Here is an illustration:
tie is measured from the center of the robot although it is displayed from the robots edge so we have:
( xx)xxxxxxx(xx )
now the tie length limit before it snaps is:
xxxxxxxxxxxx
if the robot is too big, say:
( )
then the tie will snap at any rate.
It is a little more complex then that, because this new explanation I just gave you has nothing to do with 'go negative.' But, it does if you look at the code.