Precision Dynamics S55 M3/M4/M2C and N55 1 Piece Keyway Crank Hub

    Overview Our 1-piece crank hub design eliminates the possibility of a crank hub from spinning. We designed our crank hub to have a keyway, with a higher shear strength over dowel pin designs.    Why do you need this product? The S55, whether stock or modified, has a possibility of crank hub failure. The OEM crank hub is a 3 piece design, utilizing friction disc to retain engine timing together. The friction disc depends on clamping force to clamp down the pieces of crank hub together. As the engine rotates counter clockwise, over time the crank bolt slowly backs out and loses its clamping force. This will cause engine timing to spin out of position. With enough load, engine timing can significantly be out of timing, causing the intake valves to hit against the engine piston. Severe Crank Hub failure such as this will require replacements of intakes valves, which will be a very expensive repair. We recommend to perform a crank hub service as preventative maintenance. While not all