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In early November of last year, Koenigsegg factory driver Niklas Lilja spent a day blasting the company’s Agera RS hypercar up and down an arrow-straight stretch of smooth asphalt near Las Vegas. His lead foot got the job done: The car set five separate speed records, including the highest top speed achieved by a production vehicle (a two-way average of 277.87 mph) and the highest speed on a public road—a mind-warping 284.55 mph. (Yes, the Koenigsegg was running on a closed course.)
Everything about the car is customized and tuned for its singular purpose—going fast. Its shape is based on the specs for a Le Mans GT1 racer, and thus optimized for the ridiculously long straight at the series’ titular home track. Its mid-engine placement and air intakes are designed to enhance stability at high speeds, so much so that the faster it goes, the more stable it becomes. Its suspension is engineered to minimize the kinds of destabilizing up-and-down movement experienced at triple-digit speeds that wouldn’t even be noticed at the speed limit. And the aero—oh, the aero. It is, of course, fully active, with opening flaps and a moveable rear wing all engineered to keep this Koenigsegg firmly on the ground.
But while the hardware in the car is pretty thoroughly not off-the-shelf, the software—not the computer programming, but the four rubber bits at each corner—actually is. The Agera RS runs on Michelin Pilot Sport Cup 2 tires. This is the same tire fitted to the Bugatti Chiron, though it’s tweaked specifically for each car. For the speed-record run, though, the team didn’t use a special set or a tire engineered specifically for a high-speed run; noo racing slicks, no funky compounds. It was the same exact tire that comes with the car. This is somewhat surprising, and kind of scary—though in a good way. After all, if a set of “standard” street tires can handle nearly 285 mph, what else can they handle?
During the North American International Auto Show in Detroit this week, Christian von Koenigsegg and Michelin product manager Eric Schmedding took a break to discuss how the tires stood up to the blazing speeds the Agera RS encountered in the desert outside of Vegas, as well as how much farther the rubber can theoretically be pushed. Having been in the performance-car business for a quarter century, von Koenigsegg has learned not to give tires short shrift.
“Our car doesn’t end where the wheel ends,” von Koenigsegg said. “Our car ends at the tarmac, and the tire is an integral part of our engineering.”
His partnership with Michelin has existed nearly as long as the Koenigsegg brand has been alive; for this record attempt, the tire manufacturer worked with the vehicle engineers beforehand to ensure that the tires could withstand the stress.
“We never intended these tires to go 270 mph,” Schmedding said. “But while they’re rated for much lower speeds, we also know their true capabilities are much higher.”
Schmedding and his team first sought out the basic details of the car’s performance at speed—its weight, suspension geometry, aerodynamic load, and other factors. All of this would factor in to their estimates of how much strain the tires would be under, and as a result how much thermal activity they’d generate.
“When a tire is rotating that fast, the enemy is heat generation,” Schmedding said. “What’s also critical is its acceleration rate above 200 mph, including how long it would take to get from 250 to 260, 270 to 280, et cetera. When we got that information, we developed a test plan to confirm the tires could meet the requirement.”
The team ran tests at Michelin’s aircraft tire testing facility in Charlotte, North Carolina, since the technology there could handle much higher speeds. After running multiple tests, they came back confident the stock rubber could handle the record. Michelin engineers attended the record attempt in Nevada in early November, evaluating the tires between runs to ensure they were holding up in terms of temperature and wear. They were—handily.
“The tires were nowhere near their limits,” Schmedding said.
In addition to the top speed runs for production-vehicle and public-road records, the Agera RS also set a 0-400 km/h record of 33.29 seconds, a flying kilometer record on a public road of 444.76 km/h and a flying mile record of 276.36 mph, with the latter two both being averages of two runs. At the end of the day, the tires had minimal wear, in spite of the tremendous torque generated on the acceleration tests. In fact, the car on display at the auto show still had the same tires on it.
Schmedding said that the biggest factor allowing the Sport Cup 2’s to withstand the stresses isn’t so much compound or tread design, but the construction of the tire itself. An aramid fiber runs around the tire, cinching it together and controlling the growth due to centrifugal force at high speeds. That, in turn, controls the temperature and integrity of the tire.
So how much harder could the tires be pushed—assuming the car itself could also generate enough power and handling to accommodate it? Easily over 300 mph, both Schmedding and Koenigsegg agreed.
“If someone wants to set that record, it’s very doable,” Koenigsegg said. “For the car we would need more RPM and a longer gear ratio, but we could hit 300 right now. It’s scary and very dangerous to drive this fast, because there are a lot of uncontrollable aspects, such as animals, tumbleweeds, bumps, wind. It’s doable, but it’s not our objective.”
So 300 mph is “scary and very dangerous,” but 285 is a walk in the park? Noted.
Schmedding adds that the success of a 300-plus mph run for the tires is also entirely dependent on the car itself. “Heat buildup can run away very quickly at those speeds, and that’s when you’ll run into failure,” he said. “A big part of the equation is how fast you can get there. If the car can get to 270 fairly quickly but it takes five minutes to get from 270 to 300, that’s not really going to work. So for a 300-plus mph run, we’d still want to do some additional validation.”
Ultimately, though, one of the primary roadblocks—so to speak—to cracking 300 mph isn’t the car or the tires, but rather finding a suitably straight and smooth road to do it. Though most assume the Bonneville Salt Flats would be ideal, the surface there is completely different from a paved road and requires specialized wheels and tires. It’s just not the same as blasting down a public road in Nevada….nor probably half as scary.
