The assembly-plant changeover from St. Louis to Bowling Green in 1981 brought a switch to a more plastic-infused formula for the SMC body panels. Published figures vary, so without the capability to weigh both factory-stock '80 and '81 models, it's difficult to provide an accurate comparison of the weight differences between traditional fiberglass and SMC-bodied cars. From the numbers we researched, it appears the '81s were about 100 pounds lighter than their '80 counterparts. That's not all attributable to the SMC bodywork, however, since the change to a fiberglass mono-leaf rear spring for '81 accounted for about a 35-pound reduction. Nevertheless, newly formulated body panels helped lighten the Corvette--and it was the same basic formula used throughout the C4 generation.
C5: Getting Serious About Weight Savings
The introduction of the C5 in 1997 represented one of the rare instances in the automotive world where the next-generation model weighed less than its predecessor. Even more impressive, the '97 Corvette was larger overall--longer and wider--than the '96 model, yet it tipped the scale at about 3,220 pounds with a manual transmission, compared with the '96's 3,300-pound curb weight.
A number of contributors helped drive down the C5's weight, including the use of SMC body panels that had a higher content of plastic than ever before. The material, which is basically the same as used in the C6, was composed of about 40 percent resin--polyester, vinyl ester, styrene, or a blend of all three--33 percent calcium-carbonate filler, 20 percent chopped fiberglass, and the remaining 7 percent resins and hardeners that improve the out-of-mold surface finish.
The C5's panels were exceptionally light, but so was the Corvette's all-new chassis, which used beefy rails and hydroformed sections to provide strength with less complexity and weight. In fact, the floor sections used a sandwich of materials including featherweight balsawood to minimize mass, a feature that continues with the C6.
The Gen III small-block can't be discounted in the weight savings and overall greater balance of the C5. Compared with the old-school small-block it replaced, it delivered a lightweight aluminum cylinder block and a composite intake manifold that weighed less than 10 pounds.
In 1999, the Corvette "hardtop" model took weight savings and performance to a new level. By replacing the signature--and heavy--hatchback glass with a more formal-looking roof section made of an even lighter-weight SMC material, curb weight dropped to about 3,155 pounds. There hadn't been such a lightweight Corvette since the early C2 days, when comparatively heavy airbag modules, electronic chassis-control systems, and structural crash-safety features weren't even sparkles in the eyes of engineers.
The hardtop model, of course, was the foundation for the C5 Z06, whose weight was further pared to 3,120 pounds by shedding some of the base models' luxury features for a more purposeful driving experience. The '04 Z06 Commemorative Edition was lighter still, with a carbon-fiber hood that was 10.6 pounds lighter than the standard SMC piece. Taking that weight off the nose of the car improved its overall balance as well. It was the perfect send-off for the influential and technologically advanced C5 generation.
C6: Aluminum Chassis, Carbon Fiber, and More
Although the C5 and C6 generations share basic chassis layouts, the C6 brought additional changes in the quest for reduced weight, not the least of which was the elimination of the Corvette's trademark retractable headlamps in favor of simpler, lighter-weight fixed units. The plastic-intensive SMC body panels remained, although surprisingly, the rear fenders were made of conventional steel. That's right--steel fenders on a Corvette. It was a first.
The base '05 Vette weighed in at 3,240 pounds--only about 20 pounds more than the first C5 models of 1997, despite more safety-enhancing structure under the skin and generally more standard content. A year later, the C6 Z06 brought with it an aluminum-based chassis structure and carbon-fiber body panels that represented the most significant targeted weight-reduction initiative in the Corvette's history. With its 505-horsepower engine and a curb weight of less than 3,200 pounds, the Z06 had an enviable power-to-weight ratio that most higher-priced European exotics couldn't match.