AP Racing by Essex 2001-2006 BMW E46 3-Series 330i 325i Competition Brake Kit (Rear CP8350/325mm)
or as low as $270.75/mo with Affirm
AP Racing by Essex
Competition Rear Brake Kit CP8350/325mm — BMW E46
A purpose-built rear competition brake kit for the 2001–2006 BMW E46 3-Series. The CP8350 4-piston fixed caliper and 325x32mm floating disc deliver massive stopping power and heat capacity, replacing both the OE rear brakes and parking brake assembly.
Rear Axle Competition
Dedicated Rear Brake Kit for the BMW E46 3-Series
This is a rear-axle-only competition brake kit designed for the 2001–2006 BMW E46 platform. It replaces the factory single-piston sliding caliper and 320x22mm vented disc with a far more capable 4-piston fixed caliper and 325x32mm two-piece floating J Hook disc.
The CP8350 caliper weighs just 4.8 lbs — significantly lighter than the OE unit at 7.53 lbs — while delivering dramatically improved clamping force through four equally-sized 28.575mm pistons. The larger, thicker disc provides greater thermal mass for sustained heavy braking, with 70 directional vanes versus the factory 35.
Hard anodized finish on both calipers and disc hats ensures long-term durability under extreme track conditions without the chipping or flaking associated with paint and powder coat finishes.
Key Advantages
Engineered Without Compromise
Eight reasons this rear kit transforms E46 braking performance
4-Piston Fixed Caliper
Replaces the OE single-piston sliding caliper with a rigid 4-piston fixed design. Equal piston sizing delivers uniform pad wear and consistent clamping force across the entire pad face.
Hard Anodized Finish
Hard anodizing grows an aluminum oxide layer directly from the caliper body via electrical current in an acid bath. Far more durable than paint or powder coat under sustained track temperatures. Will not chip, flake, or degrade.
325x32mm Floating Disc
Larger and thicker than the OE 320x22mm rear disc, with 70 directional internal vanes versus factory 35. Dramatically improved heat dissipation and thermal capacity for sustained high-load braking.
~5 lbs Lighter
Saves approximately 5 lbs of unsprung weight from the rear axle. The CP8350 caliper alone saves 2.73 lbs per side over the OE unit, with further savings from the optimized disc assembly.
70-Vane J Hook Discs
Double the internal vane count of the OE rear disc. Directional vane geometry with J Hook slot pattern creates superior airflow, uniform heat distribution, and consistent bite from first lap to last.
Two-Piece Floating Design
10-bolt floating bobbin drive with 6061 heat-treated billet aluminum hats. Accommodates thermal expansion without coning or warping that plagues one-piece OE discs under heavy use.
Spiegler Brake Lines
DOT-compliant stainless steel brake lines with abrasion-resistant coating and lifetime warranty included in every kit. Firmer pedal feel and improved response versus rubber OE lines.
Broad Pad Selection
Compatible with pads from Ferodo, Carbotech, Hawk, Pagid, PFC, Endless, Project Mu, and more. Five D50 compounds available from Essex at $125 each, plus dozens of aftermarket options.
Complete Kit
What’s In The Box
- AP Racing CP8350 Competition Calipers (Pair)4-piston fixed, 4.8 lbs each — hard anodized finish with stainless steel pistons and anti-knockback springs
- AP Racing 325x32mm J Hook Racing Discs (Pair)70 directional vanes — 2-piece floating with 6061 hard-anodized billet aluminum hats and 10-bolt attachment hardware
- Caliper Mounting Brackets & HardwarePrecision-machined brackets with aircraft-quality mounting hardware for the E46 rear knuckle
- Spiegler Stainless Steel Brake Lines (Pair)DOT-approved with abrasion-resistant coating and lifetime warranty
- Detailed Installation InstructionsStep-by-step guide including parking brake removal procedure and torque specifications
- Not Included: Brake PadsD50 pads sold separately — DS2500, DS3000, DS1.11, DSUNO, or DS3.12 ($125 each)
- Not Included: Pad Tension ClipsOptional CP8350 tension clip add-on ($39.90)
Technical Data
Specifications
Caliper (CP8350)
4-Piston Fixed CompetitionDisc (325x32mm)
70-Vane J Hook Racing DiscEngineering
Technology Deep-Dive
4-Piston Fixed Design
The CP8350 uses four equally-sized 28.575mm pistons in a rigid fixed body, replacing the OE single-piston sliding caliper. Fixed calipers apply force equally from both sides of the disc, delivering perfectly uniform pad wear and eliminating the flex inherent in sliding caliper designs.
Equal piston sizing simplifies thermal management and ensures balanced pad contact across the entire friction surface.
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.
Two-Piece Floating Assembly
One-piece discs cone when heated unevenly — the center heats faster than the outer edge, causing the disc to warp. The two-piece floating design uses oblong bobbin mounting holes that allow radial expansion without distortion.
The 10-bolt floating system accommodates thermal growth, virtually eliminating stress cracks, pad taper wear, and the vibration that comes from distorted one-piece discs. 6061 heat-treated billet aluminum hats reduce unsprung weight while maintaining structural integrity.
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. The 70 directional internal vanes — double the OE 35 — dramatically improve airflow and cooling capacity.
Superior Heat Capacity
The 325x32mm disc is 10mm thicker than the OE 320x22mm rear disc, providing substantially greater thermal mass. Combined with 70 directional vanes (vs. OE 35), the disc can absorb and dissipate far more heat before reaching critical temperatures.
Greater heat capacity means later fade onset, more consistent stopping power through long sessions, and significantly longer disc life.
Lightweight Competition Design
Every component is optimized for minimum weight. The CP8350 caliper weighs just 4.8 lbs versus the OE 7.53 lbs — a 36% reduction. The disc assembly at 15.93 lbs is lighter than the OE 16.5 lbs despite being thicker and having twice the vane count.
Approximately 5 lbs of total unsprung weight savings from the rear axle improves suspension response, grip, and reduces fatigue on rear suspension components.
How It Compares
Essex/AP Racing vs. OE E46 Rear
| Specification | Essex CP8350 | OE E46 Rear |
|---|---|---|
| Weight (no pads) | 4.8 lbs 36% Lighter | 7.53 lbs |
| Configuration | 4-Piston Fixed 4x More Pistons | 1-Piston Sliding |
| Design | Fixed Forged Aluminum | Sliding Cast Iron |
| Finish | Hard Anodized Track Grade | Paint |
| Specification | Essex/AP Disc | OE E46 Rear |
|---|---|---|
| Type | 2-Piece Floating Superior | 1-Piece Solid |
| Weight | 15.93 lbs 3% Lighter | 16.5 lbs |
| Diameter | 325mm | 320mm |
| Thickness | 32mm 45% Thicker | 22mm |
| Internal Vanes | 70 Directional 2x More | 35 |
| Slot Pattern | J Hook Optimized | None (Plain) |
Pad Compatibility
D50 Pad Options
Five compounds available from Essex, plus broad aftermarket cross-reference compatibility
| Pad Compound | Price | Recommended Use |
|---|---|---|
| Ferodo DS2500 | +$125 | Dual-purpose street / light track — strong initial bite, low noise |
| Ferodo DS3000 | +$125 | Club track day compound — excellent modulation and release |
| Ferodo DS1.11 | +$125 | Versatile track compound — wide operating range, consistent feel |
| Ferodo DSUNO | +$125 | High-performance track — strong initial bite with excellent modulation |
| Ferodo DS3.12 | +$125 | Maximum aggression — endurance and heavy competition |
Fitment
Compatible Vehicles
Wheel Fitment
Clearance Information
Gallery
Product & Install Images
Spare Parts
Replacement Components
Individual replacement parts available for long-term serviceability
Critical Warnings
PARKING BRAKE ELIMINATED: This kit completely eliminates the OE parking brake. The OE parking brake drum must be removed during installation. If parking brake functionality is required, install a line lock or hydraulic handbrake as an alternative.
RWD only: This kit is confirmed for RWD E46 models only. AWD xi fitment has not been verified by Essex.
Brake balance: If upgrading rear only, use a higher friction front pad to preserve proper front-rear brake balance. Conversely, if pairing with an upgraded front kit, match compound aggressiveness appropriately.
Mounting: Do NOT bolt anything between the caliper bracket and rear knuckle. 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: CP3870-138GC is the right disc and CP3870-139GC is the left disc. They cannot be swapped side-to-side.
Burnishing available: Pre-burnishing ($100) ensures optimal disc surface prep — recommended for competition use.
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 BMWs, 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 $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 This Rear Brake Kit?
Our brake specialists can help you choose the right pad compounds, verify wheel clearance, and plan your rear brake upgrade. Give us a call or schedule a consultation.
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