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.

Fast Pad Changes

Notice how AP Racing calipers have a few top bolts that can be removed so pads can slide in and out without removing the caliper.  Pad changes can happen in minutes vs tens of minutes.

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 significantly lower coefficient of heat transfer vs aluminum 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!

High Vane count Floating Rotors

Essex uses 72-84 vane rotors in their Porsche GT front brake kits and 60-72 vane rotors on their Porsche GT rear brake kits.  Higher vane counts move a higher volume of air through the rotors and provide increased surface area significantly improving heat dissipation.  Higher vane counts also improve rotor structural rigidity reducing coning, distortion and cracking.

AP Racing Proprietary Metallurgy

Not all materials are the same and AP Racing discs are cast using a proprietary alloy developed over 50 years of tier 1 racing in Formula 1, NASCAR and Rally Car.  AP Racing iron alloy improve durability over competitive steel alloys.

Patented AP Racking J-Hooks

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.  Cross drilled rotors are typically stress risers that lead to cracks.

Spiegler Lines

Spiegler Brake lines complete the Essex Designed AP Racing Radi-Cal Kits.  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.