MA makes hardware that attaches left to right across the back of the rack that has slots for attaching cable ties.
At the very least, screw ties -- cable ties that end in a hole large enough for a #10 screw-- can attach to the back posts, supporting the wires.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
