Shock absorbers can make a dramatic difference to how a vehicle handles. The basic purpose of a shock absorber is to control the movement of the suspension. To do that, one end of the shock absorber is connected to the moving suspension and the other end is bolted to the body or frame of the vehicle. One of these ends is connected to a shaft and piston assembly that moves up and down inside the shock absorber. Oil inside the shock absorber flows through orifices in the piston to slow the movement of the piston and thus the suspension. To control the flow, small control discs or flapper valves are used so that the shock absorber can compress quickly when you hit a bump but extend much slower to control any bounce in the suspension.

2017 Chevrolet ZR2

2014 Chevrolet Z28

Shock absorber tuning is done by changing the size of the orifices in the piston and the strength of springs that close the control discs. High performance shocks still use the same principles but may use pressurized gas inside the shock to prevent the oil from foaming as it passes through the orifices. There is another way to control oil flow and that is with spool valves, and for the 2016 Chevrolet Colorado ZR2, GM has gone one step further and introduced Position Sensitive Spool Valve technology.

Spool valve technology is not new but the ZR2 is the first mass-produced truck to include it. In 2002, spool valve shock technology was introduced for Champ Car racing. From 2010 to 2013, it was part of the winning Formula 1 Constructors Championship. These vehicles use hand built custom shock absorbers, as did the 2014 Camaro Z28. Now the 2016 Colorado ZR2 takes it one step further.

The ZR2 uses three spool valves to control oil flow. Why spool valves? They reduce fade compared to conventional shocks due to frequency and temperature variations and have a better response rate compared to disc valves. The refined shape of the spool valves and oil passages reduces oil foaming so less gas pressure is needed inside the shock absorber. The result is a more comfortable ride without any sacrifice in performance.

2017 ZR2 Multimatic shock absorber

2017 ZR2 Multimatic shock absorber

Trucks have special shock absorber requirements – especially high performance off-road trucks. Not only do they have to control the suspension over many small bumps, they also have to control the suspension as it travels over large holes and hills. The oil in the shock absorber heats up as it flows rapidly through the control valves and this changes the viscosity of the oil so the addition of a larger external reservoir helps keep the oil temperature down. With normal use on the road, only two valves are needed – one controls oil flow as the shock extends and the other controls oil flow as the shock compresses, but when off-road, the big bumps make the suspension move much more. The shock absorber movement gets closer to the end of its travel range and different damping rates are needed to control the suspension movement. This is where the third spool valve in the ZR2 dampers comes into play.

As the shock absorber extends, additional holes in the body of the shock are uncovered that direct oil to the third control valve. This valve now controls the damping over the big bumps. With three damping rates, the shock absorber works for both on and off-road adventures.

There is a Canadian side to this technology too. The shock absorbers and damping rates were developed at Multimatic Technical Center in Markham Ontario and Multimatic is the manufacturer of these shock absorbers designed for the Colorado ZR2.

About The Author

Jim Kerr

Driving and crewing for race teams at the drag strip, the stock car track and road race courses helps fuel Jim's enthusiasm but the real joy is experiencing our vast country on road trips around North America.

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