I am using a dumb trainer + zPower (speed and cadence sensors)
It seems that when I get to a climb, Zwift recomputes my cadence to something much lower
Is that the expected behavior?
Is there any doc on how/why this copputation is done?
You cadence (speed at which you pedal) is measured by your cadence sensor and zwift display what it get from the cadence sensor.
Your game speed is calculated by Zwift using your speed sensor and a power curve of your trainer. Therefore you wheel speed and in game Zwift speed will be different.