How accurate are Power2max powermeters?

We calibrate our power meters using a custom built torque sensor that has an accuracy of ±0.1%. We achieve, and guarantee, precision of ±2% or better throughout all environmental influences with the NGeco and ±1% with our NG power meters.

Do I need to recalibrate my power2max if I change the crank or chain rings?

Changing cranks or chain rings does not affect calibration. You can also use oval chain rings (e.g., Rotor Q-Rings, Osymetric, etc).

How can I calibrate my Power2max myself?

There are two important values for the precision of crank-based power meters: zero-offset and slope. The zero-offset is the value that the power meter reports when there is no torque, i.e. when you are not pedaling and there is no tension on the chain. The slope indicates how much the measured value changes as torque increases.

power2max power meters automatically update the zero offset when you stop pedaling. Anytime you stop pedaling long enough (approximately 3 seconds or more) power2max updates the zero offset. You can also update the zero offset manually through a compatible head unit.

The slope does not need to be calibrated by the user. Other systems require calibration in two cases:

1. When you change chain rings 2. Due to aging of the materials of the power meter

power2max power meters have been designed in such a way that you can change chain rings without having to recalibrate the unit. Calibration remains unaffected by the choice of chain rings and chain bolt torque. We do however, recommend tightening chain bolts to the prescribed torque.

Furthermore we have constructed power2max power meters in a way that aging of materials is not an issue. You don?t have to worry about the calibration of your power2max.

If you want to verify the calibration of your power meter anyway you can send it in for calibration. However, we don?t see this as necessary.

Another possibility is to conduct a dynamic calibration yourself: you can compare the values from your power2max with a CYCLUS 2 professional ergometer. This ergometer also has a known precision of ±2%. Please contact us for a comparison test protocol if you wish to conduct this test.

The power values on my Power2max seem low compared to other power meters I use. Do I need to send the unit in for calibration?

As the inverse relationship between the cost of power meters and the number of competing manufacturers continues to grow, the accessibility of data is far more available to the average rider. However, with power values varying from one platform to the next, it’s hard to know which power meter’s data to rely on.

While the simple solution is to stay within one brand or, to a higher degree of extremism, rely on the values of one power meter, this isn’t realistic given the different training requirements of athletes. And, though the root function of all power meters is to measure the power output of the rider, it’s important to remember that different power meters arrive at that number in different ways. That is to say that we expect the values to differ to some degree.

At the foundation of the Power2max philosophy is the concept that force vectors vary depending on the situation, in much the same way that the aerodynamics of a wheel vary over the course of a ride. Therefore it is our belief that dynamic calibration is the only true test of accuracy. To that end we’ve created a dynamic calibration device that measures power outputs in ascending and descending value. A procedure that is done with every Power2max power meter sold. We do appreciate your concern and are happy to escalate our investigation into your power meter’s accuracy if needed. However, to minimize the amount of time you are, or might be, without a power meter we’ve developed a test that you can do to determine if your power meter’s power values are outside where we would expect them to be.

Here’s what you’ll need:

  • The weight of you and your bike (in kg)
  • A hill at least 1.5km long and 5-6% in grade
  • The actual length of the hill
  • The height difference (altitude gain)
  • And total time

Once you’ve conducted that test 3 times and collected that information visit this site.

Insert the values where indicated and press “Calculate Power”

The “total power (due to 98% efficiency)” should give you a value that is +/- 10 watts from the value given by your Power2max power meter. If it is, breathe easy, all is well. If not, you’ll need to contact us further as we’ll need to send the unit to Germany for further testing.