MMX 325mm Rear 2-Piece Rotor Conversion | MINI F56

MMX 325mm Rear 2-Piece Rotor Conversion – MINI F56 JCW

Upgrade the rear braking performance, thermal capacity and durability of your MINI F56 John Cooper Works with the MMX 325mm Rear 2-Piece Rotor Conversion.

Unlike a simple replacement rear disc, this MMX kit increases the rotor size to 325mm x 10mm and includes dedicated caliper carrier brackets to correctly reposition the factory rear calipers around the larger disc.

The result is a more substantial rear braking package with improved heat management, reduced risk of warping and cracking, more consistent braking under repeated hard use and a much more purposeful two-piece appearance.

Designed for fast-road and track-focused MINI builds, the MMX rear conversion works particularly well alongside the matching 335mm front two-piece rotor kit.

Why Upgrade the Rear Brake Rotors?

The factory rear braking system is designed primarily around road use and standard power levels.

During repeated hard braking, rear disc temperatures can rise significantly.

Excessive heat can contribute to:

• Brake fade
• Reduced braking consistency
• Disc distortion
• Surface cracking
• Accelerated pad wear
• Reduced confidence during repeated stops

The MMX 325mm rear conversion is designed to manage heat more effectively while retaining the original rear calipers.

Key Features

• MMX 325mm rear two-piece rotor conversion
• Designed for MINI F-Series JCW applications
• 325mm diameter
• 10mm thickness
• Larger than the factory rear rotor
• Includes dedicated rear caliper carrier brackets
• Retains factory rear calipers
• Compatible with OEM brake pads
• Compatible with aftermarket performance pads
• Fully floating two-piece construction
• Specific left- and right-hand rotors
• 6061-T6 aerospace-grade aluminium centre hats
• Proprietary high-temperature friction rings
• MMX directional grooved friction surface
• Floating bobbin mounting system
• Up to 30% cooler running than OE
• Up to 30% improved cooling efficiency
• Improved thermal capacity
• Reduced risk of warping
• Reduced risk of cracking
• Suitable for fast-road and track use
• Matching 335mm front rotors available
• Complete installation hardware included
• MMX SKU MMR31-1411R

325mm x 10mm Rear Rotor Conversion

The MMX system increases the rear brake rotor diameter to 325mm while retaining a 10mm disc thickness.

Because the rotor is larger than the original rear disc, the factory caliper must be repositioned further outward.

MMX achieves this using a dedicated carrier bracket rather than a simple spacer.

Dedicated Caliper Carrier Brackets

The kit includes purpose-designed rear caliper carrier brackets matched in the JCW red finish.

These reposition the factory rear calipers so they sit correctly over the larger 325mm rotors.

MMX specifically uses a dedicated bracket rather than a basic spacer to provide improved:

• Alignment
• Strength
• Rigidity
• Fitment accuracy
• Long-term reliability

This makes the conversion a proper engineered solution rather than a simple spacing arrangement.

Retains the Factory Rear Calipers

One of the key advantages of this conversion is that the standard MINI rear calipers remain in place.

This means you can significantly upgrade the rear disc setup without replacing the entire braking system.

It retains:

• OEM calipers
• OEM-style pad shape
• Factory hydraulic system
• Straightforward servicing

Two-Piece Floating Construction

The MMX rotor separates the friction ring from the centre hat.

This allows the two components to expand independently as brake temperatures rise.

During repeated hard braking, the friction ring can expand both radially and axially without transferring the same level of thermal stress through the assembly.

Potential benefits include:

• Reduced rotor distortion
• Reduced cracking
• More consistent pad contact
• Improved high-temperature durability
• Longer disc life

Up to 30% Cooler Than OE

MMX states that the 325mm rear discs can run up to 30% cooler than the original rear discs.

They also quote up to 30% improved cooling efficiency.

Lower rotor temperatures can help provide:

• More consistent braking
• Reduced heat soak
• Improved pad life
• Reduced thermal stress
• Better repeatability during hard driving

Improved Thermal Capacity

The larger 325mm rotor provides a greater thermal mass and surface area than the factory rear disc.

This allows the braking system to absorb and dissipate more heat before reaching critical temperatures.

This becomes especially valuable during:

• Track sessions
• Repeated high-speed braking
• Mountain-road driving
• Fast-road use
• Higher-power builds

Floating Bobbin System

The iron friction ring is connected to the aluminium centre hat using a floating bobbin mounting system.

This allows controlled movement as temperatures change.

The design helps reduce the stresses that can develop in a rigid one-piece brake disc.

6061-T6 Aluminium Centre Hats

The MMX rear rotors use 6061-T6 aerospace-grade aluminium centre hats.

Using aluminium rather than a full one-piece iron rotor helps reduce unnecessary mass.

This can help reduce:

• Unsprung weight
• Rotational mass

while maintaining the strength required for performance braking.

Directional Grooved Friction Surface

The rotor face uses MMX's directional groove pattern.

The grooves help:

• Increase initial bite
• Clean the pad surface
• Remove brake debris
• Maintain a consistent pad-to-disc interface

This provides a useful balance between brake feel, performance and longevity.

Specific Left & Right Rotors

The kit uses dedicated left- and right-hand brake rotors.

This ensures the rotor design and groove pattern operate in the intended direction on both sides of the vehicle.

Correct installation orientation is important for optimum performance.

Improved Brake Consistency

One of the biggest advantages of an upgraded rotor becomes apparent during repeated braking.

Rather than focusing solely on one maximum-effort stop, the MMX system is designed to perform more consistently as temperatures rise.

This is particularly valuable during:

• Track driving
• Repeated fast-road braking
• Performance road use
• Extended downhill sections

Reduced Risk of Warping

As conventional one-piece rotors heat up, thermal expansion can create stress within the disc.

The floating MMX design allows the friction ring to expand more naturally.

This helps reduce the thermal loading that contributes to disc distortion and vibration.

Reduced Risk of Cracking

Repeated extreme heat cycles can also lead to cracking in conventional rotors.

The two-piece floating design helps manage these temperature changes more effectively, reducing stress within the friction ring.

Compatible with OEM Pads

The MMX conversion remains compatible with OEM-shape rear brake pads.

For road-focused cars, this means you can retain a quieter and more refined pad compound while benefiting from the improved rotor system.

Compatible with Performance Pads

The conversion also works with suitable aftermarket performance pads.

This allows the braking setup to be tailored around the intended use.

Fast-Road Pads

Ideal for:

• Strong cold performance
• Increased temperature range
• Reasonable noise levels
• Everyday road use

Track Pads

Better suited to:

• Repeated high-temperature braking
• Track sessions
• Maximum fade resistance
• High-friction performance

Ideal for Fast-Road Builds

For a fast-road MINI JCW, the MMX rear conversion complements upgrades such as:

• Performance brake pads
• Braided brake lines
• High-temperature brake fluid
• Performance tyres
• Lowering springs
• Coilovers
• Increased engine output

Ideal for Track Use

Track driving places far greater thermal demands on the braking system than normal road use.

The larger two-piece rear rotors provide improved:

• Heat capacity
• Cooling
• Durability
• Repeatability

This makes them particularly well suited to track-focused MINI builds.

Matching 335mm Front Rotors

MMX also offers its 335mm x 30mm two-piece front rotor upgrade for the F-Series MINI JCW.

Combining the front and rear systems creates a complete MMX two-piece braking package.

Front:

• 335mm x 30mm
• Two-piece floating design
• Factory JCW front caliper fitment

Rear:

• 325mm x 10mm
• Two-piece floating design
• Dedicated caliper carrier brackets
• Factory rear caliper fitment

Important Electric Handbrake Exclusion

The MMX 325mm rear rotor conversion does not fit MINI F-Series models equipped with an electric parking brake.

This must be checked before ordering.

MINI F56 John Cooper Works

The MMX rear rotor conversion is particularly aimed at MINI F56 JCW applications.

It is ideal for:

• Standard JCW models
• Tuned JCW models
• Fast-road builds
• Track-focused builds

Wider F-Series MINI Fitment

MMX also lists compatible applications across the F-Series MINI range, including:

• MINI F55
• MINI F56
• MINI F57

Its wider fitment table also references F54 and F60 applications, but the product is specifically designed around the F-Series JCW rear brake arrangement.

Exact brake and parking-brake specification should always be confirmed before ordering.

Compatibility

Primary application:

• MINI F56 John Cooper Works

Also suitable for compatible F-Series MINI JCW applications using the appropriate rear brake setup.

Not suitable for:

• Electric handbrake variants

Brake requirements:

• Factory rear calipers retained
• Dedicated MMX carrier brackets included

Please confirm exact vehicle and rear brake specification before ordering.

What's Included?

The MMX 325mm Rear 2-Piece Rotor Conversion includes:

• 1x left-hand 325mm x 10mm two-piece rear rotor
• 1x right-hand 325mm x 10mm two-piece rear rotor
• 6061-T6 aluminium centre hats
• Floating bobbin assemblies
• Dedicated rear caliper carrier brackets
• JCW red carrier finish
• Required installation hardware

Supplied as a complete rear axle conversion kit.

Brake pads are not included.

Explore More MINI F56 Brake Upgrades

Looking to improve your MINI braking system further? Explore our range of performance components.

MINI F56 Parts – Browse braking, suspension and performance upgrades for MINI F56 models.

MMX Performance – Explore MMX braking, chassis, cooling and performance upgrades.

Brake Discs – Browse uprated one-piece and two-piece brake rotor options.

Brakes – Explore brake pads, discs, braided lines, brake fluid and supporting upgrades.

 **Please note: the rear 2-piece discs/rotors for the MINI F-Series does not fit the electric handbrake variants.