The minimum you need to play off-road. The huge tires on Chevy's new S-10 pickup with the optional ZR2 off-road package tell you the truck is meant for serious dirt driving. Size is critical to mud-loving off-roaders, and the minimal gear is the 31-inch-diameter, 10.5-inch-wide “light-truck all-terrain” tire, four of which are standard issue on the ZR2. These tires are about 1.5 inches larger in diameter than most of the off-road tires available on mid-sized pickups and sport-utilities.
“The 31-by-10.5 is just about right when it comes to a tire for all possibilities,” one off-road fan and Chrysler engineer told us. Tires this size are better than the smaller stock ones because they offer more flotation on soft surfaces, greater puncture resistance due to thicker sidewalls, and increased ground clearance from the larger diameter.
There are drawbacks to this size: Larger tires have a higher rolling resistance, which reduces fuel economy. And the bigger tires weigh more (a substantial dozen additional pounds of critical unsprung mass per tire)—sometimes more than stock shock absorbers can manage over bumps. So just adding big tires alone can give an off-road truck a boingy ride.
View Price on AmazonBig tires always lead to compromises in pavement handling, and they make more noise, say GM truck engineer Frank Taverna. Plus, the 31-by-10.5s just won't fit in the fender wells of some vehicles.
To overcome the big-tire disadvantages, the GM truck folks spent a lot of money to redesign the front-end pieces of the new S-10, so it can accommodate those big tires properly. News accounts say GM spent $30 million to produce this ZR2 package. Most of that went for a new front subframe with relocated control-arm mounting points. The new frame raises the ZR2 two inches and maintains wheel travel and suspension geometry. This frame is different from what comes on the other six available chassis (three rear-drivers and three four-wheelers) in the GM small-pickup lineup.
The ZR2 also gets enormous Bilstein shock absorbers, nearly two inches in diameter (almost double the size of stock shocks), and four-inch-wide fender flares to keep mud from splashing up on the windshield. The ZR2 cruises quieter and with less drama on the highway than any 31-by-10.5-equipped truck we've driven. The chassis feels stiffer, and the behavior of the truck on bumps is more calm and predictable. More progressive leaf springs and a Panhard rod—unusual for a truck—keep the rear end of an unloaded ZR2 from bouncing around too much.
The tires were specially developed with BFGoodrich to have a round shoulder, and hence to leave a longer footprint. This keeps the steering from feeling too vague on-center, says Taverna. It works. Although the ZR2 is louder and harsher than the car-tire versions of the new GM small pickup, it is not as raucous a ride as, for example, a Ranger with off-road tires. The ZR2 rides with impressive isolation but feels more connected to the road than Chevy's bigger C/K pickups.
The ZR2 is available with either a 165-hp or a 195-hp 4.3-liter V-6. Get the 195-horse motor. It pulls the truck away from stop smoothly but without much of a rush. Getting to 60 mph takes 9.1 seconds, slightly better than average for mid-size pickups we've tested. The GM V-6 is relatively efficient, and the ZR2 gets a 17-mpg EPA city fuel-economy rating, 1 mpg better than the 160-hp V-6 Ford Ranger.
Source: caranddriver.com
