lbmxj560 wrote:
That's not strictly true. The 2% refers to the range of accuracy, not how inaccurate the power meter is.You are combining multiple things... measurement inaccuracy is independent of inaccuracy caused by a user's power imbalance. The manufacture's accuracy rating does not take into account inaccuracies that a user might contribute. Here is a quick illustration to show how a 48/52 power imbalance would result in a 4% error that is entirely unrelated to the unit's accuracy range for a simple measurement:
Left Power: 120W (48%)
Right Power: 130W (52%)
Actual Power: 250W
Stages 1-Sided Power: 240W -4% error (2x L Power)
That left power 120W reading also has a ±2% error range, so the user's actual power could be in the range of 118W - 122W.
It does not matter that imbalance may change during the workout. It introduces yet another variance on top of the inherent accuracy of the measurement itself.
If you add it all up, you might be producing 255W, but the unit might read 240W. Or not. The errors are cumulative. In this example, a single-sided unit has an error range something like ±6%. That is why a unit with total power (like crank, pedals, or a hub) are more likely to be closer to reality than a single-sided meter.
chaparral wrote:
Except most people do not have a consistent imbalance. Most people will have a balance that varies with length of ride, power zone, and other variables.