[Al Skierkiewicz]

Ed,
You have demonstrated a classic issue with high friction wheels in a tank turn. The motor wires heating up is a sign that should not be ignored. If you were feeding the motors through circuit breakers, they would be tripping. As others have pointed out above, teams have discovered that raising/offsetting the height of the wheels prevents the incredible side load of all wheels on the floor. This cause each of the CIM motors into near stall current draws. At 129 amps each that is a total of 516 amps. You might have also noticed that the Crio is inhibiting output for a short period of time (if it is not rebooting). When the battery voltage falls to 5.5 volts, the Crio inhibits output in anticipation of a voltage fault. This causes a somewhat jerky motion during the fault. With a 516 amp draw, the battery will not be 12 volts no matter how well it is charged. You will drop voltage across the internal resistance of the battery that may take it down 5 volts or more.
Dr. Joe will give you some insight on design and as other have pointed out, wheel choice can have an effect as well.
If your motor wires were hot, the internals of the motor were hot as well. A "nose" check around the motors will tell you if you have stressed the motors.