MMR 4-Pinned crank hub & capture plate | BMW S55 | N55

Description

The MMR 4-Pinned Single-Piece Crank Hub kit is a high-strength performance upgrade for BMW S55 and N55 engines designed to completely eliminate a known failure point in the factory crank hub. The standard multi-piece crank hub on these engines is prone to slipping under high boost or torque, which can cause the engine’s timing to change and lead to piston-to-valve contact — resulting in extremely costly engine damage.

This upgraded crank hub is machined from billet EN36 steel with case-hardening, making it significantly stronger and more durable than the OEM unit. It features four aerospace-precision dowels that mechanically lock the hub to the end of the crankshaft, preventing any rotational slippage. The kit also includes a full installation jig with drilling guide and high-speed drill bit to assist professional fitting.

For even greater security, an optional capture plate can be included to prevent the crank bolt from loosening under vibration. This combination provides a robust reliability upgrade for high-power engines and helps protect against catastrophic crank hub failure.