AP Racing by Essex Radi-CAL Competition Brake Kit (Front CP9668/390mm D62) – S550 S650 Mustang GT & Dark Horse
AP Racing by Essex Radi-CAL Heavy-Duty Competition Brake Kit (Front CP9668/390mm D62)
The ultimate heavy-duty front brake upgrade for the S650 Dark Horse, S650 GT, and S550 Mustang. Featuring AP Racing CP9668 six-piston Radi-CAL calipers in hard anodized finish paired with 390x36mm 72-vane J Hook floating racing discs, this D62 kit saves approximately 25 lbs of unsprung weight versus OE Dark Horse brakes.
Complete kit includes calipers, discs with 6061 aluminum hats, mounting brackets, Spiegler stainless steel brake lines, and installation instructions. Clears OE 19×10.5" Dark Horse Handling Pack wheels without a spacer. Uses D62 heavy-duty pads (62mm radial depth) for maximum thermal capacity and fade resistance.
SKU: 13.01.10211 • Application: Track/Competition • Fitment: S650 Dark Horse & GT, S550 Mustang
AP Racing by Essex
Radi-CAL Heavy-Duty Competition Brake Kit Front CP9668/390mm D62
The ultimate front brake kit for the S650 and S550 Mustang. Essex-designed D62 radial-depth pads deliver extra thermal capacity, longevity, and fade resistance for heavy-duty track competition.
Heavy-Duty Competition
Heavy-Duty Competition Braking for the S650 & S550 Mustang
This kit centers on the Essex-designed D62 radial-depth pad, delivering substantially greater thermal mass, longevity, and fade resistance compared to standard D54 kits. Built for drivers who demand the most from extended track sessions, endurance events, and high-heat competition use.
The CP9668/390mm front kit saves approximately 25 lbs of unsprung weight on the front axle versus the OE Dark Horse brakes. It clears the OE 19×10.5″ ET24 Dark Horse Handling Pack wheel without a spacer, making it a direct upgrade with no wheel changes required.
This kit uses Ferodo Racing D62 pads exclusively. All four Ferodo compounds are available: DS3.12, DSUNO, DS1.11, and DS2500. For a complete, balanced brake system, pair it with the CP9451/365mm rear kit.
Key Advantages
Engineered Without Compromise
Eight reasons this kit dominates heavy-duty track competition
Radi-CAL Design
AP Racing’s patented asymmetric caliper architecture delivers 30%+ greater stiffness than conventional designs while reducing weight and improving airflow.
Hard Anodized Finish
Hard anodizing creates an extremely hard aluminum oxide layer via electrical current through an acid bath. Far more durable than paint or powder coat at track temperatures. Will not chip, flake, or degrade under sustained heat.
D62 Heavy-Duty Pads
62mm radial depth pads provide substantially greater thermal mass and heat capacity than standard D54 pads, delivering improved fade resistance and significantly longer life under sustained hard braking.
25 lbs Lighter
Saves approximately 25 lbs of unsprung weight on the front axle versus OE Dark Horse brakes. Less unsprung mass means faster response, better grip, and reduced fatigue on suspension components.
72-Vane J Hook Discs
Superior airflow and heat evacuation versus the OEM 60-vane design. J Hook slot pattern creates uniform heat distribution with more leading edges for consistent bite.
Stainless Steel Pistons
Ventilated, domed-back stainless steel pistons (not aluminum) provide a superior thermal barrier, keeping heat out of the brake fluid and maintaining firm pedal feel through long sessions.
Anti-Knockback Springs
Maintain piston position through corners, eliminating the pedal drop common with fixed calipers during aggressive cornering and disc knockback.
Spiegler Brake Lines
DOT-compliant stainless steel brake lines with lifetime warranty included in every kit. Improved pedal feel with abrasion-resistant coating for long-term durability.
Complete Kit
What’s In The Box
-
AP Racing CP9668 Radi-CAL Pro5000R Calipers (Pair)6-piston, 6.9 lbs each (no pads) — hard anodized finish with ventilated domed-back stainless steel pistons and anti-knockback springs
-
AP Racing 390x36mm J Hook Racing Discs (Pair)72 directional vanes — 2-piece fully floating bobbin drive with 6061 hard-anodized aluminum hats and attachment hardware
-
Caliper Mounting Brackets & HardwarePrecision-machined brackets with aircraft-quality mounting hardware
-
Spiegler Stainless Steel Brake Lines (Pair)DOT-approved with abrasion-resistant coating and lifetime warranty
-
Detailed Installation InstructionsStep-by-step guide for proper fitment and torque specifications
-
Quick-Change Spring ClipAlternate pad retention system for faster trackside pad changes
-
Not Included: Brake PadsFerodo Racing D62 pads sold separately — DS3.12, DSUNO, DS1.11, or DS2500 ($250 each)
-
Not Included: Pad Tension ClipsOptional add-on for additional pad retention
Technical Data
Specifications
Caliper (CP9668)
6-Piston Radi-CAL Pro5000R
Disc (390x36mm)
72-Vane J Hook Racing Disc
Engineering
Technology Deep-Dive
Radi-CAL Technology
AP Racing’s patented asymmetric caliper design, developed using advanced CAD and FEA analysis. During braking, massive tangential friction force pulls the caliper in the disc rotation direction (parallelogram effect). The Radi-CAL design distributes body mass diagonally to oppose this force.
The result: 30%+ more stiffness, less weight, better airflow around the disc, and superior packaging compared to conventional symmetric calipers.
Hard Anodized Finish
Paint and powder coat degrade under sustained track heat. Hard anodizing passes electrical current through the aluminum caliper body in an acid bath, growing an extremely hard aluminum oxide layer directly from the base material. The result is an integral protective surface that cannot chip, flake, or separate.
Hard anodized surfaces are significantly harder than the base aluminum and provide excellent corrosion resistance, thermal stability, and abrasion protection through thousands of track miles.
D62 Heavy-Duty Pads
Standard competition kits use D54 pads with 54mm radial depth. This heavy-duty kit uses D62 pads with 62mm radial depth for substantially greater thermal mass, higher heat capacity, improved fade resistance, and longer pad life.
D62 pads are mandatory on track. Using D54 or D51 pads leaves an unswept ring on the disc face that creates a thermal gradient and causes disc cracking under heavy use.
Stainless Steel Pistons
Ventilated, domed-back stainless steel construction (not aluminum). Stainless steel provides a superior thermal barrier that keeps heat out of the brake fluid, maintaining consistent pedal feel through extended sessions.
The domed back adds structural stiffness under load. Ventilation gaps between pistons promote cooling airflow, further reducing operating temperatures.
Two-Piece Floating Discs
One-piece discs cone when heated unevenly — the center heats faster than the outer edge, causing the disc to warp. Two-piece floating design uses oblong hat mounting holes that allow radial expansion without distortion.
The floating bobbin drive system accommodates thermal growth, reducing stress cracks, pad taper wear, and the vibration that comes from distorted one-piece discs.
J Hook Slot Pattern
Straight slots create localized cool spots and stress risers that can lead to cracking. AP Racing’s J Hook pattern creates a constant pathway of evenly distorted material across the entire disc face.
The result is uniform heat distribution, cleaner pad transfer film, and more leading edges per rotation for consistent bite from the first lap to the last.
How It Compares
Essex/AP Racing vs. OE Dark Horse
| Specification | Essex CP9668 | OE Dark Horse (Brembo) |
|---|---|---|
| Weight (no pads) | 6.9 lbs 57% Lighter | 15.9 lbs |
| Pad Thickness | 25mm 67% Thicker | 15mm |
| Design | Radi-CAL Asymmetric | Conventional |
| Finish | Hard Anodized Track Grade | Paint |
| Specification | Essex/AP Disc | OE Dark Horse |
|---|---|---|
| Type | 2-Piece Floating Superior | 2-Piece Pin Drive |
| Weight | 26.3 lbs 17% Lighter | 31.7 lbs |
| Diameter | 390mm | 390mm |
| Thickness | 36mm | 36mm |
| Internal Vanes | 72 Directional 20% More | 60 |
| Radial Depth | 62mm | 75mm |
Pad Compatibility
D62 Pad Options
This kit requires Ferodo Racing D62 pads — 62mm radial depth, exclusive to this heavy-duty configuration
| Pad Compound | Essex Part # | Price | Recommended Use |
|---|---|---|---|
| Ferodo DS3.12 D62 | 11.00.00003 | $250 | Maximum aggression — endurance and heavy competition |
| Ferodo DSUNO D62 | — | $250 | High-performance track — strong initial bite with excellent modulation |
| Ferodo DS1.11 D62 | — | $250 | Versatile track compound — wide operating range, consistent feel |
| Ferodo DS2500 D62 | 11.00.00004 | $250 | Dual-purpose street / light track |
Fitment
Compatible Vehicles
Wheel Fitment
Confirmed Clearance
Gallery
Product & Install Images
Spare Parts
Replacement Components
Individual replacement parts available for long-term serviceability
Critical Cautions
D62 pads mandatory on track: Using D54 or D51 pads leaves an unswept ring on the disc face that causes thermal cracking. Only use Ferodo Racing D62 pads with this kit.
Pad retention loop: Remove the pad retention wire loop before track use and use the quick-change spring clip instead for faster pad swaps.
Brake balance: If upgrading front only, use lower friction rear pads to preserve proper brake balance.
Mounting: Do NOT bolt anything between the caliper bracket and suspension upright. Use only original AP Racing bleed screws.
Pro Tips
Brake fluid: Three 500ml bottles recommended for initial install (full system bleed).
New disc prep: Discs have a rust-prevention coating — wash with soap and water before installation.
Mushy pedal fix: If pedal is mushy after install, cycle ABS via scan tool then re-bleed the system.
Disc sides are handed: CP7177-208GC is the right disc and CP7177-209GC is the left disc. They cannot be swapped side-to-side.
Professional Installation
Function Factory Performance offers professional brake service and installation for all AP Racing by Essex brake systems.
Located in Thousand Oaks, California, serving Mustangs, Corvettes, McLarens, and more.
Phone: (805) 206-2523
Lifetime Support
Caliper Reconditioning Program
Built to Last — Backed for Life
Essex is AP Racing’s official North American caliper reconditioning center. When your calipers need servicing after years of hard use, Essex can restore them to factory specification for approximately $155–160 per caliper.
This is not a warranty service — it is a testament to the quality of AP Racing’s manufacturing that calipers can be rebuilt and returned to active competition rather than discarded.
Expert Guidance
Questions About Big Brake Kits?
Our brake specialists can help you choose the right kit and components for your setup. Give us a call or schedule a consultation.
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