AP Racing by Essex 2024-2026 Ford Mustang S650 GT Dark Horse Radi-CAL ENP Competition Brake Kit (Rear CP9451/365mm)
- Track-Ready: Complete rear ENP brake kit engineered for extended track sessions on 2024+ S650 Dark Horse & GT Performance Pack
- 15 lbs Lighter: Saves ~15 unsprung lbs on rear axle versus OEM Dark Horse and GT PP brakes
- ENP Finish: Jewel-like Electroless Nickel Plated caliper – incredibly durable and easy to clean
- Radi-CAL Technology: AP Racing’s patented asymmetric design with 30%+ stiffness increase
- 4-Piston CP9451: Ventilated domed-back stainless steel pistons with anti-knockback springs
- 72-Vane Discs: 365x30mm fully floating J Hook racing discs with hard-anodized aluminum hats
- Parking Brake Retained: Full OE electronic parking brake functionality with included caliper spacers
- OEM Integration: Clears OE 19” Dark Horse wheels without spacer, works with stock ABS/master cylinder
- Spiegler Lines: DOT-approved stainless steel brake lines with abrasion-resistant coating included
- Pad Options: Compatible with Ferodo, Hawk, CL Brakes, Pagid, PFC, Carbotech, Cobalt, and more
or as low as $445.75/mo with Affirm
AP Racing by Essex
Radi-CAL ENP Competition Brake Kit 2024+ Ford Mustang S650 Dark Horse · GT Performance Pack
Complete rear brake kit engineered for extended track sessions. Saves ~15 unsprung lbs versus OEM while retaining full electronic parking brake functionality.
Rear Axle Upgrade
Complete the Package With a Purpose-Built Rear Kit
The OEM Dark Horse and GT Performance Pack rear brakes were designed for street driving compromises. On track, they overheat, fade, and hold back the potential of your front brake upgrade.
The AP Racing by Essex CP9451 rear kit saves approximately 15 lbs of unsprung weight versus OEM while delivering consistent, fade-free stopping power through extended track sessions. Every component is rated for sustained high-temperature operation.
Designed to pair with the AP Racing by Essex CP9668/390mm front kit for a balanced, championship-proven brake system front to rear.
Why Choose This Kit
Engineered Without Compromise
Every component designed for one purpose: dominating extended track sessions
15 lbs Lighter
Saves approximately 15 unsprung lbs on the rear axle versus OEM Dark Horse and GT PP brakes
ENP Finish
Jewel-like electroless nickel plating won’t chip, flake, or fade at track temps. Incredibly durable and easy to clean.
Radi-CAL Tech
AP Racing’s patented asymmetric design delivers 30%+ more stiffness than conventional calipers for superior pedal feel.
OEM Integration
Clears OE 19″ Dark Horse wheels without spacers. Full electronic parking brake (EPB) retained. Seamless ABS integration.
Parking Brake
Retains full OE electronic parking brake functionality. Caliper spacers for EPB included in every kit.
Pad Options
Commonly available pad shapes from Ferodo, Hawk, CL Brakes, Pagid, PFC, Carbotech, and more.
Quick Pad Change
Bridge bolts pop out with a 6mm hex. Change pads trackside faster than you can remove the wheel.
Lifetime Support
Essex is AP Racing’s official rebuild center. Professional reconditioning available for the life of your kit.
Complete Kit
What’s In The Box
-
AP Racing Radi-CAL Pro5000R Calipers (Pair)CP9451 4-piston (4.85 lbs each) — ENP finish with ventilated domed-back stainless steel pistons and anti-knockback springs
-
AP Racing J Hook Racing Discs (Pair)365x30mm with 72 directional vanes — 2-piece fully floating design with 6061 hard-anodized aluminum hats
-
Caliper Spacers for Electronic Parking BrakePrecision-machined spacers to retain full OE EPB functionality
-
Spiegler Stainless Steel Brake Lines (Pair)DOT-approved with abrasion-resistant coating for improved pedal feel and durability
-
Mounting HardwareAircraft-quality hardware for secure caliper and disc installation
-
Detailed Installation InstructionsStep-by-step guide for proper fitment
Technical Data
Specifications
Caliper (CP9451)
4-Piston Radi-CAL Pro5000R
Disc (365x30mm)
72-Vane J Hook Racing Disc
How It Compares
Essex/AP Racing vs. OEM
| Specification | Essex/AP Racing BBK | S650 OEM Rear |
|---|---|---|
| Caliper Weight | 4.85 lbs 46% Lighter | 9.0 lbs |
| Caliper Type | Radi-CAL Pro5000R 4-Piston | Single-Piston Sliding |
| Disc Weight | 15.4 lbs 28% Lighter | 21.3 lbs |
| Disc Diameter | 365mm Larger | 355mm |
| Disc Thickness | 30mm | 28mm |
| Internal Vanes | 72 Directional 36% More | 53 |
| Disc Type | 2-Piece Floating J Hook | 1-Piece Iron |
| Weight Savings | ~15 lbs saved on rear axle | |
Pad Compatibility
Choose Your Compound
Pad shape: 132.4 x 42 x 16.7mm — commonly available from every major manufacturer
| Manufacturer | Part Number | Available Compounds |
|---|---|---|
| Ferodo | FRP3018 | DS2500, DS1.11, DS3.12 |
| Hawk | HB718.654 | HPS, DTC-60, DTC-70 |
| CL Brakes | 5004W42T17 | RC5+, RC6E, RC6, RC8 |
| Pagid | 2126 | RSL1, RSL29, RSC1 |
| PFC | 7768.XX.16 | 01, 08, 11 |
| Carbotech | CTCP9449 | XP8, XP10, XP12, AX6 |
| Cobalt | AP13 | XR1, XR2, XR3, XR4 |
| Alcon | PNF0084X276.4 | Various |
| AP Racing | CP3215D42 | Various |
| Mintex | 1970 16.75 | Various |
Fitment
Compatible Vehicles
Wheel Fitment
Confirmed Wheels & Downloads
See It In Action
Videos
Gallery
Product & Install Images
Not Included
Brake Pads: Racing pads are a personal choice. Select your preferred compound at checkout — Ferodo DS2500, DS1.11, DSUNO, or DS3.12 available as add-on.
Pad Tension Kit: Billet aluminum blocks with stainless steel springs eliminate brake noise. Available as add-on.
Important Notes
Application: Designed for track/competition use. Off-road use only.
Front Kit Pairing: This rear kit is designed to pair with the AP Racing by Essex CP9668/390mm front kit for optimal brake balance.
Professional Installation
Function Factory Performance offers professional installation and track support for your AP Racing brake system.
Located in Thousand Oaks, CA — serving enthusiasts across Southern California with expert brake system installation and setup.
Spare Parts & Accessories
Replacement Components
Ready to Upgrade?
Professional Installation Available
Function Factory Performance offers expert installation and track support for your AP Racing brake system. Located in Thousand Oaks, California.
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