Nosediving Neus

[Serum]

that's annoying. You can't get used to that.

And also plastic spur felt smoother maybe because its quieter

It's not said that silence means more efficient; remember, plastic is an acoustic absorber.

I don't understand your graphics; the only thing that could make a difference is the cg, it has nothing to do with binding, unless the motor (pinion) and the spur are not parallel.