Updating Your C2-C3 Corvette’s Handling With Detroit Speed (Part II)

There are so many options available to upgrade a ’63-‘82 Corvette chassis. This gives the owner different choices, depending on their expectations and whether they intend to remove the body from the frame. It used to be, if you wanted to base your midyear or shark’s chassis on an entirely new, better-handling foundation, you needed to remove the original frame and all its dated suspension technology. Detroit Speed has changed all that, and has recently updated its DECAlink IRS chassis, allowing it to be installed without the need to remove the body from the frame.

The DECAlink chassis updates the entire geometry of the Corvette’s rear suspension. It utilizes much newer technology, which improves handling, durability, and greatly eases maintenance.

Installing the DECAlink system affords the end-user all the benefits that a fully-adjustable, 10-link chassis can bring to a car’s handling. The cross-axis pivot bushings are installed at all pivot points, which allow the IRS to fully articulate without binding, giving your Corvette a new level of performance and accurate handling. Alignment, ride height, and handling characteristics can be easily adjusted throughout the system, and the beefy components come together to build a solid foundation to make your vintage Corvette perform like a modern sports car.

The rear differential is now held in place within the upper and lower cradle assemblies. Coupled with the urethane bushings, this greatly strengthens the stability of the unit under heavy acceleration.

We brought you Part One, which showed the various mounting-modifications necessary to install the system. With everything in place, it was now time to put things together and fit them to the underside of our C3 Corvette. While the install can be done with the body on, it is obviously much easier to have the car on a lift and have a transmission jack handy for the heavy lifting.

Starting At The Rear

The first thing is to upgrade the output shafts on the OEM differential. DECAlink allows Corvette owners to use the factory 17-spline differential assembly, but the DECAlink system is designed to use bolt-on, CV-joint-style shafts. That means we needed to change out the rear differential’s U-joint-based output shafts for flanged units. Now would be a great time to check the condition of all the components within the diff, and also make any upgrades to the gearing or differential unit, if you so desire.

DECAlink will work with the factory 17-spline differential, but the output shafts will need swapped out for flanged units.

Once you get the differential sorted, it bolts into the lower-cradle assembly using the factory bolt locations. The housing sits into the lower cradle assembly, which helps keep it planted; and removes any suspension loads other than the differential’s task at hand, getting power to the wheels. The suspension components now bolt to the upper and lower cradle assemblies to ensure proper operating geometry and keep the ever-changing forces of operation in check as the suspension moves throughout its travel. To further help with stability, everything is now urethane-bushed to prevent movement under heavy load, a trait the original differential exhibited from the factory.

Adding Adjustability

While having a solid foundation is key to optimum handling, a suspension also needs the ability to move freely throughout its entire range of travel. The 10-link system gives the chassis the ability to move without binding. It also allows for adjusting rear anti-squat geometry and roll-center height engineered into DECAlink. Choosing between the set rate, DSE/JRi “Detroit Tuned” coilover shocks — which allow for spring rate tuning and ride height adjustments — or upgrading to Detroit Speed’s single, or double-adjustable shocks, gives options to suit the end-user’s preferences and driving style.

The various control arms are assembled to a base length and use OEM cross-axis pivot bushings at all pivot points. All suspension-link lengths are adjustable by threading the end-links in or out. Once you’ve assembled the control arms used to keep the hubs aligned, systematically installing them onto the upper and lower cradle assembly will provide a connection point for the free-floating hubs on each end of the driveshafts.

The differential and lower-cradle assembly are joined with the upper assembly, already attached to the underside of the vehicle. This boxes-in the differential and triangulates the connection between the front mount of the diff and the various mounting locations for the upper-cradle assembly.

The driveshafts on the DECAlink system are heavy-duty CV-joint-style shafts. The fact that the hub is now controlled by the various control arms means the driveshaft is no longer subjected to the weight of the vehicle as it was in the original design. Also, the mounting geometry of the 10-link system keeps the tire’s alignment specs much more closely within spec throughout the suspension’s travel.

The mounting position for the trailing arms is modified from the original points to remove the axial rotation of the hub as the suspension moved up and down. The addition of bars to adjust toe and camber give better stability throughout the suspension's range of movement, and increased adjustment setting capability.

The sealed outer bearings in the forged uprights have proven themselves very reliable for several generations of Corvettes, and ease maintenance over the C2-C3 units. This is because they no longer need any setup or shimming, should they ever need replaced. The new driveshaft and hub assemblies mate together much like a modern auto of today, where U-joint clamps have given way to splined shafts and a single external nut.

The shocks can be tailored to your liking via different spring rates, simply contact a Detroit Speed customer service associate when ordering. The shocks feature an additional fluid canister and come with a Torrington bearing and a spanner wrench to simplify ride height adjustment later. Detroit Speed also offers optional billet mounts to attach the canisters to the car's chassis.

The coilover shocks are assembled and then installed onto the chassis. The DECAlink system comes with 8-inch tall coilover springs with a rate of 550 lbs./in. While final tweaking of ride height and shock responsiveness (single and double-adjustable shocks only) will have to wait until the car is sitting on its wheels, the end user can choose to go with softer or firmer springs, depending on their preferences. The Detroit Speed Corvette is mostly used for competition and they have experimented with many different spring rates over the years. Our contact at Detroit Speed reports they have found it best to use a heavier spring rate in the front with a lighter spring rate in the rear for autocross.

The way the DECAlink was designed, we really haven’t changed from our initial alignment specs between street driving and autocross events. - Dan Oddy, Detroit Speed

Detroit Speed’s Dan Oddy suggests, “This is a typical spring rate setup when your vehicle is used for competitive driving. However, it does depend on the driver to decide what spring rate they feel the most comfortable with if competing with their Corvette. Detroit Speed would be happy to help the customer select a different rate depending on how they plan on using their Corvette.”

The kit also includes Torrington bearings and a spanner tool for easy ride height adjustments. The DECAlink system is also designed to use either Wilwood or BAER brakes originally designed for the C6 Corvette, so enthusiasts have options to match their car’s stopping, as well as its turning.

Final Fit & Finish

With all of the components installed, it’s almost time to hit the open road. There are alignment specs in the instructions, giving you a recommended ride-height, static camber, and toe setting to maximize the performance of your DECAlink IRS system. We asked Dan about how the settings might vary between street and competitive driving. “The way the DECAlink was designed, we really haven’t changed from our initial alignment specs between street driving and autocross events,” he said. “However, it comes down to preference. We don’t typically run too much static negative camber in the rear suspension, in order to allow as much of the tire width to stay in contact with the pavement.”

The splined haflshafts mount to the new hubs with a central nut. Once everything has been installed, you can see how everything works to ensure the hub stays level and square throughout the entire range of motion. Additionally, since the hub is supported by the numerous link rods, the weight of the vehicle is no longer transferred through the halfshaft to the differential.

As an added bonus, the DECAlink system mounts all chassis components inboard, to allow for wider tires and wheels without having to add fender flares. Detroit Speed reports that up to a 275-width tire on an 18-inch wheel can still be stuffed under the factory rear quarter-panel, using its DECAlink suspension on a C3 Corvette.

The DECAlink IRS replaces the entire rear suspension of your C2-C3 Corvette with a modern, race-proven alternative, which is just as beneficial on the street as it is on the track. All of today’s OEMs know the benefits of a stable suspension, and go to great lengths to put one under each car they sell. Now, your vintage Corvette can have one too!

When all is said and done, you are basically replacing a rear suspension that was designed over 50 years ago with a totally re-engineered version, designed to handle and perform like a modern C6/C7 Corvette. Your ’63-’82 Corvette’s handling will have a modern, high-performance feel as it hugs the road in straight-line acceleration and high-speed cornering. Now, you can have all the benefits of a newly-designed suspension under your vintage Corvette, and thanks to Detroit Speed, you no longer have to remove the body from the frame to get it.

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About the author

Andy Bolig

Andy has been intrigued by mechanical things all of his life and enjoys tinkering with cars of all makes and ages. Finding value in style points, he can appreciate cars of all power and performance levels. Andy is an avid railfan and gets his “high” by flying radio-controlled model airplanes when time permits. He keeps his feet firmly grounded by working on his two street rods and his supercharged C4 Corvette. Whether planes, trains, motorcycles, or automobiles, Andy has immersed himself in a world driven by internal combustion.
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