You might have noticed that car wheels have gotten pretty large over the last few years. Designers love putting hefty wheels on cars, particularly big trucks and SUVs, because they help make big vehicles look smaller. Expect the trend to stick around as electric vehicles proliferate—big wheels are particularly effective at helping hide the extra height of the slab of lithium-ion cells between the axles.
The trouble is, big wheels might look good, but that aesthetic comes with a cost. A larger wheel is heavier, and it’s the very worst place to add pounds if you’re concerned about handling, since it is unsprung mass. This is why some wheels are made out of aluminum alloy instead of pressed steel, but even aluminum wheels weigh a lot if they’re 22 inches in diameter—or bigger.
Enter Carbon Revolution and its carbon-fiber wheels, stage left.
Originally a plaything of the aerospace industry, carbon-fiber composites first caught the eye of the automotive industry via racing. Extra weight is the enemy of a good lap time, and F1 designer John Barnard realized that he could build cars that were at least as strong as those made from steel and aluminum, but far lighter. Initial safety fears from naysayers proved unfounded, and for several decades, carbon fiber has been the material of choice for prototype and single-seat race cars.
Carbon fiber isn’t quite as commonplace in road cars, but it’s there if you know where to look. Plenty of hypercars boast carbon-fiber chassis tubs, and you’ll find body panels made of the stuff in some performance cars.
It took longer for someone to make wheels out of carbon fiber, but that, too, first happened in the crucible of racing. But not Formula 1—in this case, the breakthrough actually happened in a Formula SAE team at Deakin University in Australia. In 2004, Ashley Denmead and his teammates were looking for a way to take a lot of mass out of their car, which the year before had weighed a hefty (for Formula SAE) 750 lbs (340 kg).
Cutting unsprung mass in particular was critical. “That led us to recognizing pretty early on that the wheels that you can buy for these cars were really not appropriate for the vehicles,” Denmead explained. “Nobody makes a wheel suitable for a 200 kg [440 lbs] car. The wheels of the size we were running are suitable for, you know, 1,200 kg [2,646 lbs] cars. So we thought we should try and make our own wheels, which sounded like a good idea at the time.”
The design was refined over the next few years’ competitions, until Carbon Revolution (originally known as C Fusion) was founded in 2007 when Denmead—Carbon Revolution’s engineering director—and his colleagues graduated.
The original Formula SAE wheels were made by hand, with brushed-on resin. Today, Carbon Revolution uses a resin-transfer molding process, which we’ve seen used by companies like McLaren and Lamborghini for body panels and even chassis tubs.
“There’s a lot of automation of dry fiber, both cutting, preforming, assembling those dry fiber preforms together with robots, winding the rim with dry fabric off a roll, and then the tools come together, and we inject the resin through the fiber,” Denmead told me. “And we can have full control over the resin system, full control over the cure, and full control over the dry fabrics and fibers that we purchase and specified.”
So far, Carbon Revolution’s wheels have mostly graced high-end performance cars. The wheels have been fitted as original equipment to some Ferraris, as well as the Ford GT500 and Chevrolet’s forthcoming Corvette Z06. For track-biased machines such as those, lighter wheels equate to sharper handling and therefore faster lap times. But for an EV, the goal is more range.
A wheel’s aerodynamics are actually much more important than its weight when considering EV applications. “We can have unique wheel designs that are very aerodynamic front faces that are quite closed without being really heavy,” Denmead told me.
“If you do those designs in metals, you generally get, really, a heavy wheel, because they’ve got minimum thicknesses,” he said. “And if they’re casting those wheels, you can’t have thin features, because you get cold shots and things like that. Whereas obviously with carbon-fiber manufacturing, you can have very thin shells if you like or very thin features that are just like wings on a wheel that have no real structural integrity behind them, and you get the aerodynamic performance you want.”
An added benefit is that carbon wheels don’t transmit as much noise as their metal counterparts, so the overall driving experience is quieter—again, something you notice in an EV.
Specifically, Carbon Revolution says a carbon-fiber EV wheel could increase efficiency by around 5 percent as well as cutting noise by around 5 decibels. And the weight saving is significant—a 19-inch carbon-fiber wheel might weigh 31 lbs (14 kg) versus 66 lbs (30 kg) for a similar-sized alloy wheel. The wheels are not especially cheap, although Denmead said that they’ve achieved price parity with the most expensive forged wheels.
Carbon Revolution has been working with OEM partners on EV-specific wheels for a while now, although contracts prevent the company from revealing those OEMs until they make their formal product announcements. I’m definitely curious to find out who they are.