Originally Posted by
billridesbikes
This thread has made me think about my Garmin. Ever since the 705 I’ve used ‘auto-calibration’ for the wheel size. I assumed that it counts wheel revolutions and compared it the to GPS and used this number as the circumference. But does anyone know exactly how this feature works? Does it do it continuously, once an hour, once a ride, only durning a setup? How many wheel revolutions does it use?
It does it once at the start of the ride for about 0.1 of a mile (from what I recall reading about it a while ago).
It gets the distance from GPS and calculates the wheel circumference based on the number of wheel rotations that occur during the time of the measurement.