no you cant. to break you need to block your torque wheel (either the left, the right one or both). all other wheels are just here to roll on but they dont do anything. usually the torque wheel is always a bit elevated as you can see here:
http://i40.tinypic.com/i22fqc.jpg
this torque wheel is needed to BREAK and to ACCELERATE. i dont know how the old tanks worked but i know how the good old m113 works (i drove one in the military ->
http://i40.tinypic.com/35ivkzr.jpg). there are disc brakes on each of the torque wheels. now to turn your tank lets say to the right you need to pull on your right radius lever (i dont know the word in english sorry) which activates the disc brakes on your right torque wheel and slows it down --> the right track slows down -> your making a right curve.
you can also turn your tank while its not moving. the m113 also cant move both tracks in the oposite direction. you have to pull another lever, which completely activates the disc brake and blocks one torque wheel (left or right
) now with the on track locked hit the gas and your tank will perform a turn on the spot.
you cant perform this with one track broken because you dont have tension on your track. so no, you cant break without the track.
i also made a nice little illustration
:
http://i39.tinypic.com/4rxhkp.jpg