BMW M3 E9X / E92 BTCC Big Brake Kit - AP Racing CP9660 Complete Upgrade | XC3 Engineering

XC3 Engineering BTCC Big Brake Kit – BMW E90 / E91 / E92 M3

Transform your BMW E9X M3 into a more capable fast-road and track-focused machine with the XC3 Engineering BTCC Big Brake Kit.

Designed as a complete bolt-on braking solution, this package combines AP Racing CP9660 6-piston Pro 5000 Series R calipers with genuine ex-BTCC 368mm x 36mm brake rotors, custom XC3 Engineering CNC-machined bells and carriers, braided brake lines and all required mounting hardware.

Rather than sourcing individual motorsport components separately, this kit brings everything together into one engineered package for the BMW E90, E91 and E92 M3 platform.

Why Upgrade Your BMW E9X M3 Brakes?

The E9X M3 is a highly capable performance platform, but repeated heavy braking during track use can place substantial thermal stress on the factory system.

As grip, speed and braking intensity increase, brake temperatures rise quickly.

This can lead to:

• Reduced braking consistency
• Increased pedal travel
• Brake fade during sustained use
• Accelerated pad and rotor wear
• Increased brake fluid temperatures

The XC3 BTCC Big Brake Kit is designed to improve front braking capability through larger motorsport rotors, AP Racing multi-piston calipers, race brake pads and braided brake lines.

Key Features

• Complete front big brake conversion
• Designed for applicable BMW E9X M3 models with OEM front hubs
• AP Racing CP9660 6-piston Pro 5000 Series R calipers
• Genuine ex-BTCC 368mm x 36mm brake rotors
• XC3 Engineering custom CNC-machined rotor bells
• XC3 Engineering custom caliper carriers
• AP Racing floating disc bobbin hardware
• Braided brake lines
• Raybestos ST45 ex-BTCC brake pads
• Project Mu H21 pads available as an alternative
• Increased thermal capacity
• Strong, repeatable braking performance
• Suitable for fast-road, track-day and clubsport use

AP Racing CP9660 6-Piston Calipers

At the heart of the system are AP Racing CP9660 Pro 5000 Series R 6-piston calipers.

The CP9660 is a motorsport-focused caliper designed for demanding applications where stiffness, pad stability and repeatable braking response are critical.

Its 6-piston layout distributes clamping force across a large motorsport pad, helping provide strong and predictable braking performance during repeated heavy use.

For track-focused E9X M3 builds, the CP9660 provides a substantial step up from conventional road-car braking hardware.

Genuine Ex-BTCC 368mm x 36mm Rotors

The kit uses genuine ex-BTCC 368mm x 36mm brake rotors.

These rotors are not normally offered by AP Racing as a standard public retail size and are supplied specifically for British Touring Car Championship use.

The rotors supplied with the kit have previously been used during a single BTCC event session before being removed from competition service.

Each rotor is inspected before supply to confirm that it remains in suitable working condition.

Using lightly used BTCC components allows the kit to deliver genuine motorsport braking hardware at a fraction of the cost of an equivalent all-new setup.

XC3 Engineering CNC-Machined Rotor Bells

The BTCC friction rings are paired with custom XC3 Engineering anodised rotor bells.

These are CNC machined specifically to adapt the 368mm motorsport rotors to the BMW E9X M3 front hub arrangement.

The bells provide the correct interface between the hub, AP Racing bobbin hardware and friction ring.

Their anodised finish provides a high-quality appearance and additional surface protection.

XC3 Engineering Caliper Brackets

Custom XC3 Engineering anodised caliper carriers position the AP Racing CP9660 calipers correctly around the 368mm rotors.

The carriers are precision machined for the E9X M3 application and supplied with Chemi Black mounting hardware.

This application-specific design ensures the caliper and rotor are correctly aligned as part of the complete conversion.

Floating Motorsport Rotor Assembly

AP Racing bobbin hardware is supplied to connect the friction rings to the XC3 rotor bells.

The floating arrangement allows the rotor to expand as temperatures increase under heavy braking.

This helps manage the thermal stresses generated through repeated heat cycles and is commonly used in motorsport braking systems.

It also makes future friction ring replacement more straightforward once the rotors reach the end of their usable service life.

Braided Brake Lines

Braided brake lines are included with the kit.

Compared with conventional rubber hoses, braided lines are designed to reduce hose expansion under hydraulic pressure.

This can contribute to a firmer and more consistent pedal feel, particularly when brake temperatures rise during repeated high-load use.

Raybestos ST45 Brake Pads

The standard kit is supplied with ex-BTCC Raybestos ST45 brake pads.

Like the rotors, these are previously used motorsport components selected to help keep the complete package as cost-effective as possible.

Raybestos ST45 is a well-established racing compound suited to repeated heavy braking, track days, clubsport and endurance-style use.

Typical characteristics include:

• Consistent mid-to-high friction
• Predictable brake response
• Strong modulation
• Stable performance through repeated hard braking
• Operating capability up to approximately 700°C rotor temperature
• Relatively rotor-friendly characteristics for a motorsport compound

For mixed fast-road and track use, ST45 offers a strong balance between braking performance, modulation and consumable life.

Optional Project Mu H21 Brake Pads

Project Mu H21 pads are also available as an alternative.

Please contact us if you would prefer the kit supplied with H21 pads.

The H21 is a more aggressive competition-focused compound designed for demanding high-temperature motorsport use.

Typical characteristics include:

• Strong initial bite
• High fade resistance
• Stable high-temperature friction
• Approx. 200°C–850°C operating range
• Motorsport-focused braking performance
• Suitable for repeated high-load use

For dedicated track cars, Time Attack builds or competition vehicles where maximum braking performance is the priority, H21 may be the more suitable choice.

Raybestos ST45 vs Project Mu H21

The best pad choice depends on how the car is used.

Raybestos ST45 is generally better suited to drivers looking for:

• Predictable braking
• Strong modulation
• Consistent track performance
• Manageable consumable wear
• Mixed road and circuit use

Project Mu H21 is more heavily focused on competition.

Its more aggressive response and higher temperature capability make it better suited to:

• Dedicated track cars
• Time Attack builds
• Race cars
• Sustained high-temperature braking
• Drivers prioritising maximum bite and fade resistance

For a road-driven E9X M3 that also sees regular track use, ST45 will generally be the more versatile option.

For dedicated circuit use, H21 may be the better choice.

Used BTCC Rotor & Pad Information

Please be aware that both the rotors and standard Raybestos ST45 pads supplied with this kit are previously used motorsport components.

The rotors have typically been used during a single BTCC event session before being removed from competition use.

They are inspected before supply and only provided when considered to be in usable condition.

The standard pads are also used items.

This approach helps keep the cost of the complete package significantly lower while still providing access to genuine competition-specification braking hardware.

Signs of previous heat cycling, surface marking and cosmetic wear should therefore be expected.

Cost-Effective Replacement Rotors

One of the major long-term advantages of this BTCC-based setup is replacement rotor cost.

Motorsport brake consumables can become expensive, particularly on cars that see frequent circuit use.

The ability to replace worn friction rings with lightly used ex-BTCC 368mm x 36mm rotors can significantly reduce ongoing running costs compared with equivalent new motorsport discs.

This makes the kit particularly attractive for track-focused E9X M3 owners.

Built for the BMW E9X M3 Platform

The E9X M3 combines high engine performance, strong chassis capability and relatively high vehicle weight.

Under repeated heavy braking, this creates substantial thermal demand at the front axle.

The XC3 BTCC Big Brake Kit is designed to give the platform a more capable braking system for:

• Fast-road use
• Track days
• Clubsport
• Time Attack
• High-grip tyre setups
• Higher-performance builds

For cars running semi-slick tyres or seeing regular circuit use, increased braking thermal capacity can make a significant difference to consistency over repeated laps.

BMW E90 M3

The E90 M3 saloon shares the same performance-focused platform and can benefit significantly from increased front braking capability during demanding use.

For track and fast-road builds, the CP9660 and 368mm rotor combination provides a strong foundation for repeatable braking performance.

BMW E91 M3

For applicable E91-based conversions or models using the supported OEM front hub arrangement, the same brake system architecture can be used where fitment is confirmed.

Exact compatibility should always be checked before ordering.

BMW E92 M3

The E92 M3 Coupe is one of the most popular E9X platforms for track and fast-road builds.

With higher-grip tyres, suspension upgrades and frequent circuit use, front brake temperatures can rise rapidly.

The XC3 BTCC kit provides a motorsport-derived solution designed to improve thermal capacity and braking consistency.

Ideal for Track-Day & High-Performance Builds

The XC3 BTCC Big Brake Kit is particularly well suited to:

• BMW E90 M3 track builds
• BMW E92 M3 track builds
• Applicable E91 M3 setups
• Higher-grip tyre configurations
• Cars running semi-slick tyres
• Fast-road builds
• Clubsport cars
• Time Attack vehicles
• Dedicated track cars

Wheel Clearance

Due to the use of 368mm rotors and large AP Racing CP9660 calipers, wheel clearance must be checked before ordering.

Compatibility depends on:

• Wheel diameter
• Wheel width
• Wheel offset
• Spoke profile
• Internal barrel clearance

Wheel diameter alone does not guarantee caliper clearance.

If you are unsure whether your wheels will clear the kit, please contact us before ordering.

Brake Fluid

For track use, the braking system should be paired with a suitable high-temperature performance brake fluid.

Brake fluid should also be replaced regularly on vehicles that see frequent circuit use.

Even a high-performance brake kit can suffer from poor pedal consistency if the fluid exceeds its working temperature range.

Professional Installation

Professional installation is strongly recommended.

Installation should include:

• Caliper carrier installation
• Rotor bell and friction ring assembly
• Brake line installation
• Correct hardware torque procedures
• Brake system bleeding
• Wheel clearance checks
• Pad and rotor inspection

The braking system is safety critical and should only be installed by a competent technician.

Made to Order

XC3 Engineering BTCC Big Brake Kits are made to order.

We aim to keep the individual components available wherever possible, but certain parts may occasionally be subject to a lead time.

Please contact us before ordering if you require confirmation of current availability or have a specific deadline.

Fitment

Designed for applicable BMW E9X M3 models using OEM front hubs, including:

• BMW E90 M3
• BMW E91 M3 where applicable
• BMW E92 M3

Model year range: 2006–2012.

Exact fitment should be confirmed against the vehicle specification before ordering.

If you're unsure whether this kit is suitable for your BMW, contact us and we'll be happy to help confirm compatibility.

Kit Contents

The XC3 Engineering BTCC Big Brake Kit includes:

• 2x AP Racing CP9660 Pro 5000 Series R 6-piston calipers
• 2x ex-BTCC 368mm x 36mm brake rotors
• XC3 Engineering custom anodised rotor bells
• XC3 Engineering custom anodised caliper brackets
• Chemi Black bracket hardware
• Braided brake lines
• 2x AP Racing bobbin kits
• Ex-BTCC Raybestos ST45 brake pads

Project Mu H21 brake pads are also available as an alternative. Please contact us for this option.

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