One of the first things you realize after your first day on a racetrack is that OEM shocks aren’t going to cut it. If you’re driving in HPDE, you need something that’s suited for double duty: track and street use. If you’re building a car for wheel to wheel, you need something dialed in for racing.
To find out more about shocks, how they work and how to shop for them, we caught up with Wyatt A. Gilbert with Motion Control Suspension in Alpharetta, Ga. If you’ve been paying attention, you know MCS supplies the shocks fitted to NASA Prototypes and various NASA Spec Series.
“The first thing you’ve got to determine is the car’s intended purpose,” Gilbert said. “Are you building a suspension package for a street car that’s going to have some spirited use here and there? Or is this a dedicated track car? “Or perhaps, is it going to be a combination of the two?”
There are several components that make up a suspension system. When you think of a coil-over assembly, this typically consists of three components: a damper, a coil spring, and a top mount of some sort, which connects the damper and coil-over assembly to the chassis.
Modern dampers, no matter their construction, will have a mechanical or hydraulic device that manipulates oil flow to achieve various damping forces at various velocities. More often than not, modern dampers also will have a nitrogen charge, which helps keep the damper from cavitating. There are three mechanisms commonly used to control damping forces in most damper systems today: a shim stack, an orifice, and a needle valve.
“When we say shim stack, we’re talking about little stainless-steel discs that vary in diameter and overall height and their strength as well,” Gilbert said. “The orientation and the method in which you stack them is going to determine the valving. You could have 15 shim stacks or you could have five. You could have them in various diameters. You could have a Christmas tree-style stack, you could have staggered stack and, depending, of course, on the overall thickness of these shim stacks, their diameters and how they’re stacked and how much pressure is applied to them, will determine what your valving is like. It’s all about restricting oil flow through those shims.”
A needle valve is exactly what it sounds like, a mechanism that allows oil to flow through a needle port. As you turn the adjustment knob, it’s opening or closing a port, which works well, but only offers a finite range of adjustment.
An orifice manipulates the flow of oil through machined holes. The benefit of using an orifice is that it offers a broader range of adjustment in damping forces, and doesn’t fatigue — damping forces remain consistent. This eliminates the need for frequent service intervals and revalving if you make a spring-rate change. It also allows for easy setup, because your settings remain the same, even when the damper is nearing its next service interval.
Depending on your application, goals, and rules set, you can get a shock setup as simple or as sophisticated as you want. The more adjustments you have available to you, the more opportunity you have to find grip. With that said, you also have more opportunities to negatively impact the car’s performance. When choosing a damper system, it’s critical to have ample support from your vendor and manufacturer. They should be there to support you in using the product to its full potential.
Motion Control Suspension offers single-, double-, and triple-adjustable damper systems in nonremote and remote-reservoir packages. The benefit of a remote reservoir system is packaging. By introducing a remote reservoir and hose, oil capacity and nitrogen cavities increase in volume, allowing for better heat dissipation and control. The added packaging space allows for more mechanical and hydraulic components to be used, increasing the number of adjustments without decreasing critical damper stroke.
Damping forces are measured in velocity and force. In the US, we measure damping velocities in inches per second and forces in pounds. These figures are measured on a damper dyno and plotted on a graph. The most common graph used is force vs. displacement. There are four sections in two groups. The two groups are compression and rebound forces, and these are split into two sections, low-speed and high-speed forces.
Choosing the right shock is about goals and it’s important to seek good advice. Motion Control Suspension takes calls from drivers all over the world. To get the right suspension package, you need to identify the car and its intended use, its weight, springs, downforce, if any, budget, class, tire size and compound, and then you can shop for the right combination of components.
“In its simplest form, you’re simply controlling oil flow. That’s all it is,” Gilbert said, adding that it’s key for maintaining the contact patch at each corner. “You’ve got a mechanism that’s going to control the rate in which oil is going to flow through something, which is going to give you your valving, and the purpose of controlling that flow is to control each corner independently to provide the most grip possible.”
RESOURCES
www.motioncontrolsuspension.com
