slipstick:
Those ESCs work in either forward only or forward/reverse mode. It sounds like yours is in forward only. You need to program it for the other mode.
If you look at the manual here:-
http://www.hobbywing.com/products/enpdf/QuicRunWP1625-WP860-WP1060.pdf
You'll find it's a little more complicated than that. The ESC has three operating modes Forward/Brake/Reverse, Forward/Brake and Forward/Reverse. The default setting is Forward/Brake/Reverse. This requires what the manufactures call a "double click" action to go from forward to reverse. For this the throttle is taken to reverse and the motor starts to slow down, then throttle is taken back to the neutral position and once the motor stops it can then be driven into reverse.
For testing and use in a tracked vehicle the OP should probably switch the ESC into the Forward/Reverse mode (this means changing the links on the unit).
Ian