Bring precise, dual-sided power measurement to your road training with the Shimano Ultegra FC-R8100-P — a 2×12-speed crankset that pairs independent left/right power data with Ultegra's exceptional value. Whether you're dialling in training zones, chasing race-day watts, or working with a coach on pedal stroke efficiency, this crankset delivers the data you need from both legs simultaneously.

Highlights

• Dual-sided power measurement: independent left and right leg data gives you true total watts plus an accurate power balance percentage.
• ±2.0% accuracy: consistent, repeatable measurement across the full calibration range for reliable training and racing data.
• Active temperature compensation: maintains measurement accuracy across varying conditions, so heat or cold won't skew your numbers.
• Force vector data: visualise where in the pedal stroke you're generating force — a powerful tool for stroke efficiency coaching and bike fitting.
• 300+ hour rechargeable battery: integrated waterproof Li-ion battery eliminates coin cell hassle; charges via a standard port.
• ANT+ and Bluetooth Smart: broadcasts to dual protocols simultaneously, compatible with head units, smartwatches, and training apps.
• HOLLOWTECH II construction: hollow-forged aluminium crank arms deliver a stiff, lightweight platform for efficient power transfer.
• Hollowglide chainrings: engineered for fast, precise front shifting across all 12 speeds.

Power Meter Technology

The FC-R8100-P measures power directly from both crank arms, capturing each leg's output independently rather than doubling a single-sided reading. You get accurate total watts alongside a left/right power balance percentage, cadence, and force vector data that reveals exactly where in each pedal stroke you're producing — and losing — power. Active temperature compensation keeps the measurement stable whether you're riding in a hot Australian summer or an early-morning winter session.

Construction

Crank arms are built using Shimano's HOLLOWTECH II process — hollow-forged aluminium that removes material where it isn't needed while maintaining the rigidity essential for accurate force measurement. The 110 mm asymmetric 4-bolt BCD is shared with DURA-ACE R9200, meaning chainring upgrades are fully cross-compatible between groupsets. The integrated power meter electronics are fully waterproof and self-contained within the crank arms.

Compatibility & Fit

Designed for 2×12-speed road drivetrains. Compatible with Shimano Ultegra R8100/R8150 and DURA-ACE R9200/R9250 groupsets. Requires a 24 mm Shimano bottom bracket — SM-BBR60 for threaded shells (68/70 mm) or SM-BB72-41B for press-fit BB86/BB92 shells. Compatible with Ultegra and DURA-ACE front derailleurs. Chainline: 44.5 mm. Q-factor: 148 mm. BCD: 110 mm asymmetric 4-bolt. This listing is for the 175 mm crank arm length with 52/36T chainrings.