203 To tame the Corvette’s tendency to wander when driven at speed on long stretches of highway, Arkus-Duntov altered the 1956 front suspension to deliver 2 degrees of positive caster. At the time, General Motors designed its passenger cars with neutral caster (zero kingpin angle inclination) to make low-speed steering easier in those days before the mass availability of power assist. Oddly, even though the totally redesigned full-sized Chevy passenger cars switched to modern Glide Ride ball-joint front suspensions in 1955, the crude kingpin front suspension remained under the nose of every Corvette built until 1963.
204 Around back, Arkus-Duntov tailored the rate of the rear leaf springs and shock absorbers to reduce roll understeer from 1956-on. Maurice Olley’s original layout (used on 1953–1955 models) positioned the rear-leaf-spring mounting points so that the leading ends were considerably lower than the trailing ends (as viewed from the side and compared to the horizontal plane). This was done so that with every degree of body roll during cornering the rear axle yawed .15 degrees, effectively counter-steering against the front tires and reducing the tendency of the tail to swing out. Arkus-Duntov changed the spring-hanger locations and reduced Olley’s 15-percent roll-understeer setting to better match the neutral roll steer of the front suspension. The relationship between the roll-steer behavior of the front suspension and that of the rear suspension is referred to as the roll couple. For proper handling, it must be well matched.
205 Despite the significant gain in power in 1956, the 11-inch four-wheel drum brakes of 1955 remained unchanged. However, thanks to GM-sanctioned race efforts in 1956 at Daytona, SCCA road races, the Pikes Peak hill climb, and other venues, a variety of severe-use brake and suspension options arrived in 1957. Every year since, Corvette engineers have included severe-use options to suit virtually every performance need.
206 To announce to the motorsports world that Corvette had arrived and was looking for action, Chevrolet entered the most visible sports-car event held in the United States, the Sebring 12-Hour Endurance Race held in Florida on March 24, 1956. Unlike Daytona, where most of the competitors were amateur hot rodders, Sebring was an SCCA event that brought factory-backed entries from Ferrari, Jaguar, Aston Martin, Porsche, and others. It was the Big League. Four new Vettes were entered, each carrying prototype examples of heavy-duty components that later joined the option sheet.
207 Chevrolet retained racing legend Smokey Yunick and his Daytona, Florida–based Best Damned Garage in Town to help with the early race programs. Despite finishing 15th overall (the top five finishers were Ferrari, Ferrari, Jaguar, Aston Martin, and Maserati), the fact that Corvette even finished the grueling 12-hour event was impressive. Chevrolet’s ad agency, Campbell Ewald, made the most of things, delivering the classic “Real McCoy” magazine ad that appeared in the July 1956 issues of Hot Rod and Road & Track. It was Corvette’s first of many magazine ads touting race success.
208 Supporting the adage that racing improves the breed, the finned brake drums and metallic brake linings used on the 1956 Sebring race cars became part of 1957’s RPO 684 heavy-duty racing suspension option. In addition, RPO 684 also included turbine-like air deflectors placed inside the drums to circulate cooling air, open-faced front backing plates with flexible “elephant-ear” air scoops to force air into the drums, rear-brake cooling ducts, high-rate springs, shocks, and 15 × 5.5-inch steel wheels. Priced at $780.10 (1/4 of the cost of the car), only 51 of the 6,399 Corvettes built in 1957 were so equipped.
209 The RPO 684 big-brake option returned for 1958 with a cool twist. The restyled fascia for 1958 models included a pair of large fighter-jet-inspired air intakes below the quad headlamps, obviously the work of Bill Mitchell’s aircraft-fixated mind. Purely ornamental, they were blanked off for practical reasons, with flat-black paint applied to hide the flat dead ends a few inches inboard. However, with the RPO 684 option, the intakes were trimmed open to feed air to the rear brakes. Huh? Remember, the front brakes used flexible elephant-ear air scoops to direct passing air into the vented backing plates. To get airflow to the rear drum brakes, the grille-mounted intakes fed air into fiberglass conduits mounted to the underside of the front fender and leading down into the hollow rocker panels beneath the doors. From there, the moving airstream was released from the ends of the rocker boxes into square outlets that shot the air into smaller air scoops affixed to the rear-brake backing plates.
210 The 1958 RPO 684 big-brake package required extensive specialized work. Not only did assembly workers have to carefully trim out the fake air intakes under the headlamps, but they had to mount the ductwork to the undersides of the fenders, cut access holes in each end of the rocker boxes, and glass in the square outlets feeding the rear drums. Still priced the same $780.10 as the simpler 1957 setup, 144 were built.
211 If the 1958 Corvette nose’s decorative twin air intakes were perfectly suited for transformation into the RPO 684’s functional brake air-feed ducts, then what about the 1957 big-brake package, where did its rear-brake cooling system ingest air from? Lacking the 1958’s ersatz nostrils, engineers mounted two conical inlet scoops behind the teeth of the simpler 1957 grille. These fed air into 4-inch-diameter flexible hoses that ran along the inner fenders then down to each rocker panel. Once delivered to the rocker panel, the rest of the system rearward to the drums shared the 1958 layout.
212 For 1959, Chevrolet again offered the RPO 684 Heavy-Duty Racing Suspension option, but (except for a handful of early cars) it eliminated the troublesome brake-cooling ductwork and lowered the price from $780.10 to $425.05. Surprisingly, despite the more affordable price, demand remained flat, with 142 takers, two less than 1958 (when 144 were sold). In all instances (the big-brake equipment was offered from 1957 through 1962), the “elephant-ear” air scoops were shipped loose in the trunk for dealer or customer installation.
213 In 1959, all Corvettes were equipped with tubular steel traction bars. Mounted to the top of each end of the rear axle housing and running forward to the articulated frame mounts, they reinforced the front halves of the leaf springs to combat spring wrap-up and axle tramp on hard acceleration and braking. Before Chevrolet added them to all 1959s (regardless of power rating or transmission), companies such as Traction Master made small fortunes selling similar devices to owners of older Corvettes.
214 Proving that bigger isn’t necessarily better, the Cerametallic brake linings used in Corvette’s optional brake packages had less contact area with the drums than the standard organic brake linings. The drop from 158 to 112.5 square inches was due to 1-inch gaps between the friction blocks. Intentionally added by Bendix engineers, they improved heat dissipation and reduced glazing and were also seen on the brake shoes used in NASCAR superspeedway race cars until the advent of disc brakes.
215 Although real knock-off wheels didn’t arrive until 1963, for 1956, the vague suggestion of two-bar knock-off spinners evolved into very realistic-looking copies. These hefty items were affixed to Corvette’s various stamped stainless-steel (snap-on) wheel-cover designs through 1962. Interestingly, Chevrolet adapted the cast-metal spinners for use on passenger-car wheel covers and even for those used on the Corvair Monza. The key difference was that only Corvette-sourced spinners were marked “Chevrolet Corvette.” Others repeated the “Chevrolet” nameplate twice.
216 Arkus-Duntov undoubtedly flinched at Corvette’s simulated knock-off wheel covers. It is ironic that 1957–1962 Corvettes equipped with the optional big-brake packages or the RPO 276 15 × 5.5-inch steel wheels (15 × 5-inch wheels were standard) were stuck with the same austere hubcaps fitted to 6-cylinder 150s and Biscaynes!
217 When the RPO 276 15 × 5.5-inch rims were specified, Chevrolet ensured that the spare tire was mounted to a matching rim, as well. This eased tire rotation. RPO 276 order rates were never high and amounted to 51 in 1957, 404 in 1958, 214 in 1959, 246 in 1960, 337 in 1961, and 561 in 1962.
218 Whitewall tires are commonly installed on restored Corvettes today, but how common were they originally? They were a mandatory option from 1953 to 1956; in 1957 the customer finally had a say in the matter. The 6.70-15 whitewalls added $31 to the total price and were taken by 5,019 out of 6,339 buyers in 1957, 7,428 out of 9,168 buyers in 1958, 8,173 out of 9,670 buyers in 1959, 9,104 out of 10,261 buyers in 1960, and 9,780 out of 10,939 buyers in 1961. In 1962, fashion changed; a thinner, 1-inch-wide band replaced the wide white stripe. Take