The transverse leaf spring...
The transverse leaf spring in early Corvettes keeps them from having truly independent rear suspension. This month we'll address that handicap by installing Speed Direct's Shark Bite rear coilover kit.
During an era when most manufacturers were still building vehicles with straight front axles, GM realized that true automotive enthusiasts sought to corner and brake-as well as accelerate-and engineered the underpinnings of the C2 Corvette (which later carried over into the C3) to facilitate this. This suspension-which combined independent coil springs and control arms up front, and a fixed center section with independent trailing arms in the rear-was unheard of in a domestic vehicle for the time. The technology worked very well, providing arguably the best-handling mass-produced domestic cars of the mid-'60s and well into the '70s. But as technology advanced, the C2 and C3 suspension started to show its age, as well as its drawbacks.
In what was almost certainly a compromise between physical space, economics, and the manufacturing technology of the period, GM chose to use a single multi-leaf spring to support the rear of these Corvettes. Mounted laterally, or transversely, the spring is bolted firmly to the center section of the rear differential in the middle, with each side of the spring supporting the weight of one half of the rear of the car. While this configuration does allow each side of the suspension to travel independently up to a point, one of the drawbacks of the transverse spring is that suspension movement on one side is invariably transferred through the spring, which has an effect on the opposite side. As an example, if, while cornering, the inside rear tire drops due to a low spot or pothole, the outside tire can unload briefly, negatively affecting the car's adhesion. While there are modern composite mono-leaf springs available that help with this problem, we sought to eliminate the transverse spring from our car completely and convert it to a truly independent rear coilover suspension.
There's no doubt that the...
There's no doubt that the midyear-through-C3 independent rear suspension was ahead of its time. One drawback, however, is the transverse leaf spring connecting each trailing arm to the center section of the differential. This month we'll install Shark Bite rear coilovers and eliminate the leaf spring completely.
Since the natural arc of the...
Since the natural arc of the leaf spring can cause a jack to slip, we installed a C-clamp on the spring before using a transmission jack underneath it to relieve tension.
With the spring compressed...
With the spring compressed slightly, the endlink can be removed and the spring dropped. The trailing arm will keep the suspension from dropping excessively. Repeat this procedure for the opposite side.
Having been impressed with the front suspension components from Speed Direct that we installed on Project C3 Triple-Ex last month, we began researching our options on by visiting www.speeddirect.com. The company's Shark Bite rear coilover kit is advertised as being all inclusive, offering either single- or double-adjustable shocks and a multitude of spring rates to accommodate the driving habits and ride-quality preferences of any Corvette owner. Even better, thanks to Speed Direct's proprietary rocker assembly, everything bolts in place of the factory components with no welding or grinding required.
Since our car will see a combination of street, track, and likely autocross duty, we liked the idea of adjustable shock absorbers and a stiffer spring rate for our suspension. If this were a dedicated track car, the double-adjustable shocks would exponentially expand our tuning options, but for this car's purposes, single-adjustable units will keep suspension tuning simpler while still offering far better adjustability than the factory setup.
The other decision we had to make was which spring rate would be appropriate for our car. In general, springs with softer rates offer a smoother ride but sacrifice handling by not keeping the tire firmly planted at all times. As a rule, we're prone to sacrificing the ride quality of our Corvette if it means improved handling, so we opted for the 400-in/lb-rate coil springs. Let's face it: If we cared that much about ride quality, we'd be in a Cadillac, not a Corvette. Even so, springs with a lower spring rate are appropriate for cars that see mostly street duty, and the Speed Direct rear kit offers the best of both.
By simply jacking the car and supporting it, the rear coilovers can easily be removed for spring changes, offering the advantage of running a soft spring in normal driving and swapping in a stiffer one if you plan some autocross or track time on the weekends. We'll likely try different spring rates on our car later on, but for now we'll be using the stiffest springs offered, for maximum cornering capability and traction. (Frankly, we own performance cars because we enjoy driving aggressively, ride quality be damned.)
The leaf spring is held to...
The leaf spring is held to the differential with four, half-inch bolts. Have a friend help you here, as the spring is heavy (around 45 pounds).
You might have to drop your...
You might have to drop your exhaust to remove the rear spring; we were lucky, and snaked ours out one side.
The factory shocks can also...
The factory shocks can also be removed permanently, as they'll be replaced by the adjustable shock absorbers in the Shark Bite coilover system.
With our factory components...
With our factory components out of the way, we removed our new parts from their packaging and took inventory. Our kit was complete and well thought out, including everything needed for the installation.
The first step is installing...
The first step is installing the center bracket on the rearend. This piece bolts right where the leaf spring was attached, using hardware provided with the kit. These, and most fasteners in this kit, need a bit of threadlocker prior to being assembled. The instructions are very clear as to where to use threadlocker, and also give specific torque specs.
Moving outward, the rocker...
Moving outward, the rocker and bracket can be pre-assembled, then installed using the factory provision for the crossmember and supported by a bracket to the differential cover. Only do one side at a time here: if you remove both crossmember bolts, there is very little supporting the center section, and it may drop.