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BMW I S55 I N55


Why fit?

Failures caused by the standard three-piece crank hub on BMW’s S55 & N55 engines in M2C, M3 and M4, and M135i & M235i are (unfortunately) all-too well known, but these are fully addressed with the installation of the ultimate MMR Performance 4-Pin Single-Piece billet Crank Hub, together with the option of adding our Capture Plate for ultimate security.

Benefits of fitting?

MMR Performance now offers this uprated pinned version of our popular Single-Piece Crank Hub, with a 4-Pin dowelled location that locks onto the end of the crankshaft. The OE crank hub unit's friction plate are known to slip rotationally, causing the timing to alter enough that piston-to-valve contact can occur, leaving owners with a very expensive repair bill.

This 4-pin version of our Single-Piece Crank Hub kit is simply the ultimate solution to preventing this problem before it happens on high horsepower & torque engines.

The centrepiece of the MMR kit is the UK made CNC-machined one-piece crank hub, created from billet EN36 steel that's been heat-treated with a 0.75mm case hardening, making it incredibly strong and durable. Along with this comes four aerospace precision machined dowels that mechanicallylock the hub to end of the crank itself, plus a brand new OE bolt.

Installation of these dowels is certainly not a DIY job. But to make the job easier for the professionals, ensuring that the required crank modifications are made safely and accurately, the MMR kit also includes a full installation jig that includes a bolt-on drilling guide, a location bolt for this guide, plus an HSS rolled high speed Drill Bit.

Together, the Single-Piece design combined with the 4-Pin location ensures that there is now no way that the friction plates can ever slip. With the new OE crank bolt tightened appropriately, this delivers a transformational improvement in reliability versus the OE version.

Finally. as another option alongside the 4-Pinned Crank Hub, adding the MMR Capture Plate ensures that owners have complete peace of mind.

The Capture Plate removes the possibility for the crank bolt to be able to loosen with the engine's vibrations or harmonics. The Capture Plate is an additional billet aluminium hat that securely bolts over the entire head of the crank bolt, making it literally impossible for the bolt to come undone. Please select from the product option below at point of ordering to include a Capture Plate with your order.

For BMW M2C, M3 and M4 S55-engined cars running high power and torque tuning setups, and N55-powered M2, M135i, M235i, 335i & 435i cars, MMR have engineered the most comprehensive solution on the market and at one of the most compelling price points. Don't run high power without one!










S55 I N55


2011 - 2020

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Pinned vs Unpinned:

As MMR Performance offers two versions of the Single-Piece Crank Hub, which is best for you, pinned or unpinned? For most standard to Stage 1 tuned S55 & N55 engines, the unpinned MMR Single-Piece Crank Hub (MMR20-1001) is more than sufficient. Installation is more straightforward as the end of the crankshaft does not need to be precision drilled to mount the four locating dowels. However, for high power/torque engines tuned beyond this level, we recommend this upgraded pinned version of the Crank Hub that incorporates the 4-pin dowel drive mounting for the ultimate engine security.

Whether Pinned or Unpinned, the MMR Crank Hub kit can be ordered in two formats. The Single-Piece Crank Hub can be selected on its own, or for best protection, choose the Crank Hub together with our billet Capture Plate. Our recommendation is always that if you're replacing the crank hub, you may as well add in the Capture Plate for the best possible future protection.

Please select your required option when ordering.

Fitting note:

Installation of a replacement Crank Hub and/or Capture Plate is a significant task, and should always be left to professional technicians.

This is particularly important for this pinned Crank Hub. The MMR kit includes a full installation jig, helping the installer to ensure that the all-important crank modifications are perfectly carried out. The install jig includes a bolt-on drilling guide, a location bolt for this guide, plus an HSS rolled high speed Drill Bit.

S55 and N55 crank bolt torque – 100Nm initial torque plus 270 degrees.

Note that if your factory Crank Hub has already shown any signs of slippage, you will have no choice but to replace it - once slipped there is no repair possible.

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How we develop.

Every MMR Performance upgrade is developed and tested here in the UK by our expert engineering team of BMW enthusiasts.

Nothing gets the MMR logo until we've thoroughly proven it on road, track and dyno.

That's the MMR Performance difference.


How to buy?

Our network of expert MMR Performance dealers can supply the full range, together with product guidance and advice, plus often an experience fitting service.


If you haven't got a MMR Performance Partner Dealer close to you, don't worry! Remember you can buy direct from our MMR Performance webshop. Click here to browse and shop online, for worldwide despatch.


Prefer to buy online?

You can buy direct from our MMR Performance webshop. Click here to browse and shop online, for worldwide despatch.

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