You could probably get away with 14 but I wouldn't recommend it. If the esc/motor were to draw excessive amps it could cause problems, even melt or catch wires on fire. Again, amps are the issue here, it really depends how hard you are running your motor, timing/boost, and gearing that will alter how many amps you're drawing at a time. If its all you have and you're in a pinch you could test it and pull the car off early to feel the wire temps.