Photography by Huw Evans and courtesy of Zip Corvette.
Sports cars are often purchased for a number of reasons, but one of the primary ones is handling. Feeling the vehicle hug the road through the corners at decent speeds is enough to tingle anybody’s spine. In Corvette circles, the situation is no different. As a result, suspension servicing and upgrades are often a high priority amongst many owners and enthusiasts. Having said that, like anything else, maintaining or upgrading components isn’t always an easy decision. In this article we take a look at the basic suspension system as found on C2 and C3 Corvettes, analyze both its strengths and weaknesses, and discover who out there offers replacement parts to address these problems.
1963-82 SUSPENSION DESIGN
Upon its introduction, the 1963 Sting Ray broke new ground in terms of chassis and suspension design. Unlike the 1953-62 Corvettes, which used an X-frame, the Sting Ray featured a ladder-type design with five crossmembers. This design was chosen because it was much more rigid, and would help absorb the lateral stresses imposed by the Corvette’s now fully independent suspension.
Speaking of that suspension, at the front the Sting Ray stuck with GM’s proven long/short arm double wishbone suspension with the coil springs wrapped around the tube shock absorbers. A front sway bar was standard fitment. At the back, Zora Arkus-Duntov came up with a brand new setup. Choosing an independent rear suspension enabled the rear tires to remain as perpendicular to the ground as possible at all times, maximizing the contact patch whether in a straight line or under cornering. Considering cost constraints, it’s quite impressive that Duntov managed to push through his IRS design for 1963. At the time it was also a fairly ingenious setup. The differential was attached to the frame via rubber isolators and a center-mounted trailing link, with a pair of radius rods that double as lateral control arms extending out from the back of the differential housing on each side. Above them was a single, transverse, 9-leaf spring, whilst the axle halfshafts doubled as upper lateral arms. In addition there were a pair of lower trailing arms linking the wheel hubs to the frame on each side and a pair of camber rods behind the spring that attached to a bracket at the top and each wheel hub at the bottom. It was a fairly compact design, and despite its greater complexity, actually lighter than the old leaf-sprung solid axle setup on the 1962 Corvette.
Moving the engine further back in the car also resulted in a 49/51 percent front/rear weight distribution, and combined with the suspension, it put the Sting Ray in an entirely different league when it came to handling. Road & Track magazine, which at the time had a penchant for British and European sports cars, noted that “the new Corvette will know few peers on road or track–it ought to be nearly unbeatable.” And indeed, it wasn’t long before the new Corvette was proving a force to be reckoned with in motorsport, in fact on only its very first outing, a Sting Ray coupe took the checkered flag at the Three Hour Invitational road race at Riverside in the fall of 1962!
For the 1965 model year the Corvette received its first big-block engine, which weighed more than 650 pounds. The car’s weight distribution was altered (now 51/49 front/rear), requiring stiffer front springs and bigger front and unique rear sway bars to compensate, though the rest of the suspension was unchanged.
When the C3 Corvette debuted in 1968, despite the “wasp-waisted” styling, there were surprisingly few changes to the chassis and suspension, though spring and damping rates were altered and radial tires became available beginning in 1973. For 1980, in an effort to save weight, the Corvette was offered with a composite leaf spring at the rear, which was stronger and lighter than the previous steel spring. This new unit was also far more durable and not prone to fatigue and sagging, which could happen with the older steel spring over time. In addition, the 1980 Corvette also adopted a lighter, aluminum differential carrier, which also reduced weight on the rear suspension. This, combined with other weight savings and wide tires (P255/70R15), made these cars rather capable handlers, especially considering the basic age of the chassis and suspension design by this time.
For the era, the 1963-68 Corvette suspension system was fairly advanced and capable. However, it was still created under cost considerations and besides its strengths (good handling, compact design, relative simplicity), it also has a few shortcomings, which tend to manifest themselves over time and use.
Starting at the forward end, the lower control arms are one of the biggest problem areas. Because the arms take a pounding at the pivot point where they attach to the K-member, the bolts and bushings tend to wear out. The bushings can collapse and the bolts tend to work their way loose. So if you haven’t taken a look at them, do so at the earliest opportunity. Sometimes the bolts can just be tightened, but if the Corvette is still sporting its original rubber bushings, replace them, or if originality isn’t as much of a concern, use harder polyurethane replacements. Another problem area concerns the front ball joints. They were originally attached to the lower A-arms by rivets and over time tend to loosen, which will cause the front wheels to wander on the road.
One other problem area concerns the upper arms. The rubber cone bushings will deteriorate and eventually split, but are easy to replace. The sway bar links are another common problem. The upper part of the link, where it attaches to the control arm, gets more than its fair share of abuse due to the car’s suspension geometry. Eventually the rubber link bushing at the top will crack and split. You’ll be able to feel this, because the Corvette will tend to roll a bit more through the corners. Be aware that most replacement link kits feature larger bolts, so if originality is important and the factory link bolts are in decent condition, you can clean and re-use them.
Given the added complexity of the rear, there are a few more trouble areas. First up are the lower trailing arms. On big-block cars or Corvettes with high-torque engines, additional stress was placed on the arms during standing-start drag launches. The arms could bend and the arm-to-frame bushings could wear out prematurely, which not only affects straight-line traction but also handling, since it causes excessive play on the joint. Even if the car hasn’t been subjected to such abuse, the bushings tend to become brittle over time, and can eventually collapse. Also, the mounting holes can also rust as well, which can eventually cause them to seize (you’ll know if they’re bad because the car will be squeaking over every bump and imperfection in the road). You can clean and re-drill the holes and install new bushings. Although some recommend using polyurethane, rubber replacements are actually preferred on a stock or mild street Corvette, as they are best able to strike a balance between decent ride quality and optimum handling (urethane bushings can cause the rear end to bounce on rough roads). When fitting new bushings, you need to make sure the ends are flared for a proper installation.
Another problem on 1963-82 Corvettes concerns the upper shock mounts. These attach to a bracket on the bottom of the floor, but the bracket mounts weren’t particularly well located from the factory. This could cause problems with tire wear, either if the car was lowered at the rear, often by shortening the spring, or simply from use. Many owners have found it necessary to check and relocate the bracket-to-shock mounts, to prevent excessive tire wear. Another major problem concerns the halfshafts and radius rods (which perform the upper and lower control arm functions respectively). Given the levels of performance offered (particularly from the mid-1960s through the early 1970s), the stock shafts are not that durable. They were constructed from 2.5 to 3-inch thick steel and although the 1350-type universal joints weren’t bad, the axle-to-joint supports were very weak with only a single U-bolt linking them together. If the car was drag raced frequently, the bolt could start to work its way loose causing the half shaft to disconnect from the joint. Beginning in 1965 with the advent of the Mark IV big-block V-8, a retaining strap and cap screws were used to keep the halfshaft in place, in addition to the U-bolt, but it was only a marginal improvement (and again was only offered on big-block equipped cars).
The camber rods also present a problem, in that to maintain the max tire contact patch, they need to be parallel with the halfshafts and radius rods. However, the stock camber bracket doesn’t allow for a great deal of adjustment. This causes problems as the shocks wear out and the shafts and radius rods are now positioned at different angles to the camber rods. Lowering the car often has the same effect. The result is excessive negative camber, and increased tire wear on the inside edge of each wheel.
Give the popularity of C2 and C3 Corvettes, there are a number of suspension upgrades available to address the shortcomings of the factory suspension.
Zip is one of the most prolific suppliers of replacement parts for these cars. For the front suspension, Zip offers a complete line of parts from rebuild kits, to shocks, bushings, and ball joint replacement parts, including grease fittings, correct reproduction or replacement upper and lower ball joints, as well as the ball joint rivets, nuts, and bushings. One nifty product is the Upper Ball Joint Rivet Fixture. This allows for a quick installation of a replacement ball joint; it looks factory but addresses the sloppiness of the OE riveted setup, helping provide better handling, longer life, and greater piece of mind when driving.
Front coil spring sag is something that happens to any car over time and use, including Corvettes. Give the popularity of correct restorations, replacement coils that mirror the originals are widely popular. Do bear in mind that specific springs were originally used depending on the application. GM identified the different springs via a two-digit code. On 1963-67 cars, springs were labeled ED, those for big-block 396/427 (EB), cars equipped with the F40/F41 and aluminum-head L88 engines (EA) and (EF) for cars equipped with A/C. From 1968 the codes were changed–HS/HT (for 327/350-engined cars) and HU/HV (for 427/454 powered examples). Correct spring labels are also available from sources like Zip Corvette, Mid America Motorworks, and Corvette Mike–and for that true factory look, correct code labels are also offered.
The factory-style Delco front shocks are also available through various aftermarket sources, but if it’s performance you’re after, a modern monotube gas shock can provide precision damping ability the stockers can only dream of. Bilstein offers a line of performance shocks–either separately or as a complete kit–that includes front and rear dampers, plus bushings, retaining washers, and nuts. Other popular shocks for these cars are KYB gas monotube shocks (which have a lifetime warranty) and Sachs gas dampers (Sachs is the OE supplier for shock absorbers on the C6 Corvette).
For those that like to road race their Corvette, coilover suspension packages are offered for these cars. Speed Direct offers its Shark Bite coilover kit for 1963-82 cars, in either single- or double-adjustable configurations. The shocks feature four inches of total ride height adjustment, and are made from aluminum. Combined with the Shark Bite lightweight aluminum control arms, they shave a considerable amount of poundage off the nose.
At the back, one of the biggest improvements you can make is to repair or replace the transverse leaf spring. A worn spring alters the ride height, which adversely affects handling and tire wear. For OE-grade replacements, one of the best sources is Detroit Eaton Spring, which manufactures new leaf springs for just about any car or truck that was originally fitted with them. If saving weight or improving performance is on your list, you can always upgrade to a fiberglass spring. These reduce unsprung weight at the rear and are less prone to fatigue. Zip Corvette stocks them and they come with all the required mounting hardware, plus adjustable outboard spring bolts and a five-year limited warranty.
To further help stability and performance, consider bolting in an aftermarket rear sway bar. Addco provides a replacement rear sway bar kit for 1963-82 Corvettes that features a heavy-duty bar, links, brackets, and polyurethane bushings to reduce body roll.
Like with the front, shocks are widely available for the rear of these cars, but if you really want to take handling to the next level and cost isn’t an issue, you can convert the factory setup to coilover shocks. Speed Direct now offers a Shark Bite adjustable rear coilover kit that is a true bolt-on upgrade. Like the front, single- or double-adjustable shocks are available with specific rate springs depending on the desired level of ride or handling. These kits aren’t cheap but there are few better alternatives when it comes to providing the ultimate street/handling setup.
Although we’ll only touch the surface since the axle shafts are also part of the driveline upgrades, it is worth noting that stronger drive axles are available. Tom’s Differentials, a noted Chevy 12-bolt rearend specialist, sells stronger steel halfshafts designed to mate with strong, truck-type 1480 U-joints and the required flanges, as part of a 12-bolt IRS conversion. These 3.5x0.134 shafts are built to withstand the rigors of repeated drag launches and are certified by the NHRA for cars that run 11.99 or quicker in the quarter-mile. Stronger inner and outer drive, 17-spline axles are also available, and to compensate for camber changes during hard launches, Tom’s also sells thicker camber rods and stronger camber rod brackets.
One final aspect we’ll touch on in this article concerns the rear trailing arms. Hard abuse can cause the stockers to flex, and can damage the pivot points where they attach to the frame at the front. Worn axle bearings can also be a problem because the bearings and wheel hub assemblies slot directly through the arms. Complete new or rebuilt factory lower trailing arms (that include the wheel hubs and bearings) are available from sources like Zip Corvette, or if you’re looking for something stronger, beefy, offset lower arms from companies like Tom’s Differentials and Zip are a good choice, especially if you plan on running wider than stock rear tires, adding more power and torque, or plan on drag racing (those from Tom’s are NHRA certified).
Special thanks to Justin Abbott at Zip Corvette and Legendary Motorcar Company for their assistance with this article.
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