How the Corvette's chassis evolved over more than 60 years

By Mike McNessor - Aug 24, 2020

 

All the right moves

 

Yes, the Corvette is about style and horsepower. But the car's handling is what set the stage for all of those 'Vette versus Porsche 911 magazine covers over the years. No matter what vintage, the Corvette was built with an eye toward being the best-driving sports car for the buck that it could possibly be. So, let's put aside the fiberglass, the engines, and everything else for just a moment and look at how the Corvette's underpinnings have evolved over the years.

 

C1 Chassis

C1 Chassis

 

Generation 1: 1953-'62 If you're a traditionalist, you'll find plenty to like under the first-generation Corvette. The chassis is an adaptation of Chevrolet's 1949-'54 cars, but it soldiered on until the '63 redesign—even after all other Chevrolet automobile front ends were updated in '55. The earliest Corvettes bounced on front coil springs with upper and lower control arms bolstered by a stabilizer bar. While that was fairly cutting edge by prewar or immediate-postwar standards, it still used kingpins to mount the spindles, limiting the range of motion and also making accurate front end alignment tricky. Steering was accomplished by a worm-and-sector style box with a pitman arm attached to a drag link that connected to a third arm. The third arm then, in turn, moved the tie rods that turned the spindles. While the setup wasn't complicated, it wasn't as precise or smooth as you might expect from a sports car, even by 1950s standards. The first Corvettes also had the distinction of being the only ones equipped with a solid rear axle. The Corvette rear used a removable third member like Chevrolet passenger cars through 1964, and the housing was hung from longitudinal leaf springs with direct double-acting hydraulic shock absorbers. While not as exotic as an independent axle, it was a simple, durable, and infinitely rebuildable setup. The foundation for the original Corvette chassis was a sturdy perimeter frame with boxed rails and a massive X-member tying the two sides together. This was a common approach to eliminating chassis flex in an open-top car, but it added weight.

 

C3 Chassis

C3 Chassis

 

Generation 2/3: 1963-'82 The Corvette chassis took a technological leap forward for 1963, and the design would endure until all-new underpinnings arrived two decades later. It wasn't mid-engine, as Zora Arkus Duntov would've liked, but it incorporated a lot of what he'd learned in racing. The C2/C3 Corvette still used a boxed full frame, but that's where the similarity with the previous car ended. The big X-member was eliminated in favor of welded steel rails connected by five ladder-type crossmembers that helped make the chassis 90 percent stiffer. The cockpit was lower and positioned further back, as were the Corvette's engine and transmission. This helped bring the car closer to a 50/50 front-to- rear weight balance and lower the center of gravity. With equal spring rates, the '63 chassis had a more balanced feel and would roll 18 percent less in a turn than the '62. The front end was modernized with spherical ball joints and shared some parts with the production passenger line. A recirculating-ball steering box turned the front wheels via relay-type linkage (mounted behind the front wheel center lines) and a steering damper was incorporated on cars with manual steering. Power assist was also available for the first time. The big news was the Corvette's independent rear suspension that was innovative and elegantly simple. The differential carrier was mounted to the frame, helping keep the car lower, reducing rear unsprung weight, and keeping the driveshaft angle constant. It was a three-link design where the half shafts doubled as the upper links, simple strut rods bolted below the differential housing extending to each wheel were the lower links while control arms on each side served as longitudinal links. A leaf spring mounted parallel to the rear axle and bolted below the differential housing served as a no-fuss stand-in for more elaborate and expensive coilover units. The 1963-'82 Corvette chassis isn't perfect, but it was ingenious in its use of conventional parts to achieve an exotic result and it put far more expensive sports cars from Europe on notice.

 

C4 Chassis

C4 Chassis

C4 Chassis

C4 Chassis

 

Generation 4: 1984-'96 The newest Corvette in over a decade used fiberglass for more than just the body. At the heart of the C4 chassis were reinforced- fiberglass or "filament wound glass epoxy composite" monoleaf springs—front and rear. (The rear monoleaf made its debut under Corvettes for 1981.) The new springs were not only simple, but very lightweight: the front monoleaf weighed one-third what coils weighed while the rear was 33 pounds lighter than the multileaf steel spring it replaced. The reinforced fiberglass springs were also exceptionally strong, and performed in two ways: When the car bounced, the springs flexed and flattened out; when the vehicle rolled in a turn, the springs bent into an S shape, which added roll stiffness, allowing designers to minimize the size, and weight, of the stabilizer bars. The weight savings continued with the liberal use of aluminum throughout the chassis: The steering knuckles and A-arms up front, the torque arm, the driveshaft, the halfshafts, the differential housing, the rear crossmember, and the brake calipers all were aluminum. The C4's independent rear axle used a five-link design—replacing the old three-link setup—with aluminum trailing arms, as well as adjustable rods for toe and camber. The new Corvette also did away with the ladder frame in lieu of a "uniframe," or backbone chassis, made of galvanized steel sections welded together. A cage was incorporated into the chassis that included the windshield frame, door jambs, rockers, and a targa bar on coupes. The final improvement over the C3 was the substitution of the conventional steering box with a rack-and-pinion unit that offered a 15.5:1 ratio and could go lock to lock in 23/4 turns (13:1 and 21/4 turns with Z51). The C4 set the stage for Corvette chassis design to come, but it had some drawbacks. The open roof (without T-wtops) necessitated high sills, which made ingress and egress difficult. The suspension was bone-jarring stiff, particularly in the earliest C4s, and led to a lot of squeaks and rattles.

 

C6 Z06 Chassis

C6 Z06 Chassis

 

C6 Chassis

C6 Chassis

 

Generation 5 and 6: 2005-'13 The C5 chassis was based around the design of the C4, but vastly improved in ways that translated into a more refined driving experience. The C5's uniframe was lighter and more than four times stiffer than the C4's, largely due to its hydroformed rails. The C4's frame rails were each made of more than a dozen separate components welded together, whereas the C5 used a pair of 13-foot-long continuous rails hydroformed in a die using fluid pressure. Another big change was the use of a rear transaxle in the C5. By moving the gearbox to the rear, the weight distribution nearly hit the 50/50 sweet spot at 51 front/ 49 rear, and freed up space in the cabin. An enclosed stamped-steel driveshaft tunnel (a torque tube) between the engine and the transaxle made the chassis even stiffer. The suspension hard parts were made out of aluminum, as in the C4, and transverse mounted leafs handled the bumps. The front suspension used revised components, while the rear was an entirely new design with upper and lower A-arms and constant-velocity joints replacing the old five-link setup with universal joints. Also introduced on the C5 (in 2003) was Magnetic Selective Ride Control. The system used shock absorbers filled with magnetorheological fluid (i.e., the fluid is magnetic because it's filled with iron particles) and pistons that incorporated electromagnets. When the electromagnets were activated, the magnetic force acting on the iron particles in the fluid stiffened the shocks. Without a doubt, the C5 chassis transformed the Corvette. The car was easier to enter and exit, and more comfortable to drive, plus the ride was less punishing—even the track-ready Z06. For the 2005 redesign, the Corvette chassis was shortened by about 5 inches and strengthened, while its wheelbase was lengthened by about 1 inch. The C6's suspension design echoes the C5's, though the components were redesigned and no parts carried over. The biggest news was in the arrival of the Z06 and ZR1 C6s, which utilized aluminum chassis with a magnesium roof structure and engine cradle. The alloy chassis weighed a feathery 278 pounds compared to 414 pounds for the steel C6 structure.

 

C7 Chassis

C7 Chassis

 

Generation 7: 2014-'19 Since its inception, the Corvette's engine had been in the front and it rode either partially or totally on leaf springs. The C7 would be the last of that breed and, in terms of chassis design, the most sophisticated. All C7 Corvettes were based on an aluminum uniframe, though it was markedly different than the foundation of the used hydroformed rails with a uniform wall thickness. The new uniframe was more customized as each main rail was made from five aluminum segments. The gauge of the material varied from 2 mm to 11 mm, putting strength in places needed most and making other areas lighter. The segments were then joined together using a mix of spot welds, fasteners, adhesive, and laser welds. At the front and rear, hollow cast aluminum cradles for the chassis components were used for additional weight savings and rigidity. The result was a nearly perfect 50/50 weight distribution, a lighter, stiffer chassis than the previous generation, and a structure so solid that no additional bracing was needed for the convertible. Also new was an electronic power steering system with variable ratios and effort to suit the driver, while an electronic limited-slip differential was also part of the Z51 package. The computer controlled diff could instantly vary the amount of lock needed, depending on the conditions. The suspension front and rear mirrored the design of the previous series, with cast aluminum upper and lower control arms and traverse-mounted leafs fore and aft. If the traditional Corvette front-engine layout had to end, at least it did so on a high note.

 

C8 Chassis

C8 Chassis

 

Generation 8: C8 2020- Duntov's vision of a mid-engine Corvette finally materialized with the arrival of the C8 for 2020. There's no room for debate here: Placing the engine nearer to the center of the chassis in a rear-wheel-drive car makes for a more balanced package and improves traction for acceleration and braking. To make the C8's chassis both lightweight and strong, designers turned again to extensive use of aluminum for its construction. In order to keep the side sills low for easier access to the cockpit, the center tunnel was made the backbone of the chassis and was constructed out of extruded aluminum, as were the rocker supports, windshield posts, and more. Die-cast aluminum was used for the rear engine cradle and rear suspension mounts, as well as the front suspension supports— in fact, there were 20 cast aluminum components used throughout the chassis. Aluminum stampings were used for brackets, floor supports, the windshield header, and more. To join all of these alloy chassis parts, GM made extensive use of adhesive and fasteners, as well as rivets, with less reliance on welding than in previous aluminum chassis. The suspension, front and rear, was designed with forged upper and cast lower control arms with coilovers providing the bounce, thus relegating the Corvette's signature leaf springs to history. A stabilizer bar was made standard issue in the rear while the front could be equipped with a power lift to give the nose more clearance over speed bumps or when negotiating low driveway entrances. There's no question that the C8 represents the pinnacle of Corvette development and technology. Can it live up to the legend created by its predecessors? Only time will tell.


 
PHOTOGRAPHY PROVIDED BY GENERAL MOTORS
 
 
SOURCE: HEMMINGS