MMR MMX Performance 4-Pinned Single Piece Crank Hub for BMW N55 & S55 MMR20-1004

Single-piece crank hub with a 4-pin dowelled location that locks onto the end of the crankshaft.

The centrepiece of the MMR kit is the UK made CNC-machined one-piece crank hub, created from billet EN36 steel that's heat-treated with a 0.75mm case hardening, making it incredibly strong and durable. Included are 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 four-pin location ensures that there is simply no way that the friction plates can ever slip. With the new OE crank bolt tightened appropriately, this delivers a transformational improvement in reliability and peace of mind versus the OE version.

Engine failures caused by the standard three-piece crank hub on the S55 and N55 engine are (unfortunately) well known, but these are fully addressed with the installation of the MMR Performance 4-pinned single-piece crank hub. Together with the option of adding our Capture Plate for ultimate security.

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.

Our 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 engines.