"Bad Calc" after every calibration ride on IAero GenIII

[robaroy62]

I've followed the procedures for calibrating the iaero by first doing 5 coastdowns followed immediately by a calibration ride, but after 6 tries I'm always receiving "bad calc." I check the tilt and the wind offset each time before beginning the entire process of coast downs followed by the calibration ride. I haven't had to recalibrate tilt since calibrating it the first time. It always zeros in perfectly. The wind offset doesn't seem to be a problem either. Of course, I'm very careful to keep my same riding position for the coastdowns and calibration ride.

The course has little traffic, no stops (except when turning around), is flat with steady wind in one direction, but not gusty or stronger than 10 - 15 mph. I start from a stop. When I do my turn around I wait for "go back," then do a 180 and press the center button. I never quite finish where I started, (usually I'm within about 20 - 50 feet past where I started.) Am I missing something else I should be doing? I upgraded from a GEN II and LOVED IT!

[coachboyd]

Hey there,

sorry you are having some problems getting your calibration ride. We'll get you taken care of. Were you able to save the calibration ride as an ibcd4m file? If you did it will be located in the iBike folder under calibration rides. Look for the one that has the date of your ride on it. If you can do me a favor and send that file to me at boyd (at) totalcyclist dot com I will take a look at it for you and hopefully be able to help you. If you need help finding that file, you can also use that email address. Talk to you soon.

[MdC]

I had a similar problem and it turned out the tilt meter was the problem. I noticed when riding around that the tilt being reported was about 3.5% over what I was expecting even though I zeroed the tilt meter. Perhaps you could test the tilt?
Velocomp sorted me out with a replacement.
Good luck

[gregh3285]

I had a "bad calc" 4-mile ride. I did a second one it was fine. For the first one, my iBike was in trainer mode. When I got home, I was able to extract the data of the "bad calc" ride. It seemed fine within iBike 3. I'm treating my first iPro cal rides as throwaway once we get a day here in Northeast Wisconsin that's a little less windy. The wind was at about 15 mph the day I did the coast downs and 4-mile ride. Yeah, I know, that's not idea. But, the way I figure, some data is better than no data. What does "bad calc" mean?

[coachboyd]

A bad calc can happen for a couple reasons. If the wind scaling is too high that will give a bad calc message. This is usually because of the wind offset not being done before the calibration ride, or in a VERY few circumstances it could be the wind sensor is bad. Also, if the riding tilt is too far negative (like a -3.0 or more), this can return a negative rolling resistance. This is solved by doing a proper tilt calibration before the calibration ride.

If it's a very windy day what can happen is the wind will gust and swirl and not be consistent. So if on the way out you have +15 mph of wind, but the way back because of swirling wind you have -10mph of wind, that can lead to a bad wind scaling and will throw off your cda values.

If you get a calm day, do a calibration ride if you think yours is suspect. You don't have to do any coastdowns beforehand, and the cal ride will just store the wind scaling and riding tilt. If you would like to do coastdowns in the future, you don't have to do a cal ride afterwards because wind scaling and riding tilt are still stored.