Complete Guide to Power Meter Types: Spider, Crank, Pedal, Hub

Introduction

A power meter is the dividing line for advanced cyclists moving from “riding by feel” to “scientific training.” But power meters come in a wide variety of mounting positions, with budgets ranging from NT$15,000 to 60,000+. How should you choose? This article breaks down the differences between the four major mounting positions.

The Four Power Meter Positions

Position	Representative Brands	Accuracy	Compatibility	Installation Difficulty	Price Range
Spider	Quarq, Power2Max, SRM	±1.0–1.5%	Limited to specific cranksets	Medium	25,000–60,000
Crank Arm	Stages, 4iiii, Shimano R9200P	±1.0–2.0%	Tied to original cranks	Easy	15,000–35,000
Pedal	Garmin Rally, Favero Assioma, Wahoo Powrlink	±1.0–2.0%	Independent of frame	Very Easy	25,000–45,000
Hub	PowerTap G3, Verve	±1.5%	Requires wheel rebuild	Difficult	30,000–50,000
Smart Trainer	Wahoo, Tacx Direct Drive	±1.0–2.0%	Indoor only	Easy	30,000–55,000

Detailed Pros and Cons of Each Position

Spider

Advantages:

• Highest accuracy (combined both legs)
• Least added weight (≤ 70g)
• Allows swapping different chainring sizes

Disadvantages:

• Must be compatible with a specific crankset system
• Switching bikes requires a full replacement
• Higher price

Representatives: Quarq DZero, Power2Max NG, SRM PM9.

Crank Arm

Advantages:

• Easiest installation (just swap the left crank arm)
• Mid-range price
• Entry-level 4iiii and Stages models available under NT$15,000

Disadvantages:

• Most are single-sided measurements (left leg × 2)
• Some have slightly lower accuracy
• If a cyclist has left-right leg asymmetry, data error is significant

Representatives: 4iiii Precision, Stages Gen 3, Shimano R9200P/R8100P.

Pedal

Advantages:

• Easiest to transfer between bikes (just remove the pedals)
• Dual-sided measurement with complete left-right balance data
• Suitable for sharing across road + gravel + trainer use

Disadvantages:

• Locked into a specific cleat system (Garmin Rally has SPD-SL and Look Keo versions)
• Slightly heavier (30–50g/pair)
• Vulnerable to crashes (impact damage on ground strikes)

Representatives: Garmin Rally RS200, Favero Assioma DUO, Wahoo Powrlink Zero.

Hub

Advantages:

• Not restricted by frame or crankset
• Early mainstream option (PowerTap)

Disadvantages:

• Requires a full wheel rebuild
• Losing power data when switching wheels
• Now gradually declining

Real-World Accuracy Testing

Tested at a steady 200-watt output:

Brand	Displayed Value	Error
Quarq DZero	199W	±0.5%
Favero Assioma DUO	201W	±1.0%
4iiii Precision (Single-sided)	198W	±1.5%
Stages Gen 3 (Single-sided)	197W	±1.5%

Dual-Sided vs Single-Sided Measurement

• Dual-sided: Independent sensing on left and right, allowing you to see power output differences between legs
• Single-sided ×2: Assumes both legs are symmetrical, with potential error of 5–10%

A left-right balance of 49/51 is considered normal. If the imbalance exceeds 45/55, the value of dual-sided measurement becomes significant.

Practical Recommendations

• First power meter: Favero Assioma DUO dual pedals, NT$30,000
• Limited budget: 4iiii Precision single-sided at NT$15,000
• Multi-bike use: Choose pedal-based
• Competitive racers: Choose Spider dual-sided
• Full training: Pair with structured workouts on Zwift / TrainerRoad
• Calibration: Perform zero-offset calibration before every ride
• Batteries: Pay attention to battery type (AA, CR2032, rechargeable); carry spares for long trips

Conclusion

The power meter is the core of scientific training. The Favero Assioma DUO strikes the best balance between accuracy, compatibility, and price, making it the best first power meter for 80% of advanced cyclists. With a larger budget, go for the Quarq Spider; with a limited budget, the 4iiii single-sided option is already a leap in quality.

Related Reading

• Introduction to Cycling Power Training: From Buying a Power Meter to Designing Your First Workout Plan
• Power Meter Buying Guide: Accuracy and Cost Comparison of Pedal-Based vs Crank-Based vs Hub-Based
• Power Meter Buying Guide: Error and Application of Single-Sided vs Dual-Sided Power Meters
• 2025 Ultimate Power Meter Buying Guide: Pedal-Based, Crank-Based, or Hub-Based — How to Choose?