Why do you think your friend's bk is a problem?
Unless your friend's intention is to surrender the vehicle he/she is going to continue to make the payments so that he/she can keep it. Do you know what his/her intention is?
Unfortunately, if your friend does not reaffirm/retain (pay for) the vehicle your "right" is to make the payments as you agreed to do by co-signing. Alternatively, as AJ suggested, you could look into filing bankruptcy.
Never a good idea to cosign for anyone.
Des.

