MMX Crank hub & capture plate | S55 | N55
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MMX Crank Hub & Capture Plate – BMW N55 & S55
Protect your BMW N55 or S55 engine against one of its most widely discussed timing-related weak points with the MMX Single-Piece Crank Hub and optional Capture Plate.
Designed for N55- and S55-powered BMW applications including the M135i, M235i, 335i, 435i, F87 M2, F87 M2 Competition, F80 M3 and F82/F83 M4, the MMX crank hub replaces the factory multi-piece arrangement with a single-piece billet steel component.
The one-piece construction is designed to prevent the friction interfaces within the original crank hub assembly from slipping, helping maintain correct engine timing under increased power, torque and hard use.
For additional security, the MMX Capture Plate can be fitted over the crank bolt to physically prevent it from rotating or loosening.
Why Upgrade the N55 / S55 Crank Hub?
The original N55 and S55 crank hub uses a multi-piece design that relies on friction between the individual components.
If the hub slips relative to the crankshaft, engine timing can move out of its intended position.
In severe cases, this can lead to incorrect valve timing and potentially significant engine damage.
The MMX single-piece crank hub is designed to eliminate the friction interface between the hub components by replacing them with a one-piece billet assembly.
Key Features
- MMX single-piece crank hub
- Designed for BMW N55 and S55 engines
- Replaces the factory multi-piece crank hub design
- Helps prevent crank hub slip
- Single-piece billet construction
- Machined from EN36 steel
- Heat-treated for strength and durability
- 0.75mm case hardening
- New crank bolt supplied
- Suitable for standard and tuned engines
- Optional MMX Capture Plate available
- Capture Plate helps prevent crank bolt loosening
- Unpinned design provides simpler installation than pinned alternatives
- Higher-power 4-pin MMX crank hub also available
- MMX crank hub part number MMR20-1001
- MMX Capture Plate part number MMR20-1002
Single-Piece Crank Hub Design
The key difference between the MMX crank hub and the factory assembly is the one-piece construction.
Instead of relying on multiple friction-driven components, the MMX hub is manufactured as a single component.
This means the individual friction plates within the original design can no longer rotate independently of one another.
The result is a substantially more secure mechanical connection within the timing drive.
Helps Prevent Timing Slip
Crank hub slip can allow the relationship between the crankshaft and camshaft timing to change.
Even a relatively small movement can cause the engine timing to move outside its intended operating range.
In severe cases, incorrect timing can create the risk of piston-to-valve contact.
The MMX one-piece design is intended to significantly reduce this risk by eliminating the slipping interface found within the original hub assembly.
EN36 Billet Steel Construction
The MMX crank hub is machined from billet EN36 steel.
The component is then heat-treated and given approximately 0.75mm of case hardening.
This provides:
- High surface hardness
- Strong core material
- Excellent wear resistance
- High mechanical strength
- Long-term durability
The material and manufacturing process are designed to cope with the considerable loads transmitted through the timing system.
New Crank Bolt Included
MMX supplies a new crank bolt with the crank hub.
Correct installation and torque procedure are critical when replacing the crank hub.
MMX specifies an installation torque of:
- 100Nm initial torque
- Followed by 270 degrees additional rotation
This work should be carried out by an experienced BMW specialist using the correct locking and timing equipment.
Optional MMX Capture Plate
For additional security, the MMX crank hub can be combined with the MMX Capture Plate.
The capture plate fits over the head of the crank bolt and physically prevents the bolt from rotating loose.
This provides a second layer of protection alongside the single-piece crank hub itself.
How the Capture Plate Works
The capture plate completely surrounds the head of the crank bolt.
Once secured in position, the bolt is physically prevented from rotating.
This helps address the possibility of crank bolt loosening caused by:
- Engine vibration
- Harmonics
- Repeated high-load operation
- Increased power and torque
The result is a simple mechanical safeguard against crank bolt rotation.
T-6061 Billet Aluminium Capture Plate
The MMX Capture Plate is machined from T-6061 billet aluminium.
It is then anodised in MMX's gloss-black finish.
The design uses elongated mounting slots to help achieve accurate installation around the crank bolt.
Capture Plate with OEM or MMX Hub
The MMX Capture Plate can be used with:
- The factory crank hub
- The MMX single-piece crank hub
This means owners can fit the capture plate as a standalone precautionary upgrade or combine it with the MMX crank hub for a more comprehensive solution.
Crank Hub Only vs Crank Hub + Capture Plate
The MMX single-piece crank hub addresses the possibility of friction-plate slip within the original multi-piece hub design.
The Capture Plate addresses a separate issue by preventing the crank bolt itself from loosening.
For this reason, combining the two provides a more complete solution.
Crank Hub Only:
- Replaces factory multi-piece hub
- Eliminates friction-plate movement between hub sections
- Supplied with new crank bolt
- Suitable for standard and moderately tuned applications
Crank Hub + Capture Plate:
- Includes all crank hub benefits
- Adds physical crank bolt retention
- Provides an additional layer of security
- Ideal for performance-focused builds
Suitable for Stage 1 Tuned Cars
MMX states that its unpinned single-piece crank hub is more than sufficient for Stage 1 tuned N55 and S55 engines.
Because no locating pins need to be drilled into the crankshaft, installation is also less involved than with a pinned crank hub.
This makes the standard one-piece version particularly attractive for road and fast-road cars where reliability is the priority without requiring the additional complexity of crankshaft drilling.
MMX 4-Pin Crank Hub for Higher-Power Builds
For engines tuned beyond Stage 1 or producing significantly increased power and torque, MMX recommends its upgraded four-pinned single-piece crank hub.
The pinned version mechanically locks the hub to the end of the crankshaft using four locating dowels.
MMX part number for the four-pinned version is:
MMR20-1004
This is the more appropriate option for:
- Higher-power builds
- High-torque applications
- Aggressively tuned engines
- Dedicated track cars
- Motorsport use
One-Piece vs 4-Pinned Crank Hub
The standard MMX one-piece crank hub eliminates the slipping interface between the components of the factory multi-piece hub.
The four-pinned version goes further by mechanically locating the hub directly to the crankshaft.
Choose the standard one-piece hub for:
- Standard engines
- Stage 1 tuned cars
- Road-focused builds
- Simpler installation
Consider the four-pinned version for:
- Higher power levels
- Higher torque
- More aggressive tuning
- Track-focused builds
- Maximum mechanical security
Reliability-Focused Upgrade
A crank hub upgrade does not directly add power.
Its purpose is to improve reliability and provide additional confidence when the engine is operating under increased load.
It is particularly relevant for vehicles running:
- ECU tuning
- Increased boost
- Upgraded turbochargers
- Intake modifications
- Performance exhausts
- Track-focused setups
As engine output increases, improving supporting reliability becomes increasingly important.
Professional Installation Required
Crank hub replacement is a specialist mechanical job.
Correct engine timing must be maintained throughout installation.
Professional installation by a BMW specialist is strongly recommended.
The process requires:
- Access to the front of the engine
- Engine timing tools
- Correct crankshaft locking
- Correct torque procedure
- Careful reassembly
- Verification of engine timing
Incorrect installation can result in serious engine damage.
Capture Plate Installation
The MMX Capture Plate can also be fitted independently of the single-piece crank hub.
MMX states that installation can be carried out with the engine remaining in the vehicle, although additional access is required at the front of the engine.
This makes the standalone capture plate a more accessible preventative upgrade than a full crank hub replacement.
BMW F20 / F21 M135i
The MMX crank hub is compatible with applicable BMW F20 and F21 M135i models powered by the N55 engine.
For tuned or hard-driven M135i builds, it provides an important reliability-focused upgrade.
BMW F22 / F23 M235i
The N55-powered BMW F22 M235i Coupe and F23 M235i Convertible are also supported.
The crank hub can be particularly relevant on cars running increased boost or ECU tuning.
BMW F30 / F31 335i
The MMX crank hub is suitable for compatible N55-powered BMW F30 and F31 335i models.
It provides additional protection for standard, tuned and performance-focused builds.
BMW F32 / F33 435i
The N55-powered BMW F32 435i Coupe and F33 435i Convertible are also supported.
For modified cars, the single-piece crank hub provides a stronger foundation for future performance upgrades.
BMW F87 M2
The original BMW F87 M2 uses the N55 engine and is included within MMX's current application list.
For tuned or track-driven F87 M2 builds, improving crank hub security is a common reliability-focused modification.
BMW F87 M2 Competition
The BMW F87 M2 Competition uses the S55 engine and is also supported.
The same single-piece design helps eliminate movement between the components of the original multi-piece crank hub.
BMW F80 M3
The MMX crank hub is compatible with the S55-powered BMW F80 M3.
It is particularly relevant for cars running increased power or frequent track use.
BMW F82 / F83 M4
The BMW F82 M4 Coupe and F83 M4 Convertible are also supported.
For tuned S55 applications, the MMX crank hub and Capture Plate can form an important part of a reliability-focused engine build.
Compatibility
Designed for applicable BMW N55 and S55 models including:
- BMW F20 M135i
- BMW F21 M135i
- BMW F22 M235i
- BMW F23 M235i Convertible
- BMW F30 335i
- BMW F31 335i Touring
- BMW F32 435i
- BMW F33 435i Convertible
- BMW F87 M2
- BMW F87 M2 Competition
- BMW F80 M3
- BMW F82 M4
- BMW F83 M4 Convertible
MMX lists fitment across F2X, F3X, F80, F82 and F87 chassis with N55 and S55 engines.
Please confirm exact engine and vehicle specification before ordering.
What's Included?
MMX Single-Piece Crank Hub:
- MMX one-piece EN36 billet steel crank hub
- New crank bolt
- Required MMX-specific components
When selected with MMX Capture Plate:
- MMX one-piece crank hub
- New crank bolt
- MMX T-6061 billet aluminium Capture Plate
- Required mounting hardware
Exact kit configuration depends on the option selected.
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