Low power?

[ScottChapman]

I did a time trial last night, and got my personal best. But when I look at the iBike data it seems a bit off to me. Specifically the power seems to be lower than I would expect.

Anyone care to take a gander at it and see what might be off?

[racerfern]

Nice effort, but now you have the opposite of your posting, Was there a tailwind the entire way? This doesn't appear to be an out/back either. It appears you might be having issues with zeroing out your wind at the start of a ride. Temperature is steady so that's not affecting things.

Give me a good description of the conditions and I'll try to come up with better results.

[ScottChapman]

Thanks Fernando.

The TT route was a "n" shapped; basically three legs.

There was wind, but certainly not a constant tail wind. I did get a good wind calibration before I started the ride.

[ScottChapman]

I may have been confusing you with the other thread trying to understand what the software does to analyse the ride. I think you did really well helping me understand that on behalf of a fellow iBiker.

But the other info I have been providing actually pertains to my own profile which generated this ride file.

I do have reason to believe that the unit is OK (John had validated one of the ones I have, and my results have been pretty consistent).

That said, my wind scaling seems high, and my power seems low.

[racerfern]

So looking at this ride, I come up with about 264 avg. once I raise the wind. Of course as I play with the wind, the wattage goes up or down. Regardless, based on your course description there's no way you had tailwind the entire event. So somewhere around 250w but again without "knowing" the wind there's not much that can be done.

Since you're on a road bike did you do most of this TT in the drops yet maybe did your calride in a more normal "hoods" position? If so, that would account for the lack of wind. It's a possibility.

[ScottChapman]

Good point. I did most of the TT in the drops, and cal ride was on the hoods.

Still, I was expecting to be closer to 300W

[Velocomp]

In the drops position your CdA is closer to 0.34.

You're correct that you show a net tail wind for this ride. Assuming you had no net tail wind for this ride the ride file can be corrected for both conditions.

The corrected ride file is attached; your effort was 317W; excellent!

[ScottChapman]

That feels more like what I endured. Thanks John.

So, I did get a good wind cal just before the ride. Anything other than the CdA I would need to tweak next time?

[racerfern]

Take a look at the difference in the wind. There is a significant difference between the before and after wind analysis. John nailed your CdA and corrected the wind. You still need to look at what caused the wind discrepancy as you now know about the CdA difference between hoods and drops.

[ScottChapman]

John was pretty close. I checked a fellow iBiker at the race and their unit measured a -0.5 ground wind, John corrected mine to -0.3

Anyway, I think I cna retire now...

Thanks guys!