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MEDIUM-DUTY BRAKES

Posted: August 1, 2014

International Truck and Engine says a new hydraulic brake system with anti-lock brakes is now standard on International RXT, 3200, 4200 4×4 and 4000 series 4×2 models (with the exception of the mid-cab tractor). Called ‘Full Power’ and made by Meritor WABCO, it delivers optimized braking performance and reduced stopping distances.

Previous brake options used pressure from the power steering system to boost the master cylinder pressure output. With this new standard feature, electric pumps are used to generate hydraulic pressure. Stored pressure in the accumulators allows the full power system to build
pressure at the brake calipers significantly faster than the previous system. This faster response delivers “best in class” stopping capability, says International, with reduced stopping distances. With this release, International is delivering the first electronic brake-force distribution (EBD) system as a standard feature. EBD proportions brake force relative to axle-load conditions, providing balanced braking under varying load conditions.

The pedal feel is more responsive as the system has stored energy to provide an almost immediate response when applying the brake pedal.

The master cylinder acts only to send signal pressure to a control valve. In response to this signal pressure, fluid from the accumulators is sent to the brake calipers for stopping the vehicle. As a result, the master cylinder does not have to stroke as far, resulting in the better pedal feel. Less overall stroke allows for repositioning of the pedal, the company says, so it isn’t as high and is therefore set at a more comfortable height from an
ergonomic standpoint.

The system also provides two new optional features to customers — a powered parking brake and automatic traction control (ATC). ATC works at low-speed conditions to send brake pressure to wheels that are spinning to provide better traction. When both wheels are spinning at low
speeds, ATC commands the engine to provide the appropriate level of power while sending braking pressure to the spinning wheels. When sensors detect spinning wheels above 50 km/h, the ATC begins initiating “engine management”, which backs off engine power and does not apply braking pressure.

Powered parking will be available as an option and will utilize the Spring-Apply Air-Release (SAAR) parking-brake chamber. This chamber includes stoke indication, which identifies any damage or out-of-adjustment conditions with the parking brake. A service park brake indicator lamp on the dash will be lit should any such out-of-adjustment conditions be identified. The holding capability of this parking system is so strong that it’s impossible to drive through the parking brake when it’s applied, International says.

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