Shimano's Ultegra FC-R8000 Crankset represents true trickle down from Shimano's flagship Dura-Ace group not only visually, but in the technological features that make both cranksets light, stiff, and shift with precision. The new, aggressively angular lines increase stiffness, providing excellent power transfer. The chainrings and bolts were also redesigned to provide better chainstay clearance for shorter rear end bikes or road disc bikes with wider dropout spacing.
Shimano has the technical expertise and manufacturing prowess to create industry-leading shifting and stiffness to weight for the rings and crank arms, respectively. The latter property is owed to Shimano's Hollowtech II arm construction, a heavily guarded secret. Where other manufacturers drill the arms to reduce weight or create two sides and clam-shell them together, Shimano is able to forge the arms and still keep them hollow. As with the Dura-Ace 9100 series, Shimano adds some width to the R8000's arms and orients the spider to more efficiently transfer energy during important power phases throughout the pedal stroke. The asymmetric spider and chainring spacing allows Shimano to put two chainring bolts close to the wider arms, further adding rigidity to the rings for better shifting and power transfer.
As noted above, Shimano's excellent chainring engineering continues with the FC-R8000. We once heard a rumor that Shimano owns patents on every single chainring tooth's shape, pin, shift ramp, etc. We're not sure if this is true, but we do know that, compared to other rings we've used, Shimano rings in operation tend to run much quieter, wear at a much better rate, and offer more positive and quicker shifting.
The tooth profiles on this crank have been slightly altered to improve shifting and chain retention at the extreme chainlines seen on the shorter stays of newer bikes combined with larger cassette ranges and wider rear spacing. To lessen the chainline, the inner chainring has been brought in .4mm towards the bike, and specially designed chainring bolts ensure enough clearance between them and the chainstays. To optimize front shifting, Shimano recommends the new FD-R8000 front derailleur as it's designed for the new chainrings' placements and allows for proper frame clearance.
Features that have been on Shimano road cranks for years are still present in this design. A 24mm steel spindle is bonded to the drive side aluminum arm and is compatible with many frame and bottom bracket—ahem—standards. The non-drive arm slides onto the crank axle with splines and allows for a precise fit. The included crank fixing bolt adjusts bearing preload and the pinch bolts secure the arm to the spindle, and the Hollowglide chainrings are lightweight and super stiff. Similar to what Shimano has done on their mountain chainrings, the outer chainring is aluminum and bonded to a composite structure, increasing stiffness while decreasing weight.
The Ultegra FC-R8000 Crankset is offered in 4 different lengths and chainring combinations, so regardless of your fit or bike's requirements, you are covered. All chainring sizes work on the same proprietary asymmetric 4-arm spider, so changing out chainrings for different terrain, disciplines, or seasons is easy. We're once again blown away by the performance and value Shimano packs into its Ultegra cranksets and feel confident that this crank will serve us well for years with the flexibility to swap it between bikes if needed.