Just in case you’re wondering, the fun level of these rides was dialed right down to zero.
Tire pressure was standardized to 100psi. I set the zero offset on each power meter before each test run. I also made certain that all of the critical settings were the same: Are the differences large enough to significantly affect one’s training? Is this something that the average user – the fat of the bell curve – will care about?īefore beginning any of the tests, I updated the firmware on all of my devices (an exercise of patience in itself).
I proposed – let’s look at these files as if they belonged to one of your customers. From them, I hoped to learn the practical side of things. They analyzed my files using the multi-file analysis capability in their popular WKO+ software. I visited their Boulder, CO office for an afternoon, in hopes of convincing them to crunch some numbers (lucky for me, they kindly agreed). Next, I had help of Gloria, Marcus, Dirk, and Gear at TrainingPeaks. I hoped to learn the very nitty-gritty from him the data-packet-by-data-packet run down of exactly what was happening during my rides. Chung analyzed my files using uber-geek power software, Golden Cheetah. That is good news for us, because he is a master of slicing-and-dicing data. At heart, he’s a stats guy, with a very big cycling habit. Among other feats, he created the Chung Method of Estimating CdA with a Power Meter. If you don’t know who he is… well, you should. First, Berkeley professor and Slowtwitch forum member, Dr. A power meter is only useful to the extent that it is also accurate and repeatable… I simply wanted to learn how the data transmission half of the equation affects this.įor data analysis, I had two wonderful resources. Your 200-watt average power from that last ride could be completely bogus. If you can’t remember the last time you did that (or don’t know what ‘firmware’ is), chances are your data is not as accurate as it could be.
Do you have your Garmin set on 1-second recording or Smart Recording? Are you including zeros? When was the last time you set your zero offset? What is dictating the start and stop of your head unit – GPS movement, wheel speed, or a manual timer? Oh yeah… and there’s that little detail of updating the firmware in both your power meter and head unit. Seasoned users of power meters also know that you have to deal with random data drops and interference.Īlso, on a very basic level, the settings of a head unit can hugely affect the data you get. As we learned in part one of this article, most ANT+ head units randomly pick a single data packet each second (out of four that get sent every second). Shouldn’t all of the power files be identical if all of the receiving devices are reading off of the same power meter? Not necessarily. I tested each power meter by itself, but transmitting to multiple head units. I had four head units to work with: a Garmin 500, Garmin 310XT, CycleOps Joule GPS, and SRM PC7. I tested three power meters – Stages, Powertap SL+, and Dura Ace 7900 SRM – each individually. We wanted to look at various head units, to see if they affect the data you get. Not wanting to dive in too deep right off the bat, the first round of testing was relatively simple. We will also analyze the results and break down what you need to know. We will look at a handful of test runs that I did, explaining the intent and protocol for each. As with the previous article, I’ll keep the discussion centered around the four power meters with which I have experience – Powertap, Quarq, SRM, and Stages. Let me be clear: This article does not declare a ‘winner’. Does it really make a difference whether a power meter is time or event-based? When looking at a power file, can you actually see data differences based on whether your head unit records at half second or one second intervals? Perhaps most importantly – can you train effectively with any power meter? Does a $4,000 power meter work better than a $700 one? There are many questions indeed. If that was Powermeter 101, this is the sophomore-level Powermeter 201.Īfter all of the phone calls, interviews, emails, and questions, I wanted to see how it all fleshed out in the real world. In essence, we covered the complicated topic of how power meters and data transmission actually work. Our first article was a primer, of sorts. If you missed part one, it is located HERE.
This is part two of our technical series on bicycle power meters.