Each trailer in the United States and Canada is required to meet baseline performance requirements for air-braked trailers. And each trailer requires a different valve setup for optimum performance.
Bendix offers these tips for making sure the valve setup is correct for the trailer's length, vocation and features, taking the trailer from just compliant to ready for the road.
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"Regulations set the starting point, but trailers need different valve setups depending on their design," says Robin Humphreys, manager of trailer products for Bendix. "A short dry van might use a basic system, while longer or towing trailers usually need a booster valve to keep brakes in sync and meet the regulatory timing requirements. And as trailers get more axles or carry tougher loads, additional valves help keep braking balanced and predictable."
The correct trailer braking system ensures consistent stopping distance, predictable handling and readiness for stability features and connectivity, Bendix says.
A basic two-wheel-speed sensor with one modulator ABS configuration will satisfy government requirements for over-the-road dry vans, Bendix says.
Longer trailers may require a control-line booster valve to help meet timing expectations. Wide-axle-spread trailers may require extra valving to serve the brake layout and vocational trailers that carry higher-risk loads may need four sensors and two modulators. Trailers designed to tow should be engineered with a booster valve to meet the regulations' timing requirements.
Trailer roll stability programs require accurate trailer inputs, Bendix says, to tailor software and interventions. Planning stability at the design stage makes sure the sensor and modulator placements, plumbing and valve selection all work together.
"Trailers with more axles or specialty designs benefit from extra valves and more points of control," says John Ripley, vehicle systems engineer at Bendix. "Added control helps trailers respond more smoothly in real-world maneuvers and also sets the stage for easier diagnostics, stability features and the connectivity fleets are looking for."
Bendix also says features such as lift axles, rear unloading systems, friction and rotor-wear alerts, or low-system-pressure warnings can drive which valves and electronic control units are built into the trailer by manufacturers and their suppliers.
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Fleets are also asking for trailers that share data with service teams, and those expectations, too, can shape electronic control unit choice, Bendix says. The right unit enables contemporary diagnostic functions while also positioning the trailer for future capabilities such as predictive maintenance alerts, tractor-trailer communication and advanced stability functions.
"Thinking about connectivity up front helps fleets avoid costly retrofits later," Humphreys says. "Advanced controllers open the door to diagnostics, service tools and the electronic features that may keep trailers competitive in the years ahead."
Diagnostic tools should be kept up to date, Bendix warns, as well as technician training to maintain optimal performance.
"The right valve choices begin with fleets clearly defining their operating needs," Ripley says. "When fleets, builders and brake-system suppliers align early at the system level, it's more likely to result in a trailer that delivers on both compliance and performance."
Bendix offers these spec decisions to consider to ensure the design supports both compliance and performance:
- Trailer basics: Length, wheelbase, axle count and spread, and towing capability.
- Braking setup: ABS/stability system type.
- Valve needs: Booster or relay valve for longer/towing trailers.
- Feature set: Lift axle control, rear unloading, friction and rotor-wear alerts, low system-pressure warnings.
- Connectivity: Diagnostics/data-sharing for current and future smart-trailer needs.
- Testing: End-of-line checks and documentation, including timing, sensor placement and plumbing.
