AeroPod, PowerPod and Newton

Hi there.
Loving the Power Pod so far.

One issue, I'm having, however - is that I'm not sure if my power output is correct or not.

I calibrated, last week. Then went on a couple of rides. An 8 mile one and a 23ish mile one. My average watts were lower, and my calorie interpretation from that was surprisingly low. Approx 400calories for 23miles, mixed terrain but probably more offroad than on the road.

So - I went and looked at settings, set weight, tyres etc more accurately,and checked the position of the mount. It was pointing about 10 degrees upwards - so made this as horizontal (on handlebars of Mountain bike 27.5inch tyres, front suspension only)
Did a new calibration.
Next ride seemed better- but weirdly seemed to read what seemed fairly accurately for the first half - and then I had prolonged periods (off road, working hard due to terrain, but not fast) where it was suggesting my power output was 50w - certainly the second half (flatter terrain, but more off road) seemed consistently lower.

I checked the pitot tube at the end of the ride, not blocked, even partially.

So.......
My question I guess is........ am I calibrated correctly? (bet you're sick of that question) or am I just not putting out as much power as I hoped. I think my concern is that for my weight, age, speed and distance - my calorie output would be approx 50%+ higher - thus......my puzzlement.

Any thoughts? Thanks in advance.

There are several things going on:

1) You're riding a mountain bike. You are sitting more upright than on a road bike, so your CdA should be higher than 0.35. I adjusted it to 0.39--this raises your overall watts, but not by much. On the flats, where aero forces are the most important, your watts rise by only 2W in the section between mile 11.5 and 12. This is not surprising, because on the flats your bike speed is about 10 mph.

2) On the flats there is very little opposing wind force; the primary resistance is rolling resistance. Your rolling resistance setting of 0.01 is already set for off-road conditions. Just for fun I adjusted it to 0.02--a resistance that would be like riding in soft sand--and your watts increased from 55W to 95W. That is not a huge increase, particularly when compared to the hilly portion of your ride, where you were putting out 170W climbing a hill.

What kind of terrain is your off-road riding? On the flats, at low speeds the primary opposing will be rolling resistance, and that force generally won't be very much unless you're riding in something like soft sand.

Thank you for the Reply John.

The terrain is mixed, probably 30% road, 65% gravel/dryish mud. And maybe 5% softer mud (possibly less than this).

I had tinkered with the CdA a bit myself before messaging here, and it certainly seemed to be one of the relevant differences.

I don't know if it helps, but the first of the larger peaks is on concrete/road and the second of the bigger peaks is on gravel/dryish mud.

By soft sand do you mean compact samd or loose like a beach?

It's more sort.of compacted.mud with loose stones. Reasonable effort required compared to road.

I made a few changes. Changed the CdA to 0.39 and the rolling resistance to 0.019 (might have over done it, but today was muddy, a bit slippery, harder work - but I did also put in more effort, I believe.

I've attached the same ride (minus some of the extra flat bit at the end of the last one.
Not sure if that's helpful for you to look at or not, but it looks more realistic to me......... if maybe slightly too high power........ not sure.

I'm concerned that your Crr rolling resistance is too high; you are traveling at about 10 mph on the flats, and at this low speed the primary source of opposing force is friction.

If you have a heart rate strap it would be great to pair it to your PP. We could compare your HR effort to your power effort.

I'm afraid I don't have a Heart rate strap, but I'm tempted to get one.
I do track it with my garmin, however - not sure if that is of much use to you.....

I've attached HR and Speed (blue line) as well as HR and Power (pink line).

I may have to look at getting a chest strap to pair.

By rolling resistance is too high, do you mean 0.019 should be lower, say at 0.015 or something? Or.......

Just back from another ride.

The flat bit is quite hard work - I was really 0aying attention to the terrain and thinking about it. Much more effort to pedal than on a flat tarmac/road. It's very very bumpy, so lots of power lost there I guess, and in places it's slippery because been raining recently so more muddy. Don't know Iif that helps as well, or not.