Test: The power meter has honestly earned its name as the most important training control tool in recent years. Not only in the professional business, but also for amateurs and ambitious hobby cyclists, the power meter is a must. If you're lucky or shell out enough for your dream bike, you'll often get the model variant delivered directly with a power meter. However, a power meter is not just a power meter here and the approach to the topic of watt measurement can be completely different. We were able to test the in-house Shimano power meter installed inconspicuously in the latest Dura-Ace crank.
Power meter is not equal to power meter!
The approach to power meters is and has been completely different from manufacturer to manufacturer in recent years. The most logical approach, which has largely prevailed to this day, is measurement using strain gauges in the crank area. A first approach is the measurement in the crank star itself, here the torque is recorded and offset against the angular velocity, which results from the cadence. Other power meters measure in the hub on the rear wheel, in the pedal, in the bottom bracket axle or in the crank arm. With the different systems, of course, there are also different characteristics of the measurement. Cheaper variants sometimes only measure the performance of one leg. The values are doubled to arrive at the overall performance. Here, of course, one quickly faces the problem of inaccuracy, since both legs are not always equally strong or generate the force with a time lag. To avoid this problem, Shimano uses a real left/right measurement in its Dura-Ace power meter and has installed strain gauges in both crank arms to enable an exact measurement of the power of both legs. The big advantage here is that, compared to the otherwise very precise measurements using a crank star, the balance is often calculated using the cadence. However, the Shimano power meter delivers significantly more accurate results here due to its structure.
Shimano Dura-Ace power meter review
Let's go into a bit more detail with our Shimano Dura-Ace power meter. The crank actually looks the same as all other Shimano Dura-Ace cranks, with the big difference that it can measure power. Well, if you take a closer look, apart from the price (1.149 euros), you will see that something is different. Because there is a small cover on the chainring side. A small LED is attached here and the connection for charging appears under the cover. The permanently installed lithium-ion battery, which should last around 300 hours when fully charged, can be connected using the supplied magnetic charging cable. There are also differences to the classic Dura-Ace crank on the inside of the left crank arm, because the built-in strain gauges are visible here. Last but not least, you also need a pickup in the form of a small magnet, which serves as a counterpart for the cadence sensor on the frame. So much for the optical subtleties, also from the technical side the differences apart from the power measurement are only very small, because in our case the Shimano Dura-Ace power meter weighs 53 grams with 39/175 teeth and a crank length of 716mm, what just 70 grams more than the counterpart without a power meter. Weight should no longer be an excuse. As you can already imagine, the power meter is equipped with Bluetooth and ANT+ and is compatible with any bike computer.
The Shimano Dura-Ace power meter also scores points when it comes to reliability, because we didn't have a single disconnection during our test period of almost 6 months and always received reliable and meaningful data. It is only important to note that the crank always has the latest firmware via the Shimano E-Tube app and that a proper zero point calibration is carried out regularly. This is easily done by unclipping the bike and placing it on a level surface before setting off and aligning the crank arm on the drive side vertically to the ground. Now you can calibrate via Bluetooth using the app, with ANT+ using the bike computer or directly on the device itself by pressing the button on the charging port.
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FTP test with the Shimano Dura-Ace power meter
Of course, for such a test, you should also have it clarified that you are really fit and fit for action. Then the classic FTP test can be used to determine the performance zones. Here, after a 30-minute warm-up, 20 minutes are tackled with maximum (even) performance. That doesn't mean sprinting straight away, but setting a high pace, which you can keep going for 20 minutes, similar to a time trial. A steady 20-minute climb, a flat stretch or the home trainer are suitable for this. After 20 minutes of torture you get an average wattage. This value is then multiplied by 0,95 and you get your FTP. The FTP is the Functional Threshold Power, which indicates the value that can be held for approximately one hour. With the help of specialist literature, you can now derive various training zones for intervals and basic units and thus start your training with the power meter.
Useful training intervals with a power meter
Anaerobic Endurance: 5 x 3 minute intervals at 105-129% FTP, with 3 minute recoveries each.
Muscular Endurance: 5 to 12 minute intervals at 91-105% of FTP, with at least 2 to 4 minutes regenerative in between. In total, the intervals should add up to 20 to 30 minutes.
Sprint power: 6 to 15 seconds at maximum power with 3 minutes of rest each time. The whole thing is run until the average value of an interval is 10% less than the highest average value of the entire interval series. Example: In the 2nd interval, 10 watts are reached over 1000 seconds, in the 5th interval only 900 watts and in the 6th interval only 870 watts. Here the interval training should be ended after the 6th.