Deep within the top-secret engineering groups responsible for the now-declassified ’14 Corvette Stingray, men and women whispered of the existence of a new option group addressing various aspects of vehicle performance, from aerodynamics to braking.
Sanluis Rassini's patented dual-cast rotor makes its debut in the Z51 Performance Package
As we learned in January at the car’s unveiling, that package will carry the long-running Z51 designation and be available on the reanimated Stingray when it goes on sale later this year. One of its more notable components is a unique patented brake rotor, which will replace the J55 cross-drilled units previously offered on the ’11-’13 models.
This new rotor features a combination of ductile and cast iron, which provides a weight savings of up to 18 percent as compared with the C6’s standard single-piece rotors. The design also improves the C7 braking system’s heat-management attributes, giving the sports car reliable and consistent stopping power.
The rotors are manufactured by Sanluis Rassini, the world’s largest producer of suspension components for light commercial vehicles, and the largest fully integrated brake-disc producer in the Americas. Its relationship with General Motors dates back to 1982, and its components are already on Chevy’s Equinox and Tahoe, GM trucks, and other GM models.
“One of the reasons we’re able to develop advanced technology such as this is, we’re the only vertically integrated rotor-manufacturing center in the Americas…This technology was developed for high-performance vehicles like the 2014 Corvette, [which] require better heat-transfer capabilities at lighter weights,” says Sanluis Rassini Chief Executive Officer Eugenio Madero.
Sanluis Rassini Engineering Director Mauricio Gonzalez put the brakes on his daily duties long enough to discuss the Z51 Performance Package’s new rotors with us. Here’s what he had to say:
Thanks to those once-classified computer-aided design (CAD) images, we can show you the fr
This image shows the rotor early in the process, with the sand core in place
Here's the as-cast-gray-iron braking surface before machining.
VETTE magazine: Did Chevrolet approach you with the idea for the rotor?
Mauricio Gonzalez: No. For the 2014 Corvette, GM had very aggressive weight and performance targets, which were not achievable with a one-piece-casting rotor. [At] around that time we finished the development and testing of the concept design for the rotor, and we were able to offer it to GM as a solution.
VM: Is the rotor a clean-sheet design?
MG: Yes, it is the industry’s first ever to include a ductile-iron hat and gray-iron brake plates.
VM: Is the rotor a traditional solid-extension design?
The final CAD image shows a fully machined front-rotor assembly.
MG: No. This new rotor features an I-beam extension design. The connection between the hat and the braking surface is called the I-beam, and it increases the amount of air entering the vent area. “I-beam” refers to the cross-sectional shape of the extension as viewed from above. In this case, the body of the I is oriented in the circumferential direction—in other words, parallel to the brake plates.
This body maintains the structural integrity of the extension. Small fins extend perpendicular from this body to the interior of each brake plate, thereby completing the shape of a capital I.
VM: What is the primary benefit of the rotor’s design?
MG: It allows for a significant weight reduction, which translates into a boost in fuel efficiency, something that’s extremely important to [General Motors]. Also, this rotor is 30 percent less expensive to manufacture than comparable aluminum-composite rotors.
VM: What other features make the rotor unique?
MG: It is the only composite rotor on the market that accommodates a drum-in-hat, or DIH, for the rear axle. [This is a] design in which the internal surface of the hat serves as a brake drum [for the parking-brake system]. The rotor features a unique design on the joint between the hat and braking surfaces, which reduces roughness due to uneven hardness…on the surface.
VM: How does it differ from the J55 cross-drilled rotors offered optionally on ’11-’13 Corvettes?
MG: In previous generations, GM offered a full-cast rotor design for most packages, and a carbon-composite material as option J55. This new Z51 rotor works as a floating rotor at high temperatures, and as a full-cast rotor at low temperatures, in both cases with no thermal transient deformation.
VM: Please describe the heat-management process, and compare it with the previous design.
MG: Most brake rotors have inboard or outboard ventilation. This rotor features inboard and outboard ventilation, [which has] a positive effect on the cooling rate of the system. This creates the best heat-transfer coefficient between the cooling air and the cast iron. The post fins are designed to work at both low and high speeds.
VM: Compared with previous OE rotors, how does this one hold up against warping, wear, and rust?
MG: The joint between the hat and braking surfaces [features] a unique design to avoid roughness and improve cooling in the joint area. But Rassini took it a step further and released all the internal stress from the part to avoid warping caused by extreme temperatures and abuse. These rotors also use the latest coating technology to avoid corrosion on non-rubbing areas.
…while the rear rotor measures 13.3 inches across. It also features an innovative drum-in-
The Z51 front rotor features a 13.6-inch diameter…
VM: Where is the rotor manufactured?
MG: It’s manufactured at Sanluis Rassini’s fully integrated brake-rotor facility in Puebla, Mexico, which features an integrated foundry and machining, coating, stress-relief, and ferritic nitrocarburizing processes.