Big difference when route analysed

[gerrard]

Went on a solo 3.5h ride today - aiming for fairly steady intensity. Route had one very long climb but at a minor gradient.

I was tired and it felt hard to produce watts when watching the ibike. I came home, downloaded the ride, analysed route, and got what I think is a substantially different result. NP went from 178w to 202w. And other associated metrics changed too.

When I did the "analyse route" it detected 7.5% drafting when there was none. I often get 2% ish detected but this is quite a difference considering it was a relatively calm day. It did start to rain from about the 2/3rd point. Would this have affected the numbers to such a degree? How would I know?

I've been using the ibike for a few months now and am really valuing what I learn from it, but constant unknown things like this make it really hard for me to have confidence when I'm out there using it. In this case I was using IF to try and understand my Ironman pacing, but being out by such a big number makes it of no use at all!

Any help appreciated.

Thanks
Gerrard

Ride file attached

[racerfern]

I shy away from having the software do an analysis mainly because I'm careful about starting out with a good wind cal, temp adjustment and tilt. IMO the route analysis is awesome for salvaging a ride that has any kind of issues but for the most part I keep everything unchecked except for entering the known elevation. I always enter my starting and ending elevation.

With that process, your before and after numbers are nearly identical although I think your wind is low for what is somewhat an out/back ride.

If you change the smoothing to about 20 minutes you see a steady state effort for both power and heartrate. This consistency even includes the rain portion, so it doesn't appear the unit was affected by the rain.

If I were you I would double check your wind scaling, but that's it.

[gerrard]

From your comment "Absolutely, you're always better off running it through the software first. You have to use the software to download it anyways so just save what you downloaded and your done. This would be the minimum." in this thread http://www.ibikeforum.com/viewtopic.php?f=6&t=1942 I thought it was best to analyse route on every ride.

I did a new calibration ride just last week (and only been on the trainer since) in really good conditions (very hard to get a calm day round here) and ended up with windscaling of 0.887. This is below the range given in this thread http://www.ibikeforum.com/viewtopic.php?f=6&t=1550 for handlebar mount. Would this be a likely cause?

BTW Velocomp - there is so much information (some old and some new) scattered through these forums. Any chance of getting one authoritative source like a set of articles /modules / wiki or something? I really want to understand how to use my ibike properly / to it's full potential, but currently can only do that though the good wil of Fernando and a few others as they have time. Having all the authoritative, current, and relevant information in one place would help a huge amount.

Gerrard

[racerfern]

Agreed, your wind scaling is to the low side for a handlebar mount. IIWY I would try another cal ride.

Yes, you have to run it through the software anyways. The one thing that gets corrected through my procedure is any tilt variance due to elevation skewing because of barometric pressure swings. This was practically nil in your particular ride. That simply means the barometric pressure was consistent throughout the ride but there are time you can see significant swings in starting and elevation even if you're starting and ending in the same place.

[gerrard]

Will do - thanks

[gerrard]

Well I just did new cal ride in absolutely perfect conditions today and it only had very minor impact on wind scaling in my profile (changed it from 0.887 to 0.880)

The good thing about the ride was given dead calm conditions (and I mean not a breath) I can finally see how wind works / affects power readings. Looking at the file there is a minor difference in windspeed to wheel speed (above and below) all the way but this was generally only up to 2kph.

The latter part of my ride was on a busy road with a lot of traffic coming past me. In that case it was showing I had a tail wind of anywhere from 5 - 15kph which I guess is just the disturbance of all those vehicles going past - not something I would think about or be aware of normally but clearly does help the speed along!

Interestingly when I opened the file in iBike software it still detected 7.4% drafting so I'm guessing that's related to this traffic disburbance. If I analyse route with this then it bumps up my avg / norm power by 20watts. All of my rides involve busy routes at some stage so I assume doing the analyse route will actually misrepresent my data so just won't do the analyse route from now on. At least that way the numbers I see when I'm riding will be consistent with what I look at afterwards in the software.

I feel like I'm finally starting to come to grips with how this thing works. I now have confidence in the cal ride I've done and have a known benchmark to work from. Thanks for all your help and patience through this Fernando.

[racerfern]

First of all, you're welcome. You are certainly coming to grips with it. FWIW, I also ride on busy roads that tends to skew the wind. For me it's usually from a 45-75 angle headwind from the left side. So what that means as the cars whiz by they create a huge break in the wind and I definitely feel the effects and benefit. However, when I turn around I don't see as much of a tailwind because now the cars are not between me and the wind. Huge difference in wind effect.

I'm confident my scaling and setup is correct so the only thing I ever check in Analyze route is Enter Starting and Ending Elevation, nothing else. If for some reason your ride is messed up because you didn't zero wind or whatever then checking boxes goes a long way toward saving a ride.

Have fun.

[still-chasing]

I use my ipro for commuting and here's my routine. Before each ride, I leave the bike/unit outside for at least 5 minutes to acclimate. Before leaving, I do cal Cal wind and check altitude and adjust if necessary. Most of the time, the altitude is off so I set it the correct value. I do Cal wind along the route when possible like stopped on a light. I do this routine all the way to my destination and after downloading the file, I see that the altitude is still off especially at the end of the ride. I have my software Preference set to "auto fine tune downloaded file" and also "automatically analyze route". Checking The "tilt plot" graph, The lines after doesn't seem to mesh.

Here is an example of the 2 x 20 interval I did today.

Please advise on what to do.

BTW. Just downloaded the new software update.