Take a Lap! By: Larry Edsall © PickupTruck.com, 2003 Posted: 02-22-04 23:35 “Are you sure you want to do this?” asks the voice coming from inside the full-face racing helmet that covered the driver’s head. The driver is Tom Wallace, who on his rare free weekends, races a tube-frame, carbon-bodied, 750-horsepower GT1-class Chevrolet Camaro. Wallace also was part of the engineering team that made history in the mid-1980s by building the Buick GNX, a rear-drive, turbo V6-powered car that became one of the fastest production cars of that decade. For the next few laps, Wallace will wring out another rear-drive Chevy, although this one can switch to four-wheel-drive at the turn of a knob. This one also has four doors plus an open bed behind the passenger compartment and, for good measure, will tow 4000 pounds. This is a 2004 Chevrolet Colorado, equipped with the ZQ8 “sport” suspension package. Wallace is vehicle line executive for General Motors’ mid-size trucks, and one of his roles is to push those trucks to – o.k., often beyond – their limits. Apparently it’s rare that anyone volunteers to ride along. But I’ve chosen to do so because I know Wallace will get every foot-pound of performance out of this truck, will test the adhesion of its tires beyond the point where I’d be comfortable driving, and I want to experience just what this truck and suspension can do. I already have a pretty good idea, if not of the absolute limits, then at least of dynamics that only a handful of paying customers are likely to exceed. I’ve just driven the Colorado on paved public roads that twist into the Superstition Mountains east of Phoenix, and now we’ve come to GM’s Desert Proving Grounds in the flat desert landscape in Mesa to do laps around the vehicle dynamics road course in this truck and its competitors. By the way, none of those competitors are trucks. There’s not a Ranger or Dakota, a Frontier or Tacoma in sight. Instead, the competitive set for this test includes a Pontiac Vibe GT, a turbocharged Chrysler PT Cruiser GT and a Ford Mustang V6. Wallace had provided lively conversation over the dinner table a couple of nights earlier – and we’ll return to the subject of a Colorado SS in a few moments – but now, before he has to fly back to Detroit for yet another of those meetings that keep him away from the race track, we’ve asked him to show us the wild way around the course. Which he does, see-sawing the steering wheel to keep the truck pointed toward the next apex while the tires squeal loudly as they struggle to relay to the pavement the inputs from Wallace’s right foot. It’s a losing battle. The Continental TouringContact AS tires were carefully chosen for this truck, but street tires of 235/50 aspect are not going to provide optimum traction in the face of driving as aggressive as Wallace’s is on the track today. But with the volumes at which this Colorado sells – nearly 20 percent of Chevy’s all-new-for-’04 midsize pickup will be equipped with the ZQ8 suspension – performance engineer Joe Taverna had to take a more reasoned approach as he was tuning all of the suspension packages for GMT 355. GMT 355 is the internal codename for the truck sold as the Chevrolet Colorado and GMC Canyon. They are available in three body styles – regular, extended and crew cab – in two- and four-wheel drive and with the standard, heavy-duty Z85 suspension, a Z71 off-road package or the Chevy-exclusive ZQ8 “sport” version. Initial dynamic targets for the ZQ8 were the old Chevy S-10 Extreme pickup, and when that standard was passed almost immediately, the Chevy Camaro Z28 was the next handling benchmark. Next, Taverna took aim at the Vibe GT and suddenly we’re looking not so much at a compact truck as we are at a sport compact. Imagine, fast and furious, and with a couple of jet skis or dirt bikes in tow. But we’re still looking at a compact truck that has to be able to do some serious work; and as Wallace will tell you, there’s not nearly as much play time as we’d like to think. Still, Taverna found a way to make the Colorados that ride on the ZQ8 setup as sporty as possible, at least for a truck that will sell in significant volumes. And in the process he caused a change that enhances the ride quality of every GMT 355. After preliminary suspension development work, Taverna realized that to get what he wanted, what he needed out of the ZQ8, he’d need to change the body mounts, an expensive and complicated procedure, too expensive and complicated to meet volume and pricing targets. But because changing body mounts would provide across-the-range ride improvements, the decision was made to equip all GMT 355s with urethane mounts. Though it may seem counter-intuitive when it comes to a higher-performance modification, the new mounts are actually softer, thus providing better impact isolation and making course roads seem almost smooth. “The softer compound was chosen to improve coarse road and impact isolation,” Taverna explains. But because the frame for the new truck is some 250 percent stiffer than the one used beneath the venerable S-10 and Sonoma, the new mounts also opened what Taverna calls “a library” of opportunities to fine-tune the suspension. How’s it feel? Well, there’s a spot in the road on the way to the proving grounds that has a pair of potholes worthy of the Detroit freeway system and the Colorado stayed amazingly calm through them. But on the handling circuit, even with Wallace driving, the truck was able to keep its composure. Pretty much. How’s that happen? Basically, it’s a carefully crafted soft spring-firm shock setup. Taverna worked to achieve aggressive handling performance without significantly sacrificing ride comfort, he explains: “The front springs actually have a linear rate, but the jounce bumpers were tuned to progressively add to the rate. Similarly in the rear, the second stage leaf was tuned to progressively add to the rate (primarily for load-carrying capability). But, the ride rates at curb position were intentionally kept low for ride comfort. Then, the shocks were valved to provide higher damping forces and enhanced handling performance.” There’s also a rear stabilizer bar, revised steering gear with a quicker ratio and 17-inch wheels with those Continental TouringContact AS tires, and ride height has been lowered by more than an inch. Factoring in the new wheels and tires, compared to the standard setup, the front end of the ZQ8-equipped Colorado has 3.5 inches less ground clearance and the back end is 1.1 inches lower. Except for the fact that you’re still sitting much higher in the truck than in the Mustang, the Colorado not only holds its own against the pony car, but GM says that in its internal testing, the Colorado with ZQ8 was faster around the circuit than the six-cylinder Mustang. It also beat the GT Cruiser, and was within two-tenths of a second of the turbocharged Vibe. The Colorado is available with either a 2.8-liter four-cylinder engine that produces 175 horsepower and 185 pound-feet of torque, or a 3.5-liter inline five (both are based on the inline six from the TrailBlazer/Envoy) that makes 220 horsepower and 225 pound-feet of torque. The rear tires seem to keep up just fine with the four-cylinder engine as we whip it around the test track, but they struggle in vain to put down all of the five-cylinder engine’s power as we try to storm around fast, sweepers. On the public roads in the mountains, the ZQ8 firms up nicely, providing both good feedback and control as we push the truck through the curves. Yet the ride is sedan smooth when we cruise around town or on the expressway. It probably would take only a little aftermarket tuning for the Colorado to exceed all of its competitors. Taverna agrees that for those who really want to optimize performance, the truck could be lowered a couple more inches and there’s room for wider and grippier rubber beneath the wheel wells. You could do-it-yourself now, or we get the strong impression from Wallace that if we wait a year or so, there may be an SS version of the Colorado available at your nearby Chevy store. It sounds as if one of those things keeping Wallace away from the racetrack is work to make a business case for a Colorado SS, a limited-production sport compact (truck) that would appeal to more hardcore enthusiasts. While some old-timers might think you can put the SS badge only on vehicles with V8 engines, there may be others who are younger at heart, who just might accept an inline five cylinder – as long as it produces 300 or more horsepower, which Wallace says is possible with either a turbo or supercharger. Add in larger brakes, racing-style seats, maybe a special shifter for the gearbox -- and even an audio system with a watt rating that equals the engine’s horsepower numbers -- and such a vehicle still could come to market for around 30 grand. And if Tom Wallace needs a passenger to ride along when he wrings that one out, we know where he can find an eager volunteer.