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Photo Credit: ESE Carbon Co.

(ESE, Miami, Fla., U.S.) recently launched its E2 one-piece carbon fiber composite wheels into the market for the aftermarket segment. The initial E2 launch includes 19 x 8.5-inch wheels, servicing Tesla Model S, Tesla Model 3 and Subaru WRX STI vehicles.

The wheels, which CW wrote about in 2020, use tailored fiber placement (TFP) and high-pressure resin molding (RTM) to produce a lightweight, single-piece, high-performance wheel. Since CW last wrote about the wheels, ESE has completed its transition from initial autoclave processing to an improved RTM process using heated tooling. The resin and tooling are said to be preheated, with carefully controlled resin flow during infusion. Improvements have also been made to the TFP stitching process, to improve productivity as well as wheel mechanical properties. Small ply changes have been made to the E2s to ready them for market, to improve layup consistency, appearance and wheel test performance, and a clear coat solution has been finalized. The mounting hardware has also been refined to improve lug torque retention.

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The wheels have been a four-year process to develop and test, ultimately passing stringent fatigue and impact tests set by the Society of Automotive Engineers’ (SAE) Recommended Practices for wheels.

According to ESE and , SAE recommended practices such as SAE J328 for vehicle wheels, SAE J2530 for aftermarket wheels, SAE J2562 for biaxial wheels, and SAE J175 for road vehicle wheels were originally designed to test traditional metal wheels. The E2s were able to pass all tests required of SAE, due to the wheels’ rigorous engineering analysis and testing during development, the company says.

Dr. Michael Hayes, ESE Carbon’s VP, head of engineering, served on an SAE committee in 2020 to develop new recommended practices specific to fiber-reinforced composite wheels.

Photo Credit: ESE Carbon Co.

The resulting SAE J3204 adapts the Recommended Practices for metal wheels to composite wheels, imposing new requirements such as strength reduction factors (SRFs) to account for environmental effects, maximum operating temperature testing, and electricity conductivity testing. 

ESE emphasizes that its E2 wheels have also been proven to withstand impact at very cold temperatures, above and beyond the requirements. The company conducted its own independent lab testing to test curb and pothole impact at -40°C. The company says its wheels were not affected by the cold temperatures at all, thanks to specially developed wheel flanges designed with a high percentage of circumferentially oriented carbon fiber to maximize hoop strength. This strength is said to be great enough to enable the circumferential plies to be “nearly insensitive” to cold temperatures. “We have taken great care to design very robust flanges in our wheels,” Dr. Hayes explains. “In addition, because of the superior strength-to-weight ratio of carbon fiber composites, we can increase the size of the flanges to further increase impact strength without a weight penalty.” The TFP process allows for production of circular plies at a high fiber volume fraction.

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