KIES MOTORSPORTS, LLC — TERMS AND CONDITIONS OF PURCHASE AND SALE

The MMX Performance BMW N55 / S55 One-Piece Crank Hub Upgrade Kit is engineered to address the factory three-piece crank hub design found on BMW N55 and S55 engines. The factory assembly relies on friction surfaces between multiple components to maintain crankshaft timing, creating the potential for rotational slip under load.

The MMX one-piece crank hub replaces the factory multi-piece assembly with a single, integrated billet component. By eliminating the separate friction-based sections of the original hub, the MMX design removes the possibility of the hub components slipping independently of one another and provides a more robust foundation for maintaining crankshaft timing.

At the center of the upgrade is a CNC-machined crank hub manufactured from billet EN36 steel. The component is heat-treated with a 0.75mm case hardening to provide the surface hardness, strength, and wear resistance required for a critical engine timing component. A new crank bolt is also supplied with the kit for installation.

This unpinned one-piece configuration provides an important advantage for street-driven and moderately tuned BMW applications: installation does not require precision drilling of the crankshaft for locating dowels. MMX recommends this version for standard through Stage 1 tuned N55 and S55 engines, providing a significant upgrade over the factory three-piece design without the additional installation requirements of a pinned crank hub.

For additional crank bolt security, the system can be paired with the MMX Crank Hub Capture Plate. The billet aluminum capture plate mechanically secures the crank bolt head to help prevent loosening caused by engine vibration and harmonics.

For higher-output builds requiring an additional mechanical connection between the hub and crankshaft, MMX also offers a 4-pin version. The 4-pin system uses four precision-machined dowels to mechanically locate the hub to the crankshaft and is recommended by MMX for applications operating beyond the intended range of the standard one-piece upgrade.

Product Details

• MMX Performance one-piece crank hub upgrade for BMW N55 and S55 engines
• Replaces the factory three-piece crank hub assembly
• Single-piece construction eliminates internal friction-plate slip
• CNC-machined from billet EN36 steel
• 0.75mm case-hardened heat treatment
• Engineered for increased strength, wear resistance, and durability
• Includes new crank bolt
• Unpinned design does not require drilling the crankshaft for locating dowels
• Recommended by MMX for stock through Stage 1 tuned N55 and S55 applications
• Compatible with the MMX Crank Hub Capture Plate
• Professional installation required

Recommended Products

• MMX Performance BMW S55 / N55 One-Piece Crank Hub Upgrade Kit – 4-Pin
• MMX Performance BMW S55 / N55 Crank Hub Capture Plate