After using SRAM XX1 AXS wireless 1x12 MTB gears for the last five years I have just switched over to Shimano Deore XT M8200 Di2 wireless 1x12 MTB gears. These are paired to my Garmin Edge 840 v29.22 firmware.
With 1x12 MTB gears there is only a single front chainring. No options appear to customise this appear in the Shimano etube Project Cyclist app. The Shimano gears automatically sends both front chainring and rear sprocket sizes to the Garmin.
In the Garmin Edge 840 menu - Sensors - Shimano Di2 - Sensor Details are options to either leave the chainring or sprocket sizes on Auto default or manually enter sizes. When viewed on the Garmin Edge 840 screen whilst riding either of these options works. The front chainring size (39 tooth if left on Auto or my actual 35 tooth size when set to Manual) is shown in the Gear Combo screen on the Garmin. That's all fine.
The issue is that the front chainring size with Shimano Deore XT M8200 Di2 wireless 1x12 MTB gears doesn't appear to be being saved into the Garmin .fit file. Rear Gear Sprocket Size is saved into the .fit file but there is no front chainring, which then breaks the Time in Gear summaries and other reports for programs such as WKO5.
Although there is usually no front chainring saved it will occasionally appear mid ride however! This is only if I've stopped mid ride and paused the Garmin recording for several minutes. Upon restarting the recording and starting riding again a chainring size (not the correct one) will then be saved into the .fit file for the rest of that ride.
This appears to be just a problem with having the Shimano Deore XT M8200 Di2 gears paired. With my previous SRAM XX1 AXS MTB gears, and the exact same Garmin Edge 840 on the same v29.22 firmware, a front chainring size would always be saved into the .fit file throughout every ride.
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