Questionable readings

[Diverdave]

Hi,

I just received my IPro and did a ride yesterday into a pretty strong headwind (>20km/hr). Both the local weather network, leaves and waves confirmed that there was indeed a headwind. The iBike was reading a tailwind for most of the ride and I ended up with average power readings of 68 watts. When I cupped my hand in front of the wind port the wind speed would drop to 0. I also tried performing a wind cal during the ride but it did not change things. I have attached my ride file in case anyone knows what could be causing this.

I should note that relatively the same perceived excertion, I was putting out much higher power numbers at the start of the ride. I have also seen this on a previous ride where I was outputting around 800 watts for the first 10 minutes and then the power dropped off to around 100 watts and remained in that range for the rest of the ride.

What typical wattages should I expect to produce to ride at 30km/hr with no wind to give me an idea what numbers I should expect.

Thanks for any input.

Dave

[rruff]

I just received my IPro and did a ride yesterday into a pretty strong headwind (>20km/hr). Both the local weather network, leaves and waves confirmed that there was indeed a headwind. The iBike was reading a tailwind for most of the ride and I ended up with average power readings of 68 watts.

The item you want is called "wind scaling". Ride back and forth someplace where the wind is light and consistent and is free of traffic. In the software, go to the "analyze wind" screen and note your avg bike speed and avg wind speed. You want them very close to zero... though they should be a little greater than zero if you have cross winds. Adjust the wind scaling by the square of the ratios of these two numbers.

Or, just do your cal over.

[lorduintah]

Wind cal has to be done while the bike is not moving. I am pretty sure there is now a flag that will not allow you to muck with the cal wind if you are in motion riding.

rruf means (average Bike Speed)/(average wind speed) - square this ratio ----- then multiply that value times the current wind scaling in the edit profile. Hold CdA and vary Aero when you enter a new WS value in the panel. This needs to be a route that is pretty much out in one direction then back the same route.

(16/12) = 1.3333 or multiply WS by 1.3333 x 1.3333 to get a new WS.


Tom

[Diverdave]

Hi Tom,

My wind cals were done when I was stopped with my hand cupped over the wind port. I re-did a cal ride and 8 coast downs.

My numbers seem to be mostly in the expected range but with perhaps a little too much variability:

Aero 0.878 (0.46-1.1) - is this variability in numbers acceptable?
Fric 8.484 (6.33-9.86)
CdA .285
WS 3.082
Crr 0.0107
Tilt -0.0%

I will only have a chance to ride tomorrow and will check to see that the wind and power numbers seem more consistent.

I am a little concerned with the variability in the Aero numbers as I was always riding in the drops so a change a greater than 2-fold seems quite high.

Thanks,

Dave

[rruff]

Your Crr looks high and your CdA low. And the high variability is not a good sign. For starters you might want to consider setting these to the defaults for your weight and setup (CdA ~.35?, Crr ~.006?), and then check/adjust your wind scaling via the method described above.

[coachboyd]

For the most part the values you had looked good, but like rruff suggested it looks like your crr was a bit high and cda a bit low.

I have created a profile for you based on that and it's posted here. Save this profile to your computer then open the iBike software. Go to profiles->edit profile->import and then select this file. Hit upload profile to iBike and then you should be good to go from here on.