Learn more about the Colorado ZR2's most noteworthy feature
The Chevrolet Colorado ZR2 is equipped with a laundry list of specialty off-road hardware designed to make the truck unstoppable in any terrain. Among its locking front and rear axles, body-protecting rock sliders, and other specialty equipment, there’s plenty to highlight, but today we’re going to focus on its most noteworthy feature: Multimatic Dynamic Suspensions Spool Valve (DSSV) shock absorbers.
If you’ve ever flopped down on a bed, you know springs don’t just compress and expand once. They’ll keep bouncing up and down until all the energy of your flop is dissipated. The same thing would happen to your vehicle were it not for shock absorbers. To keep the body from bouncing all over the place—up and down, side to side, front to back—shock absorbers soak up the extra energy so the suspension only moves enough to dampen the impact and allow the wheel to move over or down into the obstacle in a controlled manner.
Shock absorbers work by moving a piston through oil inside a sealed tube. As the piston moves, the oil is typically forced through holes in the piston head, slowing down the movement of the piston. Exactly how fast the oil flows past the piston is usually controlled by metal discs, which bend and deflect to allow the oil past. How much and how quickly they bend determines how much damping effect you get. Even the best discs, though, aren’t super precise. Manufacturing tolerances can allow as much as 15 percent deviation from the ideal oil flow rate.
Multimatic’s DSSV shocks work differently. Rather than discs acting as valves, DSSVs use an additional set of little spring-loaded pistons in special sleeves, which they call spool valves. Holes laser-drilled in the sleeves allow the oil through as the little pistons move. The size, shape, spacing, and number of holes all determine how quickly the oil can move, giving manufacturers much more precise control over how the shock absorber behaves.
In the case of the ZR2, the DSSV shocks have been modified to put the spool valves in a separate chamber on the side of the shock absorbers rather than inside the main tube. Moving them outside the main tube allows for greater shock travel—and thus greater suspension travel—and improves cooling. Heat is a very serious issue for shocks off-road when they’re constantly making big movements. A third spool valve, mounted on the main piston, only sees action when the suspension movements are really big, and it’s tuned to bottom and top out like the suspension on a Baja race truck.
By using Multimatic’s DSSV shocks, engineers were able to give the ZR2 more suspension travel than they might have with traditional shocks, better cooling for high-speed off-roading, and better control over each wheel’s movements as the truck climbs rocks, drops into holes, and speeds over washboards. Separate, specialized spool valves allowed Chevrolet to optimize on-road and off-road ride quality and control separately to give the ZR2 a broader performance envelope than it would otherwise be capable of.