In everyday life and in the technical fields we often discover that certain decisions are based on “scientific data” when, in fact, they are often founded on historic conclusions that have not been challenged or re-evaluated in a long time. One such common myth is that for a stable and well-tuned drive you should match the motor’s inertia to the load inertia, which is typically done using a gearbox. Two factors lead to that conclusion: a. there is an optimization formula using the time constant of the motor and the load torque that shows that the best acceleration will be achieved if the reflected load inertia matches the rotor inertia; and b. a PID controller, which was commonly used when electric servos entered the marketplace, tend to perform best and appear to be most stable when the inertia are close or matched.