The B Works: Power Meter Indoor and Outdoor Review
06.03.25 08:10 12025-03-06T08:10:00+01:00Text: Der Baranski (translated by AI)Photos: Erwin Haiden, Der Baranski, fotorika.de, Gottfried Gärtner (KOTL)Reloaded: Power meter watt comparison of SRM, Shimano, SRAM, and Garmin. Including tips and tricks for optimal use.06.03.25 08:10 812025-03-06T08:10:00+01:00The B Works: Power Meter Indoor and Outdoor Review
06.03.25 08:10 812025-03-06T08:10:00+01:00 Der Baranski (translated by AI) Erwin Haiden, Der Baranski, fotorika.de, Gottfried Gärtner (KOTL)Reloaded: Power meter watt comparison of SRM, Shimano, SRAM, and Garmin. Including tips and tricks for optimal use.06.03.25 08:10 812025-03-06T08:10:00+01:00
Power meters have finally become widely available on the market and in the cycling scene. Even our Baranski has been using them for almost 20 years and has tirelessly talked himself hoarse, insisting that a power meter offers significantly more benefits than a pair of carbon wheels or a fancy frame kit that supposedly saves nine watts compared to its predecessor. Yet, at the next meeting, the interested expert would show up again with new deep-profile wheels because they simply offered more bling-bling than a discreet measuring unit hidden in the crank spider.
As with everything that measures, the value of a power meter stands or falls with its measurement accuracy. Manufacturers today typically state an accuracy of +/- 1 percent, which of course sounds impressive.
But Baranski knows: This specification only means that the device operates within this margin, so your 300 watts on Friday are exactly the same 300 watts on Sunday—or 297 or 303.
What has always particularly interested him, however, is how accurately these values align with a defined baseline. Especially in competitions, impressive watt numbers are often displayed; however, their actual accuracy remains questionable. This is an entirely different topic that is not so easy to prove.
Indoor power meter comparison test in triathlon Special No. 37 in spring 2022
Therefore, Baranski conducted a comparative test in the magazine *triathlon Special* No. 37 in spring 2022. In this test, a power meter was compared on a Cyclus2 ergometer with the value of the ergometer's brake. The results showed a completely different picture – the variation was immense.
During the test phase, he already cursed himself, as the procedure consisted of an endless power pyramid up to 350 watts and back down again. Anyone who knows Baranski knows: He hates doing such things indoors in a stationary position like the plague.
It became even more thankless when those in the lower rankings claimed that this couldn't be, that Baranski had manipulated the test in favor of the top rankings, that different calculations had been used, and questioned whether it was even necessary to publish the results so explicitly.
Yes, it was. The 350 defined "base watts" of the Cyclus2 were sometimes displayed as 370 or more. If you want to read the test, see here (please start getting used to it: digital paid content).
Outdoor practical review
In the next step, Baranski wanted to know how it feels outside, or rather, how pedal-based systems like Garmin's Rally pedals compare to an SRM or other crank-based systems. He explored this even more complex topic independently at a later point in time.
And this is how he did it: He ran different systems in parallel on the road bike and time trial bike. Of course, this was always done with one system in the pedals and one in the crank or chainring at the same time.
For this, he mounted two Garmin Edge 530 computers on the cockpit, both set with the same configurations, such as the recording interval of one second, and ensuring that phases without speed were excluded. Meticulous attention was paid to setting the zero offset before each ride - more on that below.
Additionally, it had to be ensured that each computer was only paired with one specific power meter. Baranski had already experienced cases where, for example, Garmin/Tacx devices "pushed ahead" even though another third-party device was supposed to be measured manually.
A small tip: On that day, remove all other power meters from the bike computer's settings!
Thankfully, Baranski also had support from Louis Kitzki, who collected data in the higher watt ranges for a week.
For the analysis, the software from DC Rainmaker was used, which is specifically programmed to overlay two or more such files to identify discrepancies.
DC Rainmaker uses it for all sorts of metrics, but Baranski was - as so often - only interested in the hard watts.
And that was interesting again because massive and sometimes not always logical discrepancies appeared.
Sometimes the watts in the intervals were almost identical, while during the coasting phase or break, differences suddenly emerged. Then again, the intervals differed significantly, but during the breaks, the values aligned. And sometimes the entire training ride was all over the place.
The following power meters were tested:
- Sram Red
- Shimano Dura Ace FC-R9200-P (two devices)
- Garmin Rally SPD-SL
- SRM Origin 9 (two devices)
Representatively, a few selected intervals along with deviation
Comparability of the data
Ten to twenty watts of deviation between devices is possible. For those tracking their data over the course of a season, this can make a world of difference. How should one deal with these deviations?
Situation: "Hobby": If you only have one bike with a power meter, it’s quite simple: don’t worry about it. You just assume that the 300 watts from Friday are the same as those on Sunday and, ideally, the same indoors on the trainer as outdoors in cold, wet weather – and everything is fine. Of course, this assumes you trust the one percent deviation claimed by the manufacturer.
Situation: "Professional": Things get more complicated with luxury problems like this: Baranski has several bikes in use, all with different power meters. When he’s doing intervals during the week on a road bike, the current time trial bike, and then on the gravel bike over the weekend, he wants to know how each device measures and where the deviations might come from – apart from his daily form.
Situation: "Nerd": It gets even more complicated with the ever-present drop from the road bike to the time trial position. In this case, being down in the aero bars can easily result in another 3-5% deviation downwards compared to the road handlebars.
Tips for all situations:
#1 Always manually set the power meter’s zero offset before a ride, fully unclipping from the pedals. Note: even if an Edge or another bike computer prompts you to "calibrate," this is not calibration in the conventional sense (this is usually done by the manufacturer). Instead, it’s a zero-offset calibration (offset correction).
#2 It’s also helpful to log the bike or mounted power meter in your training records to enable comparability between different training sessions later on.
Baranski's conclusion on power measurement
- Any device is better than none at all.
- Single-sided measurement systems usually only capture half and double the value accordingly.
- If most high-quality devices cost four figures, there is probably a reason for that.
- Devices for 300 euros are nice, but we would be cautious - both in terms of accuracy and durability. For example, Baranski owns SRMs that are older than his son and still work (the young man is now 18 years old).
- Until a few years ago, we would have always opted for spider-based measurement, but now there are also good pedal-based systems.
- Baranski would be cautious with models where the measuring technology is retrofitted onto crank arms - thus being more exposed to wind and weather than other systems.
Happy testing!
... wishes Baranski - and Bikeboard agrees.
