Auto tilt cal after 5 min.

[GWPOS]

I know it is useful to have the tilt automatically adjust after the first 5 min., but why does it have to keep auto adjusting through the ride.

Last night I was doing FTP 2x15 with a 5 min recovery after each one. I did them going up a 5-8% grade and then turned around and went back down for my 5 min recovery. When trying to get back up to the right power numbers it was very difficult, I guess because it recalculated tilt. After 5 min. into the 2nd interval it finally fixed itself and everything was fine.

Am I crazy or is this what takes place in the unit all of the time? If so can It be stopped? Thanks..

Clint

[Velocomp]

Please send your ride file to me.

[rruff]

The iBike can be "off" +-0.1% grade pretty normally when you shift weight and change positions, but if you are going up say a 7% grade this represents only ~1% power error.

I did notice something similar when doing the same kind of intervals, though. I checked the files afterward and noticed a pretty large variation in elevation gain for each interval, even though they were all identical. I don't know why the iBike was having trouble with this, but I guess the barometric/altitude sensor was getting confused.

[GWPOS]

John@ Velocomp

I noticed my batteries were low after the fact. So I replaced them and will see if it happens again. If it does I will post the ride file for you to look at. Thanks

[rruff]

This might be a little OT since I don't think it's an auto tilt cal problem, but it is the same sort of course and effort that the OP is referencing and I saw something odd as well.

I went back and looked at my data from a two sets of 4x5min hill intervals I did last summer, 1 week apart. These were done on exactly the same stretch of road. I did not mess with any resets (reset only at home before the ride), and just highlighted the intervals in the software after the fact. I used 250W to mark the beginning and end and checked to make sure the distance was always the same. The numbers below are from the software.

Elevation change (ft), Avg Slope (%)

326ft, 8.38%
318ft, 8.19%
312ft, 8.14%
312ft, 8.12% avg= 319.25ft, 8.21%

303ft, 7.91%
295ft, 7.72%
303ft, 7.82%
306ft, 7.93% avg= 301.75ft, 7.85%

The variation within each day was fairly small (~3%) and could be explained by variations in the barometric altitude sensor's accuracy and it's ability to set the proper tilt. The more puzzling thing is that the elevation gains and avg slopes were all lower on the 2nd day compared to the 1st day... by an average of ~5%. This would result in a power deviance almost this great. The reason I even looked at this was because I initially thought I'd done very poorly on the second day since my average power was much lower. However, after I normalized all the runs to the same slope, the avg power each day was virtually identical.

Any ideas what would cause this? Is there a reason why the barometric sensor would would misrepresent elevation changes by this much, from one day to the next?

This isn't an isolated incident either. On a longer climb (~42min) that I did weekly last summer, the average grade returned by the software for the identical stretch of road, was:

6.62%, 6.79%, 6.66%, 6.82%, 6.98%, 6.87%, 6.68%, 6.70%, 6.66%, 6.75%, 6.73%, 6.65%

The maximum deviation there is >5%.

[GWPOS]

I did not go and check all of my rides like you did but there is something strange that happens when doing hill repeats. I will have to check my workouts closer after I do them to see if I get a lot of variations in my power numbers, etc. I thought it was just me.

[lorduintah]

Are you getting the same elevation - day to day - or does this change and you are not correcting it to the same starting value? I know I have significant differences and I find it necessary to adjust the starting altitude quite often - and I am only 500 ft above sea level in Dallas. Some days the meter will start at 180 - others it is pretty close to ideal. Nothing predictable - except when I truly note a weather front comes in - see this effect during rides, too.

I have found some tilt averages that get up to 0.25 - if I change the altitude at the wrong time and the iBike thinks a ride has started. This can - at least for a while - throw off the wattage by a lot.

Tom

[rruff]

I always set my elevation before I leave the house, but even if it was off by 200ft I don't think this would have a substantial effect on anything.