To source the new lightweight track-capable carbon fiber wheels that are standard on the new Shelby GT350R Mustang, Ford partnered with Australia-based Carbon Revolution. Carbon Revolution first began delivering composite wheels in 2004 for Formula SAE campaigns. The company now is producing its “CR-9” wheel series in limited numbers for Porsche, BMW M3, Audi R8, Lamborghini and McLaren MP4-12C within Europe, Japan and North America. Ford, however, wanted more of a mass-production solution.
The one-piece carbon fiber wheels for the Mustang weigh nearly half that of an equivalent aluminum wheel (18 pounds versus 33 pounds), and handling and acceleration performance see serious benefits. The wheels also provide a reduction in rotational inertia of more than 40%, which positively impacts acceleration and braking performance. The wheels are so light, the springs and MagneRide dampers had to be recalibrated because the suspension can respond considerably faster to road inputs.
In early testing with benchmark vehicles, prototype wheels showed significant potential—improving suspension response times, chassis dynamics, steering feel and ride quality. When the decision was made to pursue this technology for use in a production vehicle, the engineering team was challenged to develop a wheel that met Ford’s standards for durability, quality, craftsmanship and premium finish.
Lowering overall curb weight in general is beneficial to a car’s dynamics, but a reduction in unsprung weight (those components not supported by the suspension) can have a significant impact on handling and performance. Less unsprung weight helps vehicles start, stop and turn faster by reducing wheel rotational inertia, significantly improving response time to driver input. Lower unsprung weight also results in suspension components not having to work so hard to keep the tires in contact with the road over undulating or broken surfaces.
Although Carbon Revolution has been the leading manufacturer of carbon fiber wheels, both Ford and the supplier recognized significant innovation was needed to meet Shelby GT350R program needs.
Ford wheels must endure tests that include curb strikes, UV and chemical exposure, and extreme heat durability testing. The GT350R wheels would need to fulfill all of these demands in order to proceed to production.
A common misconception of carbon fiber is that while it’s strong, it’s also a brittle material. Some formulations may have this characteristic, but carbon fiber’s durability is a feature of the type of resin and design intent of the part. The wheels of Shelby GT350R are designed to be stiff, light and resilient.
One of the most severe tests for wheels in the Ford development process involves striking a curb at speed— a test that, without proper design, can cause serious wheel and tire damage. Because of the light weight, advanced construction methods and resins in the wheels, along with the highly-developed MagneRide dampers, the suspension was able to react so fast that the driver wasn’t sure the test had been carried out correctly and ran it twice to be sure. The suspension response was fast enough to greatly diminish the severity of the impact.
During track testing the extreme performance capabilities of the braking system developed heat which required the maximum technology available from Carbon Revolution. Shelby GT350R’s ultra-powerful brakes were creating rotor temperatures in excess of 900 degrees Celsius. As a result, the wheel design was elevated from a road car specification to a thermal standard more suitable for motorsports.
For decades aerospace companies have treated turbine blade materials subject to extreme heat with ceramic coatings to help improve durability. The technology is also used in top-tier open-wheel racing environments. A thermal barrier coating system developed by Carbon Revolution uses this same technology.
Created specifically for motorsport and aerospace applications where extreme temperature conditions are encountered, Carbon Revolution’s thermal barrier coating system uses a multistage, multimaterial coating formulation that provides an excellent thermal barrier. Using a plasma arc gun to liquefy a ceramic material, the wheels are coated at critical points around the inner wheel “barrel” and on the back of the spokes. The result is a thin, nearly diamond-hard coating that reliably shields the resin from heat—reducing maximum wheel temperatures and allowing continuous track use by even the most aggressive drivers.
Upon extreme exposure to harsh UV environments, corrosive salts and road chemicals, it became apparent that to achieve the durability required by Ford, a special coating would need to be developed to protect the resin from the environment.
Carbon fiber parts are challenging when it comes to delivering a flawlessly smooth painted surface. Several proprietary new processes were developed that resulted in a robust, high-gloss black finish that not only looks good, but ensures a long life for the wheels.
Manufacturing carbon fiber wheels begins with the creation of the preformed internal carbon structure, composed of precisely manufactured carbon strands arrayed into woven fabrics. The elements are then placed into a mold using advanced manufacturing techniques.
An RFID chip with a unique tracking number is embedded in this structure, and each wheel is individually entered into a quality assurance system. Once this structure is assembled, it’s infused with resin and cured at high temperatures.
This process results in a one-piece wheel that ensures maximum strength—eliminating the need to bond or glue the wheel’s spokes and barrel components together.
As the wheel cures, 61 individual checks and more than 246,000 data points are logged before it’s released from the machine. To guarantee quality parts, the cured wheels are analyzed using a 3D computerized tomography (CT) imaging process in which more than 18,000 X-ray images are taken.
If the wheel passes inspection, it undergoes machining for the valve stem and mounting hardware holes before it gets painted, coated, assembled, dimensionally checked and shipped to Flat Rock Assembly Plant for installation on a new Shelby GT350R Mustang.