Small parts have a way of becoming big problems at the worst moment—usually when you're reassembling a crankset the night before a ride and realize the plastic preload bolt is stripped or cracked. The Y1N218000 is Shimano's second-generation crank arm fixing bolt for Dura-Ace, the black plastic preload cap that threads into the end of the non-drive-side crankarm and sets bearing preload on Hollowtech II cranksets. It replaces the earlier A-Type (8.5mm thread depth) with a longer 16mm thread engagement, which is what current Dura-Ace cranks require.

Compatibility matters here because the two versions are not interchangeable. This B-Type 16mm bolt fits Dura-Ace FC-9000 cranksets manufactured after June 1, 2013, and also serves as the correct preload bolt for the follow-on FC-R9100 11-speed crankset. The earlier A-Type bolt with 8.5mm thread length is for FC-7900 and pre-June-2013 FC-9000 cranks—if you install an A-Type into a crank that needs the B-Type, you won't get enough thread engagement to properly set preload, and the bolt can back out under load.

Installation is standard Hollowtech II procedure. Slide the non-drive crankarm onto the splined spindle, thread this preload bolt in by hand using the Shimano TL-FC16 or TL-FC18 preload tool, and snug it just enough to remove lateral play at the bearings—typically 0.5 to 0.7 Nm, which is barely more than finger tight. The two 5mm pinch bolts on the crankarm are what actually clamp the arm to the spindle; this bolt only sets preload. Overtightening it is the most common mistake and the fastest way to crack the plastic head.... Read More