it can be many things causing this to happen,one is did you have the drums and rotors turned or just replace the pads or shoes,secondly if the calipers do stick on it that to will cause it,but without seeing it i cant give you a direct answer to the exact cause of it,you,ll have to tear it back down now and start over with it,use a repair manual as a guide this might help you find the cause of that happening,the do have some helpful tips in them on that problem,good luck.