Ultra-Stiff Caliper designs focused on Dynamic loading

Radi-Cal calipers took a radical new approach to caliper design.  Instead of focusing on stiffness under static (non-spinning) rotors, AP racing modeled how fast spinning rotors torque brakes pads trying to shear the caliper in half.  There is a lot more stress on the rotor than simply trying to spread them a part and symmetrical caliper are not optimized for dynamic brake loading.  Notice the overall Radi-Cal designs below, there is a lot of material and reinforcement in the corners of the caliper supporting the shearing load the brake discs apply to the caliper.  This significantly increases overall caliper stiffness providing improved pedal feel and increased braking torque. 

Maximum Caliper weight reduction & Cooling Airflow

Another visually noticeable Radi-Cal feature is the extreme amount of extra machining around the pistons and reinforcement supports.  Every opportunity to remove weight has been machined away, every gram counts in unspring weight improving the dynamics of the suspension and overall dynamics.  The extra machining provides an additional benefit of increased surface area for heat dissipation.

Hard Anodized Finish

All AP Racing Calipers come with a durable Hard Anodized Finish that provides a consistent look and texture after many hard track days.  Anodization is also chip resistant reducing abrasions or scratches created from tools or wheels while working on your car.  Serious track time exposes calipers to extreme heat and countless thermal cycles that will eventually discolor high temp paint and crack powder coating that cannot expand and contract with aluminum. 

Ventilated Domed Steel Pistons

The main path for heat transfer into the brake fluid is through the caliper pistons.  Brake fluid is providing pressure directly to the pistons that are squeezing the high temperature brake pads.  Stainless Steel has 15X lower coefficient of heat transfer vs aluminum significantly reducing heat transfer into the brake fluid.  Additionally, Radi–Cal calipers have a ventilated face providing air flow inside the piston calipers providing additional cooling. 

Anti-Knock Back Springs

Radi-Cal calipers have an anti-knockback spring that keeps the pistons extended and pads on the rotor during hard corning.   Without anti-knockback springs, you may have to double tap your brakes to extend the pads on the rotor.  Imagine not having expected and immediate torque when applying your brakes after a fast corner! 

72 Vane, 338mm Floating Rotors

We specified our Radi-Cal kit with a lightweight and high cooling 72 Vane, 338 mm CP7472 rotors.  This rotor increases the number of vanes by ~200%over OEM and by 20-100% vs other aftermarket rotors.  The increased vanes move a higher volume of air through the rotors and provide increased surface area significantly improving heat dissipation.  Despite the highest vane count for and S2000 Brake kit, we can keep the overall weight to about the same as the 1-piece OEM rotor and significantly less than other S2000 Big Brake kit rotors.  This kit in combination with our Flow rear rotors can handle 600 HP S2000 track abuse consistently.

Also, the AP Racing CP7472 rotors are mounted on a full floating hat, allowing thermal expansion reducing stress that causes warping and cracks, leading to rotor failure.  Additionally, not all materials are the same and AP Racing discs are cast using a proprietary alloy developed over 50 years of tier 1 racing designed for extreme durability.  Finally, the patented AP Racing J Hook pattern on the rotors amplifies pad feel by maximizing leading edges and distributes surface heat better than straight slots or drilled holes. 

>10 lbs total weight reduction

Each caliper weighs 4.8 lbs vs 10+ lbs for OEM, reducing unsprung weight by nearly ~11 lbs.  The rotors with custom floating hats weigh ~14.5 lbs or about the same as OEM while significantly increasing rotor cooling with ~3X the vane count vs OEM.   The >10 lbs of total weight reduction will improve both handling and acceleration.  Unnecessarily heavier rotors can add significant rotational and unsprung weight reducing acceleration, suspension dynamics and increase effective mass increasing stopping distances. 

Spiegler Lines

Spiegler Brake lines complete the Essex Designed AP Racing Radi-Cal kit.  Spiegler lines are manufactured in quality-controlled facilities across the US & Europe.  The connoting banjos use a stress-free torsion fitting system to ensure that improves alignment with caliper and brake plumbing.  Spiegler lines use a DuPont Teflon inner lining and a heavier gauge stainless steel braid reducing line flex and improving brake feel.  The braids are wrapped in an abrasion resistant coating to reduce potential snags or damages to the lines. 

Confirmed Clearance 

17×9.5 +41 Volk EVS spec TE37 

AP Racing Radical CP9441 Pad Shapes 

• Alcon PNF0084X276.4
• AP Racing CP3215D42 (42 mm pad depth)
• Project Mu F1076-3
• Carbotech CTCP9449
• Cobalt AP13
• PFC 7768.XX.16
• CL Brakes 5004W42T17
• Ferodo FRP3018
• Endless RCP074
• Pagid 2126
• Hawk HB718.654 

Wheel Template

How to check brake kit clearance