Ultra-Stiff Caliper designs focused on Dynamic loading

Radi-Cal calipers represent a revolutionary advancement in caliper design. Unlike traditional calipers, which prioritize stiffness under non-spinning conditions, Radi-Cal calipers have been developed to withstand the shearing forces generated by fast-spinning rotors. By taking into account the stresses on the rotor and the brake pads, AP Racing has designed a caliper that is optimized for dynamic brake loading, providing superior performance and enhanced braking torque.

One notable feature of the Radi-Cal caliper is its asymmetrical design. Rather than being symmetrical, the caliper is reinforced in the corners to support the shearing load generated by the brake discs. This significantly increases overall caliper stiffness, resulting in improved pedal feel and increased braking torque.

The Radi-Cal design is a prime example of how a new approach to traditional problems can yield impressive results. With its superior performance, Radi-Cal represents a significant step forward in caliper technology, providing discerning racers and enthusiasts with the ultimate in braking power and control.

Maximum Caliper weight reduction & Cooling Airflow

The Radi-Cal calipers are not only designed to handle dynamic brake loading but also aim to minimize unsprung weight. This is achieved by machining away any excess material around the pistons and reinforcement supports, which significantly reduces the overall weight of the caliper. The reduced unsprung weight helps improve the suspension dynamics of the vehicle, leading to better handling and performance. Additionally, the extra machining increases the surface area of the caliper, facilitating better heat dissipation, which is a crucial aspect of high-performance brake systems.

Hard Anodized Finish

AP Racing Calipers are built with a durable Hard Anodized Finish that provides a uniform look and texture after numerous hard track days. Anodization also enhances chip resistance, reducing abrasions or scratches caused by tools or wheels while working on the vehicle. Serious track time exposes calipers to extreme heat and countless thermal cycles that eventually discolor high-temperature paint and crack powder coating that cannot expand and contract with aluminum. With the Hard Anodized Finish, AP Racing Calipers can withstand high temperatures and thermal cycles while maintaining their appearance and structural integrity.

Ventilated Domed Steel Pistons

As heat is a primary issue in brake system performance, the URGE Essex brake kit features Radi-Cal calipers, which adopt an innovative approach to caliper design. Unlike traditional calipers that prioritize stiffness under static rotors, Radi-Cal calipers factor in the torque that fast spinning rotors apply to brake pads, which can cause them to shear the caliper in half. As such, Radi-Cal calipers feature an asymmetrical design that includes reinforcement in the corners to support the shearing load brake discs apply to the caliper. This increased stiffness significantly improves pedal feel and increases braking torque.

In addition to the asymmetrical design, Radi-Cal calipers feature an extreme amount of extra machining around the pistons and reinforcement supports, which reduces unsprung weight, improving the dynamics of the suspension and overall performance. The extra machining also increases surface area for heat dissipation, an essential factor in maintaining brake system performance over long track days.

Moreover, all AP Racing Calipers in the URGE Essex brake kit come with a durable hard-anodized finish that provides a consistent look and texture even after many hard track days. The anodization is chip-resistant, reducing abrasions or scratches created from tools or wheels while working on your car, making them a perfect choice for discerning track day aficionados and club-level racers.

Furthermore, heat transfer into the brake fluid primarily occurs through the caliper pistons. With Radi-Cal calipers’ stainless-steel construction, the coefficient of heat transfer is 15 times lower than aluminum, significantly reducing heat transfer into the brake fluid. Additionally, Radi-Cal calipers feature a ventilated face that provides air flow inside the piston calipers, providing additional cooling.

Anti-Knock Back Springs

Radi-Cal calipers feature an anti-knockback spring mechanism, which maintains the pistons extended and the pads in contact with the rotor during hard cornering. The absence of this feature could require the driver to apply brakes twice to remount the pads on the rotor, resulting in a potential delay in brake torque when needed the most.

72 Vane, 338mm Floating Rotors

Our URGE Radi-Cal kit features a lightweight and high-cooling 72 vane, 340mm CP7472 rotors, carefully selected to meet the demands of high-performance track use. The rotor design significantly improves heat dissipation due to increased vanes, which move a higher volume of air through the rotors and provide more surface area. Despite having the highest vane count among S2000 brake kits, our kit is still lightweight and only slightly heavier than the OEM 1-piece rotor, significantly lighter than other S2000 big brake kit rotors. This combination with our Flow rear rotors can handle up to 600 HP S2000 track abuse.

Furthermore, the AP Racing CP7472 rotors use a full-floating hat, allowing thermal expansion to reduce stress that causes warping and cracks, preventing rotor failure. The proprietary alloy used in the AP Racing discs is developed over 50 years of tier 1 racing to provide extreme durability. Additionally, the patented AP Racing J Hook pattern on the rotors maximizes leading edges, amplifying pad feel and distributing surface heat more effectively than straight slots or drilled holes.

Investing in our URGE Radi-Cal kit ensures maximum performance and durability, even under the most demanding track conditions.

>10 lbs total weight reduction

Each Radi-Cal caliper weighs only 4.8 lbs, which is significantly lighter than the OEM caliper that weighs over 10 lbs, reducing the unsprung weight of the vehicle by nearly 11 lbs. The custom floating hats used in combination with the 340mm CP7472 rotors weigh about the same as the OEM rotors, but have over three times the vane count, which increases rotor cooling and thermal capacity. The total weight reduction of more than 10 lbs improves both handling and acceleration of the vehicle. Heavy rotors can add significant rotational and unsprung weight, which can reduce acceleration, suspension dynamics, and increase stopping distances.

Spiegler Lines

The Essex Designed AP Racing Radi-Cal Kits are completed with Spiegler Brake lines. Spiegler lines are manufactured in quality-controlled facilities across the US and Europe. The connecting banjos use a stress-free torsion fitting system that improves alignment with the caliper and brake plumbing. Spiegler lines use a DuPont Teflon inner lining and a heavier gauge stainless steel braid that reduces line flex and improves brake feel. The braids are wrapped in an abrasion-resistant coating to reduce potential snags or damages to the lines, ensuring their durability and longevity.

AP Racing Radical CP9441 Pad Shapes

• AP Racing CP3215D50 (50 mm pad depth)
• Project MuF1076 (We stock HC+ and Club Racers)
• CarbotechCTCP2279PFC7767
• CL Brakes5004W50T17
• FerodoFRP216
• EndlessRCP015
• Pagid1361
• HawkHB110

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