PM motors do have cogging torque, or zero current torque, due to the interplay of the magnets. Bikes have so little regen efficiency that it usually makes sense to just install a freewheel. Some other sort of clutch (or neutral) will eliminate it too.
Reduction of cogging torque in permanent magnet machine
This is readily apparent in my prius, in order to "coast" the car, I have to feed the motors about 10 amps.