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How to get access to wheel size estimation using speed sensor?

Hi,

I have made a couple of rides with different bikes, and therefore different wheel sizes. I know the speed sensor performs an auto calibration to get distance and speed, meaning it estimates the wheel size over time. But how can I check which wheel size values are used throughout the trip. I guess it varies over the trip so I wonder if you can get that information (as well as revolution counts) in the fitfile. I am interesting in this since I want to compare it with the real wheel size and adjust distance and speed accordingly for those trips, in order to get more accurate values.

I am using Edge 1040, and speed sensor 2

Thanks in advance for any tips.

Top Replies

Dan.Boilermaker 9 months ago +2

You have the option to set the wheel size manually. I always do this instead of relying on the auto-cal.

All Replies

0 Dan.Boilermaker 9 months ago

You have the option to set the wheel size manually. I always do this instead of relying on the auto-cal.

0 Cranky K. 9 months ago in reply to Dan.Boilermaker

For the low cost involved, in my opinion it's most practical to have a wheel speed sensor for each set of wheels. Also, as per Dan.Boilermaker it's best to manually enter the value for each speed sensor. It is very easy to lay out a tape measurer and roll out the wheel and achieve a very accurate circumference.

0 memopc89 9 months ago in reply to Cranky K.

Yeah. In the future, I for sure will set it manually. However, I am interested in looking into those rides I've already made on auto calibration.

0 Skordilovich 9 months ago

What wheel size you have?

0 memopc89 9 months ago in reply to Skordilovich

One is 2080, the other one is more like 2280. In speed sensor details, a value of 2136 is shown. Does this value change in every trip? Is this value used across the entire activity or is it constantly changing during the activity? If the latter is the case, then I guess the distance/speed error should be larger in the first kms right? Or how long does it usually take to get a "good enough" estimate of the wheel size (assuming riding on flat roads)?

0 Dan.Boilermaker 9 months ago in reply to memopc89

memopc89 said:
Does this value change in every trip?

No, one time calibration after paining with your device.

memopc89 said:
Is this value used across the entire activity or is it constantly changing during the activity?

Once calibrated (manual or auto), it never changes.

memopc89 said:
how long does it usually take to get a "good enough" estimate of the wheel size

Based upon GNSS signal. The GNSS is used to measure distance and applies the distance vs. rotations to calculate the wheel circumference.

As mentioned above, just get a second speed sensor or leave on the bike you use most.

0 Skordilovich 9 months ago in reply to memopc89

700 × 28C it is 2136. But in my case i put it manual cause in auto speed sensor puts 2105

0 memopc89 9 months ago in reply to Dan.Boilermaker

It does seem to change in every ride I make in auto mode, I've seen even small changes with the same bike. Is there a way to access the calibrated wheel size value for previous trips? Is it stored somewhere in the fitfile?

0 memopc89 9 months ago in reply to Skordilovich

Happens to me too, I do get estimates below the "real" one. It sure depends on tire pressure etc, but hard to say how much difference can you expect because of this.

0 aweatherall 9 months ago in reply to memopc89

It is stored, but only at the start and end of the activity so you don't know what it was all the time. Typically I set the size manually so that the value is static.