Ask any race-car builder to list the objectives behind the design of a great-handling chassis, and one of the key elements will be the ability of the chassis to keep as much of the tire footprint on the road as possible. An automobile, no matter how sophisticated, depends on four patches of rubber planted on the surface of the track or roadway to determine its traction limitations.
Many parts contribute to this end goal. Among them are springs, torsion bars, A-arms, and an engineered assortment of suspension components. Of all these pieces, none is more effective in controlling handling than the shock absorber. It's a control device that works with major suspension pieces to provide a stable yet adjustable method of damping or governing two types of mass: sprung and unsprung weight. The role of the shock absorber becomes more apparent when the automobile is a sports car.
This brings us to the subject at hand: the Chevrolet Corvette. Since its inception in 1953, the Corvette has played a pivotal role in the advancement of the performance scene in America. It is America's sports car, and those who drive it want performance. Any product offered in the marketplace claiming to enhance performance had better be capable of providing improvement.
Edelbrock Corporation, a leader in the manufacture of high-performance manifolds, aluminum cylinder heads, and a staggering inventory of racing products, has expanded into suspension systems, including shock absorbers. Although Edelbrock engineers shocks for several applications, this story will concentrate on those available for the Corvette.
What makes the Edelbrock shock different? Something called IAS, Inertia Active System. A simple fact should be noted. All shock absorbers are a compromise, and Edelbrock shocks reduce the compromise. To get a better understanding of the product, we asked David Shirley of the Edelbrock shock division to offer some theory behind the shock-development program.
"Designing a shock absorber requires making a compromise," he says. "The compromise is in the damping rates selected or 'stiffness' of the shock. A damping rate may be selected to provide good chassis control, which is characterized as a slow roll rate, minimum pitch angle during aggressive braking, and reduced heave motion over road undulations. Shocks with enough damping to provide nice, crisp handling and good chassis control are typically called performance shocks because they bias the ride characteristics toward performance, not ride quality. The compromise is, the shock with enough damping to control the chassis well is not the best shock to have when the vehicle hits bumps, dips, or other road irregularities that excite the wheels.
"The shock stiffness required to control the heavy, slow-moving chassis (the sprung mass) is not the best stiffness required to control the faster-moving, relatively lighter wheels and tires (the unsprung mass). Shock designers and tuners spend many hours shaping the force versus velocity curve of the shock in hopes of minimizing the compromise. In the end, however, all shocks produce the same damping force at any given speed whether the wheel extends the shock or the chassis extends it. The Edelbrock shock design minimizes the effects of this compromise with the Inertia Active System technology."
What Is Inertia Active System Technology?The Ricor Inertia Active System allows the shock to select from two distinctly different rebound damping rates or, more specifically, two different force versus velocity curves depending on the damping needs at any given moment-firm for chassis control or soft for wheel control. This patented technology is based on a part called an inertia valve. The purpose of the valve is to open and close bypass ports in the piston depending on the demands of the shock. According to Vic Edelbrock, "We do not pull from a 'pool' of valve codes and use a best-fit approach to shock tuning."
Here's an example: You're driving down a rough piece of asphalt with a few sharp dips. The valve opens ports to reduce rebound damping. This aids the wheels in following the road surface and reduces the input to the driver. When the road is smooth and you're running hard, the inertia valve stays closed, blocking the bypass ports, which keep the rebound-damping rate high to help control chassis motions. In short, if you're running your Corvette hard on a smooth, winding piece of highway, the shock works like a performance shock and handling is firm. If the road gets rough, the shock controls the unsprung mass of the chassis. The shock works wonders on the early model Corvettes, especially over rough road conditions. Although the new-generation Corvette suspension systems are extremely well done, the IAS shock from Edelbrock can be an asset.
Dick Guldstrand, legendary Corvette racer who has driven the Grand Sport and created a business of building and testing high-performance Corvettes, conducted some of the early tests of the IAS shocks. Says Dick, "The [Edelbrock] shocks are excellent and work very good on both early and late models. The early model Corvettes were engineered to run on bias-ply tires, and now we all run radial tires. The Edelbrock shocks work super in handling the change. Also, the Corvettes that are restored and rebuilt are being run faster than they were when they were new because of modern parts and pieces, the shocks handle the speeds by providing a firm feel and flat footprint."
Other features of the Edelbrock shock include: a unique piston-rod material that's extremely corrosion resistant, polyurethane bushings, powdercoated finish, and a high-pressure system prevents the oil from foaming. The shocks are available for most Corvette models and every application (year and model) has been tuned and tested on that particular vehicle with its own unique valve code.