Ultimately, Webb says, the limiting factor on the road that morning wasn’t the car—its 5.9-L twin-turbo V8 was still good for at least another 20 mph, SSC engineers estimate—but the conditions. “We didn’t have six lanes on a test track to play with,” says Webb, who competes in multiple race series, including Le Mans and the World Endurance Championship, in addition to being a test and stunt driver. “This is two lanes, and if you get pushed over one lane you only have 6 inches before it’s game over. So it was me deciding to back out of the run. In ideal conditions, we could have gone faster.”
The effort is the culmination of a 10-year development process for the $1.6 million Tuatara, which succeeds the company’s SSC Ultimate Aero. That car had set the record in 2007 for fastest production car, with a speed of 256.18 mph. SSC approached the design of the new car with the record in mind, Shelby says, and the team paid particular attention to the engine—developed in collaboration with Nelson Racing Engines—and aerodynamics, as you’d expect. They had to be more than just good enough to keep the car on a racetrack: The car needed to be slippery enough for high-speed straight-line driving and able to generate enough downforce to stick to the pavement, yet it still had to look great to collectors and the hypercar-admiring public.
That challenge fell to designer Jason Castriota, whose background includes time at Italian automotive design houses Bertone and Pininfarina, where he contributed multiple Ferrari and Maserati production and concept vehicles. He says his chief challenge with a car engineered to exceed 300 mph included managing the airflow both externally and internally, the latter due to the tremendous heat generated by the engine. Too many radiators and extra cooling fluid would increase weight, so Castriota created a network of channels that funnel air into and out of the car. The team adopted an extended wheelbase, an ultracompact engine configuration, and a passenger compartment that resembles a capsule, all in the service of controlling airflow for cooling the engine and brakes, increasing downforce, and minimizing drag. The car has a coefficient of drag of 0.279, which itself is a record for its class—a Jeep Wrangler scores a chunky 0.454 by comparison.
The total downforce at 312 mph—the maximum they simulated—was 770 pounds. Think of downforce as the aerodynamic opposite of the lift generated by an airplane’s wing, and Shelby estimates it would have been well over 800 pounds at 331 mph, Webb’s top speed.
Aerodynamic balance is also essential, in that it determines the “center of pressure” in the car—where the car is pushing down the most. That should be happening directly behind the driver, but in early iterations of the car, computer simulations indicated that at high speed, over 300 mph, most of the downward aerodynamic force was occuring 10 car lengths ahead of the vehicle, as it pushed air forward while moving through it. “We had to claw back our center of pressure to get it where we needed it to be,” Castriota says. “It was a million little adjustments and reshaping of the car to walk it back.”