AeroPod, PowerPod and Newton

Hi all,

Can anybody please confirm or refute my understanding of tilt correction? When a Gen III unit does a tilt correction after the first 5 minutes of a ride, does it take the tilt value used during calibration and use it as a baseline? If it's going through this process no matter what I do, am I correct in thinking that doing a tilt calibration before a ride is a waste of time? It doesn't sound right to me, but just want to make sure.

The second thing I was curious about was the order of the calibration process. According to the manuals, first the calibration ride, then the CDs. How important is this and why? Logically I can't think of any reason why it can't be reversed, but I don't want to draw any conclusions without knowing how the system works. Can someone explain this to me?

Thanks

I'm not sure about the auto tilt but I check mine once a week because it can get a little out of wack but the answer to your 2nd question is on this link http://www.ibikeforum.com/viewtopic.php ... 1078#p5826 and read numbers 7 through a 11 in the operation section.

The auto tilt works the same way the tilt correction works in the iBike 3 software. It compares the barometric elevation profile to the tilt, if it sees it differing over time, it'll correct it. We use a 5 minute range because of how slow barometric pressure updates, and how fast the accelerometer data does.

For the calibration, the reason why we now do the out and back ride before the coastdowns is to establish a riding tilt. Now that we can enter a fixed crr to get more reliable cda numbers, you have to know the riding tilt before doing coastdowns so that you can back calculate a friction number from the set crr number.

It may seem a bit confusing, but we know what we're doing to make this work and that's why we have the instructions set to do in a specific order.

I usually do about one tilt measurement per week, sometimes once every other week. If you are doing a time trial and do a trip reset before the time trial, you will want to do the tilt calibration, otherwise the first five minutes after you do the trip reset will be off. If you are just riding from the house and the first five minutes of your ride are really easy as you warm up, then the tilt calibration isn't that big of a deal.

jparker,
Thanks for the link. That's exactly what I needed.

coachboyd,
Then I take it to mean that when tilt calibration is done before a ride, there is no correction made by the iBike after the 5 min time lapse (or maybe there is, but it doesn't matter because the corrected value will be the same as the one obtained through calibration). Is this true?

Thanks.

Correct,

Let's say for example in your perfectly level garage, your tilt was off and you were showing +10degrees of tilt. For the first five minutes of the ride your watts will be extremely high and your slope line will read at +10degrees from what it should be.

After five minutes, the iBike will look at the slope line, realize it's not matching the barometric pressure elevation line, and correct the slope line. This is the same thing the software does, but the software has the advantage of being able to look at data after the fact, so it doesn't have to have that 5 minute buffer.

If you do the tilt calibration before your ride, then your perfectly level garage will show 0.0 degrees of tilt and you pre and post processed numbers in the software will be the same. FWIW, I usually do about one tilt calibration per week.

If you do a tilt correction before a ride, I still think that the iBike would make corrections if that tilt correction had some error in it - albeit it would probably be quite small relative the the 10 degrees coach boyd was using as an illustration.

Tom