MMR 4-Pin Single Piece Crank Hub – BMW S55/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.
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.
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.
