It’s a straightforward proposition to introduce disc brakes to a fleet through most standard tractor-trailer combinations, and it generally makes no difference whether you begin with ADBs on a tractor or trailer. But if you’re hooking up doubles or triples in a multiple-trailer combination, Bendix recommends using ADB-equipped dollies only in combination with other disc-braked equipment.
Our testing has shown that on an all-drum-braked tractor and double trailer, equipping the connecting dolly between the trailers with air disc brakes will likely lead to accelerated pad wear on those brakes. As they take on the extra work when the drum brakes fade, the ADBs on that dolly will see an increase in temperature and accelerated pad wear.
We know you’re weighing a lot of options when it comes to braking solutions and total cost of ownership. Equipping trailers with ADBs can help you solve that equation while delivering benefits on and off the road. Want to see what you might save by spec’ing ADBs over drum brakes? Check out ValueByBendix.com, an easy-to-use value calculator that generates a customized report with potential savings based on your inputs.
And the Bendix team is always happy to answer your questions. Give us a call at 1-800-AIR-BRAKE (1-800-247-2725).
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