Test Drive
To demonstrate both its stability control system and the effectiveness of its ADB 225 air disc brake, Bendix put together a traveling roadshow, which the trucking press was invited to attend. On hand was a Kenworth T2000 with ADBs and a test flatbed carrying a representative-height test load. Most importantly, it had test outriggers — training wheels — to restrain the trailer.
For the stability demonstration, two courses were set up: a so-called J-turn, which is a straight line leading into a reducing radius left turn; the other was a lane-change avoidance maneuver where the truck aggressively avoids an in-lane obstacle, then quickly returns to its lane. This double lane change results in a crack-the-whip on the trailer that can very easily cause a rollover.
As we've seen from stability demos before, with the system inactive, the truck very quickly becomes unstable, the trailer picks up inside wheels and — were it not for the outriggers — would roll over. With the system enabled, brakes come on with ABS pulsing and the trailer wheels stay firmly on the ground. The difference with Bendix ESP was the pulsing of the front wheels, which could clearly be identified by the excursions of the front axle as the brakes applied and released.
CDL holders in the press were invited to drive the trucks through these maneuvers — a measure of Bendix' confidence in its system.
The J-turn was not especially daunting, though the first run through at rollover speeds brought me the usual sweaty-palmed response going into the curve. Once the ESP intervened though, I found subsequent runs through the turn were easily completed, keeping a tight line on the cones and letting the brakes safely reduce speed while steer axle braking kept the Kenworth's nose tucked in to the line I wanted.
The lane change was a real eye-opener, first because we seemed to be approaching the obstacle at a speed much to fast to even get around it and still keep within the cones — even without worrying about a rollover incident. As before, as the outfit started to get out of shape, braking pulled down the speed — but it was the steering control that was the most impressive. Regardless of what was happening at the rear of the trailer, the tractor kept pointing in precisely the direction I wanted it to go and we cleared the obstacle without touching any of the cones. Sure, I could feel the front end pushing, but the selective braking kept it reigned in tightly.
In both maneuvers, the braking reduced road speed to well below optimal and we were thankful to have the Meritor FreedomLine automated transmission to pick up the right gear to get back up to speed. Any driver with a manual shift would be suitably chagrined to have to dig around in the transmission to find a suitable gear to get going again.
Was the lane change the most impressive maneuver of the day? Most certainly. But a close second was taking a fully air-disc-braked tractor/trailer around the circuit to build up to a speed of 68 mph into the braking area. It was a simple foot on the clutch, slam-on-the-brakes ABS stop. Except the truck stopped like a sports car. Moreover, second time around, I did it taking my hands off the wheel and it stopped in a dead straight line, in-lane.
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