In this article we explain why spider-based powermeters are more accurate than any other kind of powermeters.
Table Of Contents
Accuracy of powermeters in General
A power meter is designed to measure the power you generate to move you and your bike forward. Most power meters measure the force generated in the form of torque and the cadence and calculate the power in watts. Spider-based power meters, such as power2max, measure the power transmitted from both legs via pedals and crank arms to the chainring in one sensor. This is what we call “complete dual-side measurement.”
Only the power of both legs is meaningful for targeted training. Even with almost “equally strong” legs, a one-sided measurement can lead to greater deviations. With each turn of the crank, the power distribution of the legs fluctuates and fatigue, as well as different intensities during intervals, can lead to an uneven distribution.
Two sensors for measurement
Measuring both legs separately using pedals or crank arm-based powermeters is legitimate and already more accurate than one-sided measurement. However, two sensors mean two potential sources of error. Even if both sensors have an accuracy of +/- 1% according to the manufacturer, this means that they can potentially deviate from each other.
This refers to movements that do not serve propulsion. For example, when you ride out of saddle, the crank arms or pedal axle “deform”. This deformation is measured by the powermeter, but cannot be distinguished from the deformation that is responsible for propulsion. With spider-based powermeters, this deformation also takes place, but has no influence on the measurement result.