The Future of Carbon-Fiber Rims

Way back in the early 1970s, Michelin made a run of composite glass-fiber and resin wheels for Citroën’s SM-based rally car. The first car equipped with them won its first race, the 1971 Morocco Rally. By 1972 they were offered as a factory option for buyers of road-going SMs.

In the 1980s, Dodge and Carroll Shelby teamed up for the CSX, the final version of which, the 1989 CSX-VNT, wore a set of composite wheels called Fiberrides. Like the Michelin/Citroën wheels before them, the Fiberrides were a composite glass fiber construction.

Fast-forward to 2013, when boutique hypercar maker Koenigsegg began offering carbon-fiber one-piece wheels for its 250-plus-mph ground-bound spaceships. They’re quite a pretty penny, however: A set of four will set you back about $40,000—on top of the roughly $2 million price tag for one of its cars.

Carbon fiber’s ability to tolerate a wide range of temperatures without becoming brittle or deformable depends not on the carbon itself but on the epoxy that surrounds it.

Today, Porsche is the only mainstream automaker developing one-piece carbon-fiber wheels in-house, and there’s just one supplier, Carbon Revolution, manufacturing them for production cars, including the Ford GT, Mustang GT350R, and several upcoming models from other brands—though there are a number of other outfits making “hybrid” carbon/alloy wheels for the aftermarket. Carbon Revolution has big plans to scale up from the tens of thousands of one-piece carbon-fiber wheels it says it will produce this year into the hundreds of thousands if not millions as it moves into the next decade. Sooner if co-founder Brett Gass has his way.

“We’ve got a program underway that’s a 22-inch carbon-fiber wheel for a very serious off-road SUV,” Gass said. “And those types of volumes in that world, those are tens of thousands of vehicles. Those are big programs.”

Carbon Revolution is also working with Ferrari on wheels for the 488 Pista, as editor-in-chief Mike Floyd learned at this year’s Geneva auto show. “We were very demanding with the style,” Edoardo Rossi, Ferrari product marketing manager for the 488 Pista, said of Ferrari’s work with Carbon Revolution to develop the Pista’s special wheel option. “The spokes are not huge spokes that you see in normal carbon-fiber components. They are very thin, so it was an adjustment. Then we developed together the solution that you see inside, the white coating. It is basically a coating developed from aerospace to preserve the carbon wheel from the heating of the brakes.”

The Advantage

Although lighter weight is the primary benefit of a composite wheel—particularly a carbon-fiber one—there are also advantages to be gained in the noise, vibration, and harshness arena. Metal wheels, including steel and aluminum, transmit a great deal of high-frequency NVH from the road through the suspension and into the car’s structure. Carbon-fiber wheels damp that energy better, cutting it out of the equation where it begins. As a result, carmakers will be able to engineer quieter cabins without having to add pounds and pounds of sound insulation.

“Not only the light weight and the stiffness, but the damping characteristics really just get rid of that high-frequency [vibration], particularly in the luxury electric vehicle space, where you don’t have powertrain and exhaust noise and all those other things,” Gass explained.

Lighter wheels improve acceleration and dece-leration, as the engine and brakes no longer need to work against as much rotating mass. They also reduce gyroscopic effects, making initial turning behavior more sensitive and controlled, and the amount of unsprung weight at each corner—the byproducts of which are improved ride comfort and more desirable handling characteristics thanks to a lessening of the suspension’s overall workload.

Every aspect of the carbon wheel that aids per-formance also benefits efficiency for the same reason—physics: You’re able to do the same or more with less energy. The only difference is the goal. Rather than chasing terminal velocity and optimum lap times, lightweighting a hybrid or electric car helps to maximize its range. With less mass in the wheel to be spun up to speed and then dragged back down, there’s less energy going to waste every time the car speeds up or slows down, which can mean miles (or tens of miles) more to a charge or a tank.

The “But”

So carbon-fiber wheels can unlock greater performance potential, improve efficiency, and enhance comfort and quietness. They seem like the perfect solution, so why all the fear, uncertainty, and doubt? Two reasons: price and myths.

A set of Carbon Revolution’s aftermarket wheels will run you about $12,000. Although that’s competitive with the very top end of the custom forged alloy wheel aftermarket, there’s no $1,000-a-set option as yet in the carbon-fiber space. But that will change over time as volume—and eventually competition—increases.

“Today we’re not really a disruptive technology,” Gass said. “We’re too expensive, too exotic. When we get to gen three of the technology where we’re cost competitive with forgings and superior in every product attribute, now you’re disruptive. Now you’re a real threat to a good chunk of the aluminum market. We’re not far off. We’re one generation of production away from that, which could show up on the road in the next two to three years.”

What Gass calls the “rarest automotive light-weighting technology in existence” today (he claims there are more suppliers for the LaFerrari KERS hybrid system than for one-piece carbon-fiber wheels) could conceivably become ubiquitous within the next decade, wheels that not just supercars but potentially every car will roll on. But that will only happen if the mythmongers are proven wrong.

The Myths

Carbon is fragile! Carbon shatters! You can’t repair it! Carbon wheels will melt when they’re hot! They’ll crack when they’re cold! They leak air!

The litany of fake news fatal flaws of the carbon-fiber wheel is not quite endless, but it’s certainly extensive. And none of it is true—at least if the wheel is made correctly. The seed of the myths was planted by a handful of aftermarket wheels, most of them two- or three-piece “hybrids” (carbon barrels with alloy hubs and spokes), none of them tested to OEM standards for road use. They’re very different creations from the fully tested one-piece wheels from Porsche, Koenigsegg, and Carbon Revolution.

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What makes a wheel true?...