The Shimano Ultegra FC-R8100 brings flagship-grade shifting precision and power transfer to the dedicated road cyclist. Engineered as the drivetrain foundation for the 12-speed R8100 groupset, it pairs HOLLOWTECH II stiffness with HOLLOWGLIDE chainring technology for front shifts that are faster, quieter, and more reliable across the full range of cadence and gradient.

Highlights

• HOLLOWTECH II hollow crank arms — exceptional stiffness-to-weight ratio for direct power transfer
• HOLLOWGLIDE chainrings — precisely profiled teeth for rapid, low-friction chain engagement and release
• Outboard bottom bracket bearing system — wider stance for improved pedalling stability and efficiency
• 24mm hollow steel axle — integrated with the right crank arm for maximum rigidity
• Available in three chainring combinations: 50/34T (compact), 52/36T (semi-compact), 54/40T (standard)
• Crank arm lengths from 160mm to 175mm — accommodates a wide range of rider builds and fit preferences
• Q-factor: 148mm | Chainline: 44.5mm | BCD: 110mm
• Weight: approx. 700g (50/34T, 170mm) / 711g (52/36T, 170mm)

HOLLOWTECH II & HOLLOWGLIDE Technology

HOLLOWTECH II integrates the 24mm hollow axle directly into the right crankarm, pushing the bottom bracket bearings outboard of the frame shell. This widens the effective bearing span, reducing flex under load and delivering a stiffer, more responsive pedalling platform. The HOLLOWGLIDE chainrings feature optimised tooth profiles — working in concert with Shimano's 12-speed HG+ chain — to smooth engagement at every point in the chainring's rotation and enable crisp, positive front shifts whether you're sprinting or grinding.

Part of the Ultegra R8100 Ecosystem

The FC-R8100 is designed to work seamlessly within the full Shimano Ultegra R8100 12-speed groupset, including the FD-R8150 Di2 electronic front derailleur and RD-R8150 Di2 rear derailleur. The 44.5mm chainline and 110mm BCD are shared with DURA-ACE R9200, meaning chainring swap compatibility across the two groupsets. The crankset is sold without a bottom bracket — pair it with the SM-BBR60 (threaded) or SM-BB72-41B (press-fit) to suit your frame.

Compatibility & Fit

The FC-R8100 is compatible with Shimano 12-speed R9200 and R8100 drivetrains. It requires a Shimano-compatible bottom bracket for a 24mm axle: SM-BBR60 for threaded (68mm or 70mm shell) or SM-BB72-41B for press-fit frames. Recommended front derailleurs are the FD-R9250 or FD-R8150. Compatible chains include Shimano CN-M9100, CN-M8100, CN-M7100, and CN-M6100 (12-speed). Not compatible with 11-speed or earlier drivetrains.