VW Golf GTI / R MK5 MK6 – BTCC Big Brake Kit – AP Racing CP9660 Complete Upgrade | XC3 Engineering

XC3 Engineering BTCC Big Brake Kit – VW Golf GTI / R MK5 & MK6

Upgrade the braking performance of your Volkswagen Golf GTI or Golf R MK5/MK6 with the XC3 Engineering BTCC Big Brake Kit, featuring AP Racing CP9660 6-piston Pro 5000 Series R calipers.

Built around genuine ex-BTCC 368mm x 36mm brake rotors, custom XC3 Engineering CNC-machined bells and carriers, braided brake lines and competition brake pads, this complete front brake conversion is designed for demanding fast-road, track-day and motorsport use.

For modified Golf GTI and Golf R builds running increased power, higher-grip tyres or regular circuit use, the XC3 BTCC kit provides a substantial upgrade in braking capability, thermal capacity and consistency under repeated heavy braking.

Why Upgrade Your Golf MK5 / MK6 Brakes?

The Golf GTI and Golf R platforms respond extremely well to power, tyre and chassis upgrades, but as performance increases the factory braking system can become one of the limiting factors.

Repeated heavy braking generates substantial heat, which can reduce pedal consistency and braking performance when the original system is pushed beyond its intended operating range.

The XC3 BTCC Big Brake Kit upgrades the front braking system with:

• AP Racing CP9660 6-piston calipers
• 368mm x 36mm ex-BTCC motorsport rotors
• High-performance race brake pads
• Braided brake lines
• Floating AP Racing rotor hardware
• Custom XC3 Engineering bells and carriers

The result is a significantly more capable braking package for fast-road, track-day and competition-focused Golf builds.

AP Racing CP9660 6-Piston Calipers

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

The CP9660 is a motorsport-focused caliper designed for demanding applications where stiffness, consistent pad pressure and reliable braking performance are critical.

Its 6-piston design distributes clamping force across a large motorsport brake pad, helping provide strong braking performance and consistent pedal response during repeated heavy use.

For track-focused Golf builds, the CP9660 represents a substantial upgrade over conventional road-car braking hardware.

Genuine Ex-BTCC 368mm x 36mm Rotors

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

These rotor dimensions are not normally offered for general public sale through AP Racing and are supplied specifically for British Touring Car Championship applications.

The rotors included with this kit have previously been used during a single session at a BTCC event 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 XC3 Engineering to offer genuine competition-level braking hardware at a considerably more accessible price than an equivalent all-new motorsport system.

XC3 Engineering CNC-Machined Rotor Bells

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

These components are CNC machined specifically to integrate the large motorsport rotors with the Volkswagen Golf MK5 and MK6 hub configuration.

The bells are anodised for a high-quality finish and additional surface protection.

Together with the AP Racing bobbin hardware, they form the floating rotor assembly used by the kit.

XC3 Engineering Caliper Carriers

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

The carriers are precision machined and anodised, with Chemi Black mounting hardware supplied as part of the package.

Application-specific carriers are essential when adapting motorsport braking hardware to a production vehicle, ensuring the caliper is correctly positioned relative to the rotor.

Floating Motorsport Rotor Assembly

The kit includes AP Racing bobbin hardware to connect the BTCC friction rings to the XC3 Engineering rotor bells.

A floating disc arrangement allows the friction ring to expand as temperatures increase during heavy braking.

This helps manage the thermal stresses generated during repeated high-load use and is commonly used in motorsport braking systems where rotor temperatures can become extremely high.

Braided Brake Lines

Braided brake lines are included with the conversion.

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

This can help provide a firmer and more consistent pedal feel, particularly during repeated heavy braking when brake system temperatures increase.

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 overall package as cost-effective as possible.

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

Typical characteristics include:

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

For track-day and clubsport builds where consistency and manageable wear are important, ST45 is an excellent all-round option.

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 performance
• Approx. 200°C–850°C operating range
• Motorsport-focused friction characteristics
• Suitable for repeated high-load braking

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

Raybestos ST45 vs Project Mu H21

Choosing the correct brake pad depends heavily on how the vehicle will be used.

Raybestos ST45 is generally better suited to drivers looking for a balance between braking performance, modulation, rotor wear and track-day usability.

It provides strong, predictable braking without being as aggressive as a more specialised high-temperature race compound.

Project Mu H21 is more heavily focused on motorsport.

Its higher operating temperature capability and more aggressive friction characteristics make it better suited to dedicated circuit cars and competition builds where maximum braking performance is the priority.

For mixed fast-road and track use, ST45 will generally be the more versatile option.

For dedicated circuit use, H21 may be better suited to sustained high-temperature braking.

Used BTCC Rotor & Pad Information

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

The BTCC rotors have typically been used during a single session at a British Touring Car Championship event before being removed from competition use.

The rotors are inspected prior to supply to confirm that they remain in suitable working condition.

The brake pads are also previously used items.

Using these lightly used motorsport components helps keep the overall cost of the kit significantly lower while still providing access to genuine competition-specification braking hardware.

Cosmetic markings, heat cycling and signs of previous use should therefore be expected.

Ideal for Track-Day & High-Performance Golf Builds

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

• VW Golf GTI MK5 track builds
• VW Golf GTI MK6 track builds
• VW Golf R MK6 performance builds
• Higher-powered Golf models
• Cars running semi-slick or high-grip tyres
• Track-day vehicles
• Clubsport builds
• Time Attack cars
• Performance road cars that see regular circuit use

As engine performance and tyre grip increase, upgrading braking capability becomes increasingly important for maintaining repeatable performance.

Wheel Clearance

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

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 current wheels will clear the brake kit, please contact us before ordering.

Brake Fluid

For track use, the braking system should be paired with a suitable high-performance brake fluid capable of handling elevated temperatures.

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

Even a high-performance brake system can suffer from poor pedal consistency if the fluid reaches its boiling point.

Professional Installation

Professional installation is strongly recommended.

Correct installation should include:

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

Suitable for applicable:

• Volkswagen Golf GTI MK5
• Volkswagen Golf GTI MK6
• Volkswagen Golf R MK6

Please confirm your exact vehicle specification before ordering.

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

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 caliper 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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