Shimano GRX RX810/RX820 PRECISION 3+ Left-Side Power Meter

What Our Gearhead® Experts Are Saying:

"I recommend this for riders building a gravel or endurance setup around GRX. The accuracy is spot on, and the left-side system keeps weight and cost down without sacrificing meaningful data. Battery life is long enough that I rarely think about it, and connectivity has been rock solid."

Modern gravel and endurance builds demand precise data without unnecessary complexity. The GRX RX810/RX820 PRECISION 3+ Left-Side Power Meter from 4iiii integrates directly into Shimano GRX cranksets, delivering professional-grade accuracy in a lightweight, crank-based platform optimized for mixed-terrain riding. This non-drive side system measures left-leg output and calculates total power with +/-1% accuracy, supported by automatic terrain selection to maintain consistency across changing gradients and surfaces. It transmits power, cadence, and calorie data via both ANT+ and Bluetooth Smart, ensuring compatibility with a wide range of head units, indoor training platforms, and adaptive coaching apps. With a power range of 0–4,000 watts and cadence support from 30–170 rpm, it accommodates everything from steady endurance efforts to high-RPM sprint intervals.

The Ride Ready configuration comes factory-installed on a Shimano GRX FC-RX810 or RX820 left crank arm, simplifying installation and preserving drivetrain compatibility. An 800-hour CR2032 battery minimizes downtime, while the IPX7 waterproof rating supports year-round riding in wet and variable conditions. Integrated Apple Find My technology enhances bike security when off the road. Ideal for gravel racers, endurance riders, and data-focused cyclists, this power meter delivers accurate performance tracking in a streamlined GRX-specific package.