crimson eagle has hit the nail on the head on this topic. The main concern is the ampacity of the wire since all of the losses are related to current, actually current squared times the resistance equals the power lost. Or. Voltage drop squared divided by the resistance OR The current times the voltage dropped. These are all the same by way of Ohms law. There is a point of diminishing returns when it comes to wire size, but I don't know what it is. 12 awg is good for pretty much everything we do in rc sedans. I do know boat racers that will use 8 or 10 awg, but they draw more current than a sedan ever could. More cells, high power brushless motors.... etc. The other thing that needs to be considered is how much current can be carried by the wire used to wrap the motor. 120 Amps?!?! Probably not for more than a second, probably less. This is especially true for a stock motor where there is 1 piece of 24 awg wire wrapped 27 times. Also, if a battery pack has .006 ohms of resistance (6 milliohms) the battery voltage at 100 A would be 8.0 V (fully charged batteries have more than 7.2 volts) minus (100 * .006) , or 8.0 - 0.6 = 7.4V. Compared to this the wire for the connections is tiny. The soldered connections to the battery and motor will have more resistance than the wire itself.