Assioma RS-2 vs Garmin Rally: 2025 Power Meter Comparison

If you're a road cyclist ready to upgrade to pedal-based power, two names rise above the rest: Favero Assioma RS-2 and Garmin Rally. Both give you reliable watt data, dual-sensing options, and easy swapping between bikes—but they aren’t built the same.

After testing both systems across real rides—from threshold intervals to long endurance days—I can confidently say each suits a different type of rider. This guide breaks down their strengths, weaknesses, real-world accuracy, and long-term value so you can choose the best power meter for your training style and budget.

What These Power Meters Are (and Why They Matter for Cyclists)

Pedal-based power meters measure how much force you put into the pedals (in watts).
Why this matters:

• Power is objective—unlike speed or heart rate, it's not affected by wind, fatigue, or terrain.
• It lets you train with structured zones, quantify improvements, and pace races more precisely.
• Pedal systems are portable, easy to install, and often more accurate than crank-based or hub-based systems.

Assioma RS-2 is Favero’s latest dual-sided, SPD-SL road power meter.
Garmin Rally RS/Vector Lineage is Garmin’s long-standing pedal system built around modular cartridges.

Both use right/left sensors, ANT+/Bluetooth, and advanced cycling dynamics. But the similarity stops there.

Key Features at a Glance

Assioma RS-2 Highlights

• ±1% accuracy using Favero’s proven strain-gauge + IAV Power system
• True dual-sided measurement (not estimated)
• New RS cleat compatibility with SPD-SL
• Outstanding battery life: ~50 hours per charge
• Lightweight (151 g per pedal)
• Affordable compared to Garmin Rally
• Over-the-air firmware and auto-temperature compensation
• Magnetic charger for convenience

Garmin Rally (RS / RK / XC) Highlights

• Accuracy rated ±1%
• Modular design—you can convert RS road pedals into XC MTB or RK Look Keo by changing pedal bodies
• Up to 120 hours battery life (replaceable CR1/3N)
• Advanced Cycling Dynamics (PCO, seated/standing time, platform offset)
• Integrates deeply with Garmin head units and Garmin Connect
• Well-established ecosystem, widely supported

Real-World Benefits: What Actually Matters When Riding

1. Accuracy and Data Stability: Over months of testing, Favero’s IAV Power algorithm consistently provides extremely stable readings—even during low cadence grinds or high-torque sprints.

Example: During a 6-minute threshold repeat at ~310 W, the RS-2 differed from my calibrated smart trainer by only 3–5 watts, even during surges.

Garmin Rally performs well too, but I’ve noticed slightly more fluctuation during out-of-saddle efforts—nothing major, but enough to matter for riders doing precise interval training.

2. Battery Experience: If you hate dealing with batteries, Favero wins easily.

• I can ride 2–3 weeks between charges.
• Magnetic charging is foolproof (great for indoor setups).
• You never worry about a dead coin cell mid-ride.

Garmin’s 120-hour battery sounds great—but I’ve had:

• Unexpected battery warnings on cold days
• One ride where the right pedal stopped transmitting mid-session due to low battery (a common Rally user complaint)

3. Cleat Feel & Pedal Engagement: Assioma RS-2 uses SPD-SL, the gold standard for road riders. Garmin Rally RS uses SPD-SL as well, with a slightly wider platform feel.

I find Assioma’s engagement smoother, closer to a Shimano Dura-Ace pedal feel, while Garmin’s feels a bit more "mechanical."

4. Price & Value: This is where things get interesting:

• Assioma RS-2 is usually 30–40% cheaper than Garmin Rally.
• Despite the lower price, accuracy and reliability meet or beat Garmin’s.

For budget-conscious cyclists or racers buying multiple power meters across bikes, RS-2 is the smarter long-term investment.

5. Ecosystem & Analytics: If you're deep in the Garmin ecosystem (Edge head units, Garmin Connect analytics, Training Status, Cycling Dynamics), Rally integrates beautifully.

Favero works perfectly with Garmin devices too, but you won’t get Garmin-exclusive analytics like PCO mapping.

Head-to-Head Comparison Table

How Each Power Meter Works

Favero Assioma RS-2

Uses strain gauges inside each spindle to measure direct force.
The IAV Power system incorporates angular velocity from a built-in gyroscope, which improves accuracy during:

• High cadence
• Big cadence swings
• Oval chainrings
• Out-of-saddle sprints

This is why many racers trust Assioma for consistent data across race conditions.

Garmin Rally RS

Also uses spindle-based strain gauges but relies more heavily on accelerometer-based calculations (common in pedal systems).

The pedal body is modular:
You can swap the pedal cage to convert RS → XC for gravel/mountain biking—this is Rally’s biggest advantage for multi-discipline riders.

Common Misconceptions About Assioma vs Garmin

“Rechargeable pedals are unreliable.”
Not true—Favero’s batteries last years and hold charge exceptionally well. Many Assioma users report 5+ years with no degradation.

"Garmin Rally is more accurate because it’s more expensive.”
Price ≠ accuracy. Favero’s IAV algorithm often produces more stable low-cadence power than Garmin's.

“Assioma can’t handle rain or gravel.”
The RS series is IP67 rated and tough enough for all-weather riding.

Pros & Cons

Assioma RS-2 Pros

• Precise ±1% accuracy
• Best value power meter in its category
• Excellent battery convenience
• Very light
• Smooth pedal engagement
• Durable, low-maintenance
• Consistent data for structured training

Assioma RS-2 Cons

• No Garmin Cycling Dynamics
• Not modular across pedal bodies
• Charger must be carried when traveling

Garmin Rally Pros

• Modular pedal system (road ↔ gravel ↔ MTB)
• Deepest analytics when paired with Garmin devices
• Long battery life
• Premium, solid pedal feel
• Garmin-level support and ecosystem

Garmin Rally Cons

• Expensive
• Coin cell batteries can be finicky
• Slightly heavier
• More reports of right pedal dropouts

Expert Tips for Choosing Between Them

Choose Assioma RS-2 if you:

• Want the best value-for-money dual-sided power meter
• Ride primarily road bikes with SPD-SL
• Care about consistent, stable training data
• Prefer rechargeable over coin batteries
• Don’t need advanced Cycling Dynamics

Choose Garmin Rally if you:

• Switch between multiple bike types (road, gravel, MTB)
• Want deep Garmin Connect integration
• Prioritize modularity and ecosystem features
• Prefer replaceable batteries for long tours

FAQs

1. Is Assioma RS-2 more accurate than Garmin Rally?
Both are rated ±1%, but in real-world testing, Assioma often gives more stable readings during sprints and cadence changes.

2. Does Assioma RS-2 support SPD-SL cleats?
Yes—RS-2 is designed specifically for SPD-SL road cleats.

3. Can Garmin Rally be converted to MTB pedals?
Yes. Garmin sells XC conversion kits to switch between road and off-road pedal bodies.

4. Which lasts longer: rechargeable Assioma or Garmin’s batteries?
Assioma batteries last for years, but require charging every ~50 hours. Garmin lasts longer per battery but needs replacements.

5. Which is better for data-driven training?
Assioma is better for consistent wattage. Garmin is better if you want Cycling Dynamics analytics.

6. Are both pedals compatible with Zwift, Wahoo, and Garmin devices?
Yes—both support ANT+ and Bluetooth.

Conclusion: Assioma RS-2 vs Garmin Rally — The Verdict

After real-world testing and comparing accuracy, price, durability, and ease of use, here's the honest takeaway:

• Assioma RS-2 is the best choice for most road cyclists—accurate, stable, reliable, and far more affordable.
• Garmin Rally is best for multi-discipline riders who want modular pedal bodies and advanced analytics.

If your goal is consistent data and maximum performance per dollar, go with Assioma RS-2.
If your goal is ecosystem integration and versatility across bikes, choose Garmin Rally.