High power readings for first few minutes of riding

[turbomentor]

I noticed recently that my iAero GIII shows some off the scale high power readings for the first few mins of the ride before settling in to "normal" readings. It's not a huge deal because it always seems to go away before I am done warming up, but just out of curiosity, any idea what causes this and how I can potentially fix it?

[R Mc]

Guess: temperature changes throwing off the elevation for the unit--then the tilt correction kicks in. Run the "analyze power" thing under tools (and in preferences choose the option that lets you see "before" and "after" tilts--odds are that you'll see the elevation (green line) jumping in those first 5 minutes . . .

[turbomentor]

Thanks! I'll check that out.

I try to let the temp equalize but perhaps not equalizing long enough.

[racerfern]

If you are doing a tilt calibration before every ride that would account for it. The GenIII adapts itself to existing conditions. So... assuming nothing crazy happened on your last ride, then do not do another tilt calibration. Just let the temp settle to ambient outdoors, do a wind offset and ride.

I have a spot on the floor that I know is .1%. Before I ride away I put the bike on that spot. As long as I am within a tenth of a degree or two I ride away. If I slammed something, broke something or changed something, then I will redo my tilt. Then for the first 5 minutes I get crazy readings.

Bottom line, check your tilt to see if it is about normal. If so, leave it alone, do not redo the tilt cal because the unit will have to learn the whole process over.

[Velocomp]

Here's what is going on.

In your cal ride both your wind scaling factor and your riding tilt are determined.

Riding tilt is the correction factor that accounts for the effects of your body's weight distribution causing changes to the tilt calibration of your iBike.

A correct riding tilt measurement will give you spot-on readings, even during the first few minutes of each ride. So, if your tilt calibration is correct prior to your cal ride then your riding tilt will be correct and all will be well. However, if there is an error in your tilt cal prior to the calibration ride then your riding tilt will also be "off".

The good news is that an incorrect riding tilt measurement is not a big deal with the Gen III.

Why? If your riding tilt is incorrect the first 5 minutes of your ride may be off, but after that the tilt correction algorithms of the Gen III will kick in and all will be well.

And, if you want "perfect" results for the first 5 minutes you can correct the first 5 minutes of your data with the Analyze Power... function.

[turbomentor]

Thanks John.

So what it sounds like you are saying is that my tilt cal may be off (from my cal ride). Sounds like you are also saying this is not really a big deal because GIII self corrects this. I can fix data later using the Power Analyzer.

Also, I guess, I can do another set of coastdowns and another cal ride; store that profile and see how it performs right?

[coachboyd]

If you want, you can send me your profile to me at boyd (at) totalcyclist dot com and I will take a look at it. I can make a quick change or two and send you back the profile for you to use or I can tell you which numbers to change.

[turbomentor]

Thanks Coach Boyd for the offer.

I thought it was just easier to go out and do another set of coastdowns and a cal ride. I'm a data geek anyway and I enjoy this kind of thing and it's not like it's difficult.

Did 6 coastdowns and a cal ride then dumped that into my laptop, analyzed and came up with a new profile then dumped that back into the iAero and went for a ride. In the two rides I've done since, I have not experienced this issue. I am experiencing an issue with Real Time power data when compared to a PT though...I posted on another thread.

IB3 software is great for post ride analysis but in my case, I am looking for good #s when on the bike as I do a lot of intervals. Any suggestions would be appreciated!

1. I always do a wind offset.
2. iBike temp is usually within 5 degrees of outdoor temp where I live (South FL)
3. I did a very precise tilt cal on my cal ride and never do another tilt cal.
4. What am I missing here?

Thanks Coach!

[turbomentor]

I noticed recently that my iAero GIII shows some off the scale high power readings for the first few mins of the ride before settling in to "normal" readings. It's not a huge deal because it always seems to go away before I am done warming up, but just out of curiosity, any idea what causes this and how I can potentially fix it?

I am still having this issue but think I have deduced the reason for it.

I did my coast downs/cal ride in the drops which is where I spend the majority of my riding time.
I usually always do my warmup on the hoods.
Riding on the hoods vice the drops should definitely affect the tilt the IAero is seeing since my CG is further back than it would be if I was in the drops.

I am surmising this is one reason I continue to see poor numbers in the beginning part of the ride!

[cjonbike]

A question, I read somewhere on the forum that the Gen3 takes about 3-5 minutes into the ride to find its sweet spot. Is this true? If this is the case maybe this has a bit to do with the off numbers at the beginning.

Just a thought

Chris

[coachboyd]

Yeah, the tilt correction will happen after the first five minutes of riding. If you are on the hoods, your riding tilt will be a lot lower (more negative) than riding in the drops. I have even seen people who ride in the drops who have a positive riding tilt.

But this could be the reason why you see the off numbers at the start of the ride. Still, it shouldn't be more than a few tenths of a degree of slope. If it's closer to one percent or more, then something else is going on. This is where you might want to check the tilt when you are starting off your ride. I usually give mine a check a couple times a week just to make sure everything is in check.

[gregh3285]

I saw the same thing on my Gen III iPro. My altitude is about 760 ft. When I initially started my ride, it was at 250 feet and, within the first 30 seconds, reestablished itself to 740. The outside temp 37 F. Inside it was 67 F. I thought I left the iPro outside long enough. I guess not. Just doing an analyze power wasn't enough to get data that made sense, though. I went in and made some hand-edits of the altitude data (not for the faint of heart, save a backup, etc.). Along with running Tools -> Analyze Power..., that worked.