The Shimano Ultegra FC-R8100-P delivers factory-integrated dual-sided power measurement for serious road riders who want accurate watt data from both legs without the compromise of aftermarket add-ons. Built on the same Hollowtech II platform as the standard Ultegra crankset, it brings Dura-Ace-level power meter technology to a more accessible price point — this 175mm variant ships without chainrings so you can pair your preferred ring combination separately.

Highlights

• Dual-sided measurement: 24 strain gauges (12 per crank arm) capture independent left and right leg power for complete balance data.
• ±1.5% accuracy: Active temperature compensation keeps readings consistent from cold winter mornings to summer crits.
• ANT+ and Bluetooth LE: Broadcasts simultaneously to head units, smartphones, and training apps.
• 300+ hour battery: Integrated rechargeable lithium-ion cell charges in approximately 2.5 hours via the EW-EC300 port — compatible with Ultegra Di2 charging cables.
• Hollowtech II construction: Hollow-forged aluminium alloy crank arms with a 24mm chromoly spindle integrated into the right arm for outstanding stiffness-to-weight efficiency.
• No chainrings included: Fits Shimano 110mm asymmetric 4-bolt BCD chainrings — choose your own ring combination (50/34T, 52/36T, or 53/39T).
• Pedalling dynamics: Reports power balance, pedal smoothness, torque effectiveness, and cadence — pairs with Shimano Connect Lab for in-depth analysis.

Power Meter Technology

Twenty-four strain gauges bonded across both crank arms measure the forces applied through each pedal stroke with ±1.5% claimed accuracy. Active temperature compensation continuously adjusts calibration so power readings stay reliable regardless of conditions. Zero-offset calibration is quick and simple via a switch on the transmitter. Cadence is measured independently on each side, and all data — power, left/right balance, torque effectiveness, pedal smoothness — broadcasts simultaneously over ANT+ and Bluetooth Smart so you can run a head unit and a training app at the same time.

Hollowtech II Construction

Shimano's Hollowtech II platform positions the bottom bracket outboard of the frame shell, shortening the spindle span and increasing torsional stiffness through the drivetrain. The 24mm chromoly spindle is integrated into the right crank arm and passes through the bottom bracket shell; the left arm is then secured with a pinch bolt — a familiar, reliable fitment for riders and mechanics alike. The hollow-forged aluminium alloy arms optimise the stiffness-to-weight ratio without adding unnecessary mass.

Compatibility & Fit

This crankset ships without chainrings and accepts Shimano 110mm asymmetric 4-bolt BCD rings (50/34T, 52/36T, or 53/39T). Compatible with Shimano R8100 Ultegra and R9200 Dura-Ace 2×12-speed front derailleurs. Requires a Shimano Hollowtech II bottom bracket: SM-BBR60 (68mm BSA threaded) or SM-BB72-41B (PF86/41mm press-fit) — sold separately. Chainline is 44.5mm; Q-factor is 148mm; spindle diameter is 24mm. Designed for 130mm OLD rear axle spacing. Crank arm length: 175mm.