The Favero Assioma PRO RS represents the latest evolution in pedal-based cycling power measurement. Building on the success of Favero’s Pro MX mountain-bike variant, the PRO RS integrates proven electronics into a road-specific pedal body, promising durability, precision, and versatility. This deep-dive examines the technology underlying pedal-based power meters, evaluates Favero’s implementation of 3D scanning and multi-sensor strain analysis, and compares the PRO RS against competing systems in terms of accuracy, reliability, and real-world performance.

Pedal-Based Power Meter Fundamentals

Power meters convert the mechanical forces a rider applies into digital data. Traditional crank-arm or spider-based units measure pure torsional strain at a fixed location and calculate power as torque × angular velocity. Pedal-based systems, by contrast, must infer torque from strain gauges positioned on the pedal spindle, then multiply by crank length and rotational speed.

The Challenge: Torsion vs. Bending

• Spider-based meters measure shear strain directly on the spider, yielding a “pure” torsion signal
• Pedal meters measure bending moments and must correct for off-center loads to avoid erroneous torque readings
• Role of PCO: “Pedal Center Offset” quantifies where along the pedal spindle the rider’s force is applied

If an athlete’s foot applies force too far outside the spindle’s neutral axis due to unique biomechanics, unaccounted bending and torsional moments can introduce errors. Accurately resolving PCO is therefore vital for any pedal-based system that aims for ±1% accuracy.

Favero’s Proven Electronics and 3D Scanning Technology

The PRO RS uses the same spindle and electronic internals that have been field-tested on the Pro MX for over two years. Riders familiar with the mountain-bike version can attest to its robustness under harsh off-road conditions.

Design Excellence Through 3D Scanning

Favero employed 3D scanning of Shimano’s Ultegra R8000 pedal to ensure identical specifications:

• Stack height: 10.5mm (identical to Shimano Ultegra/Dura-Ace)
• Q-factor: +53mm (matches Shimano stock models)
• Weight: 123g per side (within tolerance of Ultegra R8000’s ~122.5g)

All strain gauges, gyroscopes, and battery components are housed entirely within the spindle—no bulky pods protrude from the pedal body. This internal-axle design protects electronics from impacts and ingress without increasing stack or weight.

Performance Specifications

• Battery Life: Over 60 hours of ride time per charge
• Data Transmission: ANT+ and Bluetooth 5.0
• Cadence Range: Up to 250 rpm
• Dual-side measurement: PRO RS-2 (left and right sensors)
• Single-side option: PRO RS-1 (left-only)

Solving the PCO Challenge: Advanced Strain Gauge Technology

A major challenge for pedal-based meters is accurately resolving PCO under varied foot positions. When riders place force outside the spindle’s neutral plane—common when pushing from the toe or heel—a net torque “parasite” arises that some systems cannot fully compensate.

Dual-Pair Strain-Gauge Layout

Favero uses at least two pairs of strain gauges on opposing faces of the spindle. By measuring differential bending between these gauges, the electronics solve for both total force and application point along the spindle. This Wheatstone-bridge configuration enhances common-mode rejection, meaning out-of-plane torque from off-axis pushes is largely canceled before final power computation.

Practical Impact: Laboratory and field tests demonstrate the PRO RS can report PCO values up to +53mm without significant drift or side-specific bias. Athletes with unusual biomechanics who regularly exhibit PCOs of 20-30mm see consistent left/right balance even when torquing the pedal edge.

Bearing Engineering: Precision Under Load

Beyond strain-gauge design, bearing construction plays a crucial role in measurement fidelity. Unwanted axial or radial play can create micro-shifts that mimic strain, especially under high loads.

Sealed Needle Roller Bearings

The PRO RS employs sealed needle roller bearings—two per pedal—on the inboard and outboard sides:

• Radial float: Approximately 0.12mm out of the box
• Durability: No change in radial play after 150+ hours of use
• Comparison: Shimano Ultegra R8000 exhibits ~0.13mm after 650 hours

The factory preload strikes a balance between minimal play and longevity. In practical riding, radial float of ≤0.12mm is imperceptible, even under sprint and standing-climb loads.

Real-World Performance Validation

Independent testing compared PRO RS data against crank-based systems (Quarq DZero, SRM, Stages) and other pedal meters (Look, Garmin Rally):

Sprint and Peak Power Testing

• Peak torque alignment: Within ±2% of SRM and Quarq units
• Sprint accuracy: <15W difference on 1000W sprints
• Transient response: Excellent tracking of power spikes <1 second

Sustained Effort Analysis

• 1-5 minute intervals: Power curves overlay almost identically with Quarq
• Single-leg tests: Negligible left/right bias (<0.5%)
• PCO tolerance: Consistent readings with lateral shifts up to 30mm

Durability Testing

Riders have logged over 2 years of off-road use on Pro MX spindles (identical electronics) with no calibration drift or failure, despite heavy impacts on gravel descents.

Competitive Analysis

How does the PRO RS stack up against the competition?

Spider/Crank-Based Systems

Quarq DZero, Shimano Dura-Ace FC-R9100-P, SRM X-POWER: Remain popular for straightforward torsion sensing but lack pedal portability—crank sets are bike-specific and require tools to swap.

Competing Pedal Systems

Model	Weight	Stack Height	Q-Factor	Key Issues
Favero PRO RS	123g	10.5mm	+53mm	None significant
Look Keo POWER II	~140g	~11mm	+55mm	Unreliable PCO compensation
Garmin Rally RS	153-200g	+12mm	+54mm	Bluetooth dropouts reported
Pioneer PD-9100P	150g	13mm	+56mm	Bulky battery pods

Technical Advantages Summary

The PRO RS’ unique combination of features positions it at the top of the pedal power meter class:

• Lightest in class: 123g per pedal
• Minimal stack compromise: 10.5mm (matches Shimano)
• Robust PCO resolution: Accurate up to 53mm offset
• Proven durability: 2+ years field testing on Pro MX platform
• Excellent accuracy: ±1% across all testing scenarios
• Extended battery life: 60+ hours per charge

Who Should Consider the PRO RS?

The Favero Assioma PRO RS is ideal for:

• Multi-bike riders who want easy power meter portability
• Weight-conscious cyclists seeking minimal compromise
• Athletes with unique biomechanics requiring accurate PCO resolution
• Training-focused riders demanding consistent, reliable data
• Gravel and adventure cyclists needing proven durability

The Verdict: Engineering Excellence at Its Peak

The Favero Assioma PRO RS represents a technical tour de force in pedal-based power measurement. By transplanting proven Pro MX electronics into a Shimano-compatible road pedal body and leveraging precise 3D scanning, the PRO RS delivers:

• Seamless integration with existing bike setups
• Laboratory-grade accuracy in real-world conditions
• Uncompromising durability for year-round training
• Advanced metrics without complexity

While top-tier track athletes seeking multi-kilohertz output rates may prefer specialized units, for most road cyclists, the PRO RS represents the pinnacle of power meter engineering. Its plug-and-play portability, minimal weight/stack compromise, and robust accuracy make it a standout choice for everything from winter training rides to crucial race efforts.

Future Outlook

As pedal-based technology continues evolving, Favero’s commitment to continuous firmware updates and proprietary IAV (Instantaneous Angular Velocity) algorithms suggests even tighter accuracy margins and extended battery life on the horizon. For now, the Assioma PRO RS stands as the benchmark in pedal power, delivering reliability, precision, and a seamless user experience that represents true engineering excellence in this competitive field.