Page 1 of 1

Good feedback on PP accuracy - constant uphill test

Posted: Fri Jul 15, 2016 12:21 am
by Bugsbunny
I've now owned the PP for about 3 months and done over 1000km and wanted to share some good feedback to John and the community.

John kindly helped me calibrate my PP and since then I've been trying to "test" it out as best I can. I don't own any other powermeter.

I recently road a Strava segment that was all uphill - took me about 12min and average gradient about 10%. No wind and no drafting - not that it mattered as my speed. I rode it as best i could, some times seated and sometimes out of the saddle to get through the sharper pitches.

But what was interesting was that I rode with another guy, same weight as me +/- a kg, and very similar bike weight and setup as me. We crossed the line about 2 seconds apart - him first. He was using Garmin Vectors.

The average power readings for him and me were 194 / 193 watts respectively.

Whilst getting a total ride power average is not as important as say more the instantaneous power, I am still very happy with this result. For rides with little varying power such as this one, it is showing accuracy I think at very very high levels. Awesome product!

Re: Good feedback on PP accuracy - constant uphill test

Posted: Fri Jul 15, 2016 12:00 pm
by Velocomp
Sounds like his Garmin pedals were well-calibrated :-)

Re: Good feedback on PP accuracy - constant uphill test

Posted: Sat Jul 16, 2016 1:25 pm
by hydraliskraider
Generally, the steeper the slope, the easier it is to estimate power directly from opposing forces - this was how I used to measure power before I picked up a DFPM, along with Gribble's power calculator.
For most of us, a slope of 10% on a fairly calm day is nearly 100% down to resistance from gravity, rolling resistance, and drivetrain loss.
This is one of the reasons that hill repeats used to be such a common training tool - before power was commonplace, it was a great way to consistently measure gains in power/weight ratio intervals and get an idea of overall power as well.

Re: Good feedback on PP accuracy - constant uphill test

Posted: Sat Jul 16, 2016 7:25 pm
by Velocomp
hydraliskraider wrote:Generally, the steeper the slope, the easier it is to estimate power directly from opposing forces - this was how I used to measure power before I picked up a DFPM, along with Gribble's power calculator.
For most of us, a slope of 10% on a fairly calm day is nearly 100% down to resistance from gravity, rolling resistance, and drivetrain loss.
This is one of the reasons that hill repeats used to be such a common training tool - before power was commonplace, it was a great way to consistently measure gains in power/weight ratio intervals and get an idea of overall power as well.
Using the Advanced Stats feature of Isaac you can see the various power components due to gravity, aero, and friction. On a steep uphill the slow speeds reduce the aero and frictional components of power to very small numbers.