Carbon-fiber wheel achieves weight reduction, performance goals for Ford Shelby GT350R

The latest design of the Ford Shelby GT350R comes under a new group within Ford Motor Co. (Dearborn, MI): The Ford Performance group. The group’s goal is to use low-volume, niche vehicles to infuse performance vehicles with cutting edge technology that wins on the road and at the track.

Working with Carbon Rev (CR), a technology company in Victoria, Australia, the Ford Performance group designed a new carbon wheel. Adam Wirth, Ford Performance Chassis Supervisor, presented the details of the design and development of the carbon wheel for the GT350R at the recent Plastics-In-Motion conference in Charleston, SC.

CR is a privately owned company founded in 2007. The company started in a single car garage, then moved to a shearling (sheep shearing) shed at Deakin. CR has been the recipient of various government grants and green car innovation funding, and in 2014 the company moved into a purpose-built facility for the production of carbon-fiber wheels. Today, CR is a Tier One automotive supplier certified to TS 16949 and ISO 9001, employing 100 people and running three shifts a day, six days per week. In 2015, CR was inducted into the Victorian Manufacturing Hall of Fame. The company has two business channels: OEM and aftermarket.

Wirth explained that the carbon-wheel design has a number of benefits, including a low-energy and inherently safer manufacturing process and reduced tooling costs. Reaction injection molding (RIM) tooling provides investment savings compared with alternative low-pressure-casting wheel tooling and a significant savings versus tooling for forged wheels. Additionally, it offers styling flexibility of lightweight designs equal to cast aluminum wheel designs. The significant weight reduction provides reduced shipping costs and infrastructure demands while still meeting stringent wheel stiffness and durability requirements.

“We also realize long tool life,” commented Wirth. “Additionally, the wheel can be manufactured in a room temperature environment compared to a foundry environment, and it gives us unique structures for strength that you can’t get in cast aluminum.”

The weight saving is huge: The carbon wheel weighs approximately 18 pounds compared with an aluminum wheel that weighs around 33 pounds, a weight saving of 60 lbs. per vehicle. Rotational inertia is reduced by 40%, which means faster, more responsive steering and improved acceleration and braking. Increased lateral wheel stiffness means a reduction in steering “dead-band” and a predictable chassis balance. “The result is the most track-capable Mustang every produced,” said Wirth. Car & Driver tested the GT350R wheels in January of this year.

The technology for the one-piece carbon-fiber wheel is created by RTM over pre-formed dry carbon layers, fully infusing the preform during the molding process. Hollow core spokes are designed to provide maximum wheel stiffness—better than aluminum wheels. “The cure time is five minutes for the injection process, which is proprietary, and we have minimum displacement of fibers in the process,” explained Wirth. “It’s a balancing process: Cycle time versus fiber placement.”

Aluminum lug seats and backer plate sandwich the carbon structure to create a robust joint. A proprietary paint system is specific to the carbon substrate to meet or exceed all Ford paint performance requirements. The ultimate focus on quality comes in the form of an embedded RFID chip in the spoke that allows the manufacturing and quality performance history to be tracked. A proprietary resin was required to meet the stringent original equipment requirements: High glass transition temperature, yield stress and elongation, abrasion and weathering resistance.

To meet extreme track conditions, where brake rotor temperatures can reach 900°C continuous, the resin is shielded on the front wheels with a 0.3-mm-thick ceramic heat-barrier material applied using a plasma arc spray, another first-use application. Wheel temperatures are significantly reduced when exposed to the brake heat generated during demanding maximum performance conditions.

Other benefits of the carbon wheel, explained Wirth, are that carbon-fiber wheels significantly improve vehicle refinement with a 50% higher frequency compared to forged aluminum and excellent material damping, 870% higher damping vs forged aluminum. “Superior material, light weight and increased damping result in reduced impact harshness and noise reduction measured at the driver’s ear,” Wirth pointed out. “Hitting a pothole sounds more like a dull thud.”

Another benefit is that cracks and failures are reduced. “The carbon fiber keeps the wheel together and absorbs more of the energy in impacts over aluminum wheels,” said Wirth.

Overall, Wirth noted that the group is trying to reduce cycle time, take the labor toward mechanization and automation. “While the carbon-fiber process is costlier, it’s good for low-volume vehicles.”

Ford expects to be making 50,000 vehicles by 2020.