I am going to try and take a crack at this, I may be wrong but from my experience: I use amp draw to gear a motor. Lower amp draw=higher gearing, higher amp draw=lower gearing. When breaking in our motors at 2v w/o a breakin fan, they are unloaded. So they are spinning their maximum rpm's at whatever amperage. For tc's you want the amperage to be higher because they pull more amps than say a 1/12th scale. The reason being that if you look at amp steps on a dyno readout you will see that as the amp draw gets higher the rpm's get lower. So you want the motor to pull more amps at its maximum rpm. Giving you more rpm's out of the corners and such. At the end of a straight when your motor is only pulling 10 amps or so, with a motor that pulls 10 amps unloaded, you are getting maximum rpm's. With a motor that only pulls 6 amps unloaded you are not getting your maximum rpm's yet. However this is subjective. If your motor isn't efficient enough at higher amp draws then it will do you no good (it will rob you of power, causing you to draw more amps). With 1/12th scale however I look for less amp draw from my motors. Good range in my experience, tc: 8.5-9.5. 1/12: 6-7. Again, I may be wrong but this is what has worked for me.