The GSM creates enough back EMF to cut out at about 95 rpm. That is why I have decided to up the voltage a little. Seems to work on short test runs so far but need to try the big hill before making a serious opinion.So if you spin slower than the motor's optimum speed, then you waste battery power through winding heat losses.
But what happens if you spin your legs FASTER than the motors optimum speed? (so you're way above the power band and the motor is still spinning, but not giving much if any assistance)