December 18, 2017 Dustin Porter

Cycling Training: Adjusting the Feedback on Your Power Meter

Have you noticed a delay in your power numbers when you get out of the saddle for a spring or quick burst with your iBike power meter?

I’ve received a few e-mail about this and have investigated the mystery. Here’s the explanation.

If you’re not quite sure what I’m referring to, here’s the scenario: you’re riding along with your power meter at a steady pace. The speed and power numbers appear on your consistently, as always. The road pitches up to a short steep bump and you decide to pop out of the saddle and give it all you’ve got for 10 or 20 seconds. As you look down to amaze yourself with the raw horsepower you’re able to generate, you notice a stagnant power display number. The iBike power meter reading isn’t changing. Then, after about 3 seconds it starts to show higher power readings. Huh? Is there something wrong with the power meter?

The answer is no, there’s nothing wrong with your power meter. It’s operating as it was designed. Here’s how it works. . .

The iBike Newton power meter is an amazingly precise measurement device. It analyzes a ton of information that comprises the power measurement figure we see on our screen. This includes hill slope, wind speed, pedaling efficiency, and a bunch of other things, all at once.

Maybe you don’t realize it but our riding environment is constantly changing. The wind, road surface, and road slope change. Along with environmental forces, our pedaling force is never distributed evenly around the circular stroke. For a sneak peek about pedaling efficiency, check out PowerStroke. It’s pretty incredible! There are dead spots and surges no matter how hard we try to turn perfect circles. As well, our cadence (the speed at which you rotate the pedals) changes constantly. So there are a lot of changes going on as you ride that transfer to your power meter.

As I mentioned above, the iBike Newton power meter is a pretty amazing device. It collects all of the various inputs and takes multiple readings per second. It receives a staggering amount of information. When we think about it, if it displayed power at each instant it would just be a blur of unreadable, unusable numbers.

Instead of presenting a spastic strobe, it displays power over a meaningful period time, providing a comprehensible and useful number. For iBike power meters, the display period can be set to reflect readings from 0 seconds (think raw streaming data), 2, 3, 5, 10, and 30 second intervals. So, if the default is 3 second intervals, when you stomp on the pedals, you are not going to see the effect of that burst until three seconds later, as an average of the power you put out over that three second interval. Regardless of your personal selection, the iBike Newton records the ride file data without any filtering and the highest sensitivity do you can play with the data in Isaac free ride analysis software.

How is this useful? Well, if you race crits, you may want to see more immediately responsive data, so you’d select 0 or 2 second filtering. If however, you’re racing a 40k time trial, you may choose to set your filter at 10 or 30 second intervals to provide smooth readings. At the end of the day, the choice is yours and that’s what makes it so cool.

Thank you for your submitting your questions and blog topic requests. Many of us have the same questions but do not ask. Thank you for letting your voice be heard.

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