Complete Comparison of Road Bike Power Meter Types: Pedal, Crank Arm, Spider, and Hub-Based

Complete Comparison of Road Bike Power Meter Types

A power meter has become an essential tool for serious road cyclists in training. Yet the market offers many different types—pedal, crank arm, spider, and hub-based units—each with its own measurement principle and ideal use case. This article takes a deep dive at the component level to break down the technical differences between them.

The Basic Principle of Power Measurement

At the core of every power meter is a strain gauge, which measures tiny deformations in a material to calculate the applied force. That force is then combined with angular velocity to derive power:

Power (W) = Torque (Nm) × Angular Velocity (rad/s)

What sets the different power meter types apart is where the strain gauge is mounted, and this directly affects measurement accuracy, reliability, and overall user experience.

1. Pedal-Based Power Meters

Representative products: Favero Assioma, Garmin Rally, Wahoo Speedplay Powrlink

Measurement Location and Principle

The strain gauge is mounted inside the pedal spindle, measuring the bending moment and torque the spindle experiences during pedaling.

Technical Specification Comparison

Product	Accuracy	Battery	Weight (dual-sided)	Cleat System	Suggested Retail Price
Favero Assioma DUO	±1%	Built-in rechargeable	~300g	Look Keo	NT$28,000
Favero Assioma DUO-Shi	±1%	Built-in rechargeable	~310g	Shimano SPD-SL	NT$32,000
Garmin Rally RK200	±1%	Replaceable CR1/3N	~320g	Look Keo	NT$32,000
Garmin Rally RS200	±1%	Replaceable CR1/3N	~336g	Shimano SPD-SL	NT$32,000

Advantages

• Easiest installation: Simply swap the pedals—works on virtually any bike
• Fully portable across bikes: Moving between multiple bikes takes only minutes
• Dual-sided measurement is common: Most products offer independent left/right measurement

Disadvantages

• Limited pedal choice: You must use the cleat system tied to that specific brand
• Q-factor impact: Some products increase Q-factor (the distance between the feet)
• Ground clearance: Pedal body size can affect lean angle when cornering

2. Crank Arm-Based Power Meters

Representative products: Stages, 4iiii Precision, Shimano OEM power crank

Measurement Location and Principle

The strain gauge is bonded directly to the inner or outer surface of the crank arm, measuring the minute bending deformation of the arm during pedaling.

Technical Specification Comparison

Product	Accuracy	Measurement Method	Added Weight	Suggested Retail Price
Stages L (single-sided)	±1.5%	Left leg only	+15g	NT$10,000
Stages LR (dual-sided)	±1.5%	Independent left/right	+30g	NT$35,000
4iiii Precision (single-sided)	±1%	Left leg only	+9g	NT$10,000
Shimano FC-R9200-P	±1.5%	Independent left/right	Factory-integrated	NT$45,000

Advantages

• Lightest weight: Single-sided units add only 9–15g
• No impact on pedal choice: Compatible with any pedal system
• Affordable single-sided option: Lowest entry barrier on the market

Disadvantages

• Assumption behind single-sided measurement: Assumes symmetrical left/right power output (doubling the measured side), but in reality most riders have an imbalance ranging from roughly 48/52 to 45/55
• Crank compatibility: Not every crank has a corresponding product
• Temperature compensation: The crank arm is exposed to the elements, so wider temperature swings require more frequent recalibration

3. Spider-Based Power Meters

Representative products: Quarq DZero, SRAM AXS Power Meter, Power2Max NG

Measurement Location and Principle

The strain gauge is mounted on the chainring spider, measuring the torque transmitted between the chainrings and the crank axle. This is the measurement point closest to “total power output.”

Technical Specification Comparison

Product	Accuracy	Compatible Systems	Weight	Suggested Retail Price
Quarq DZero	±1.5%	Multiple cranksets	+60g	NT$28,000
SRAM AXS PM Spider	±1.5%	SRAM AXS only	Integrated	Bundled
Power2Max NG Eco	±2%	Shimano/SRAM	+55g	NT$15,000
Power2Max NG	±1%	Multiple specs	+55g	NT$25,000

Advantages

• Ideal measurement location: Closest to actual output, least susceptible to external interference
• No impact on pedals or cranks: Freely choose any pedal system
• Excellent stability: Located on the inner side of the frame, less affected by temperature fluctuations

Disadvantages

• Cannot distinguish left/right power: Measures total torque only, with no independent left/right display
• Complex installation: Requires removing the crankset, sometimes with specialized tools
• Spec-locked: Different BCDs (bolt circle diameters) require different products

4. Hub-Based Power Meters

Representative products: PowerTap G3 (discontinued)

Measurement Location and Principle

The strain gauge is mounted inside the rear hub’s freehub body, measuring the actual torque transmitted to the rear wheel.

Advantages

• Most realistic power output: Measures the force actually delivered to the rear wheel
• No impact on front-end components: Pedals, cranks, and spider are entirely free to choose

Disadvantages

• Drivetrain loss: Friction losses of roughly 2–4% from the chain and cassette are not accounted for
• Wheelset-locked: Swapping wheelsets means losing power measurement entirely
• Declining market presence: Almost no new products are being released

Accuracy vs. Consistency Analysis

For training purposes, consistency matters more than absolute accuracy. Here’s how each type ranks:

1. Spider-based: Least affected by environmental factors, best consistency
2. Pedal-based: Significant technological improvements in recent years have brought it close to spider-based levels
3. Crank arm-based (dual-sided): Independent left/right measurement compensates for accuracy shortfalls
4. Crank arm-based (single-sided): Left/right asymmetry introduces systematic error
5. Hub-based: Good consistency, but drivetrain loss is a fixed source of deviation

Purchase Decision Tree

Limited budget (< NT$15,000): A single-sided crank arm meter (4iiii or Stages) is the best value

Seeking accuracy and convenience (NT$25,000–35,000): A dual-sided pedal meter (Favero Assioma DUO) offers the best value for money

SRAM system users: Going straight for the AXS Power Meter Spider offers the best integration

Multi-bike use: Pedal-based is the only sensible choice

Top-tier requirements: Shimano’s OEM power crank or a high-end spider-based unit

Conclusion

There’s no absolute right or wrong choice when it comes to power meters—it all comes down to your budget, existing component system, and use case. For most riders in Taiwan, a dual-sided pedal-based power meter strikes the best balance between accuracy, convenience, and price, making it the top recommendation for those just getting started.

Further Reading

• Power Meter Buying Guide: A Comprehensive Comparison of Pedal, Crank, and Hub Types
• Power Meter Buying Guide: Evaluating Pedal, Crank, and Hub Solutions
• The Ultimate 2025 Power Meter Buying Guide: Pedal, Crank, or Hub?
• In-Depth Analysis of Bicycle Power Meter Pedals: Garmin Rally vs. Favero Assioma vs. Wahoo Speedplay