MMR Crank Hub 4-Pinned Single Piece Upgrade - BMW / S55 / N55

Engine failures caused by the standard three-piece crank hub on the S55 & N55 engine are (unfortunately) well known, but these are fully addressed with the installation of the MMR Performance 4-Pinned Single-Piece billet Crank Hub, together with the option of adding our Capture Plate for ultimate security.

MMR Performance now offers this uprated 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 centerpiece 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 mechanically lock 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.

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 (MMR20-1003) 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.



OE Multi-Piece Crank Hub (L) compared to MMR Single Piece Crank Hub (R) 

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 aluminum 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.



Single-Piece Crank Hub (L) with Capture Plate (R)

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

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!