( I'm having problems with my running computer )

Bike gurus, I has query. I have a Polar S-Series Speed Sensor for my Polar S625x HRM. Works great with my road bike.

Trying to fit it to my MTB for winter usage, I am coming unstuck. I have to set a wheel size to enable it to do its funky stuff. Now, my MTB wheel says "ETRTO 17-559". I have a chart with the manual that starts at something like 30- ( Read more... )