No Poseurs along the Back Roads; we take GM's new small trucks on a true off-road adventure.(News)(Product/Service Evaluation)

Byline: LARRY EDSALL

With few exceptions, an invitation from an automaker to "come drive our newest 4x4'' usually trans-lates into a cruise along some gravel road, with perhaps a quick detour to climb a hill steep and rocky enough that you might actually engage four-wheel drive, then crest the hill's summit and ease on down the other side.

So we were skeptical when General Motors said it had set up a daylong off-road exercise to show the abilities of its new Chevrolet Colorado and GMC Canyon midsize pickup trucks (Oct. 6).

Our skepticism waned soon after we punched the 4HI button only a few miles into the Telegraph Canyon Trail, evaporated as we carefully rock-climbed along the Martinez Mountain Trail, and turned to awe in Box Canyon, a steep-walled slit through the mountains some 60 miles southeast of downtown Phoenix.

Backcountry Adventures: Arizona (reviewed in AW, Nov. 26, 2001) rates the Martinez mine route a 4 and the Telegraph Trail and Box Canyon each a 5 on a scale that says 6-rated trails "are for experienced four-wheel drivers only,'' and are "potentially dangerous.'' Not that a 4 or 5 is a simple matter. Backcountry suggests that while a "stock SUV'' might suffice for a 4, for a 5 you'll need a high-clearance 4wd vehicle and even then some sections "may be impassable for inexperienced drivers.''

Indeed, there were several places where drivers needed a spotter's hand signals to assure proper tire placement for traversing boulders that blocked the way.

The 4wd trucks we drove were stock GMT 355s, and each was equipped with the new 200-hp Vortec 3500 inline five-cylinder engine and the Z71 ...