The lion kingdom printed some smaller 90mm tires to get more climbing speed.  Tire designs are getting much softer & quieter, but not improving the traction.

These introduced a shroud to keep rocks out of the motors.  These reduced the maximum speed from 10mph to 8mph & didn't materially improve the climbing speed.  The other options were higher voltage batteries, expensive.  There was more windings of lower wire gauge, not enough room.  There was using bigger motors, very expensive & reduces ground clearance.  

The cheapest, most configurable option is a boost converter.  It's a way to use semiconductors to make a motor pass more current from a lower voltage.  The boost converter would allow the motors to be rewound again for higher torque & higher voltage or it could just be used to send more current through the existing windings.  The maximum torque is achieved with 70-80 turns of 32AWG, depending on room.  This requires over 40V to hit 10mph with a load, according to past notes.

The current winding is 20 turns of 26 AWG.  It achieves 10mph with a load, on 12V.  The boost converter might require more turns of finer gauge to manage the heating.  It reduces range by up to 20% depending on the load.