@enobacon They are adjustable, with a screw to adjust spring tension and the three holes on the post. Originally I had them all on the middle hole, but the return was not a much as I wanted so I moved them to the top hole (greatest tension), but then one of the arms apparently "failed" it still works, but a lot less tension, for that brake, I have the failed arm in the high tension hole and the working arm in the medium hole. Balances better (the screw on the failed arm does not change the tension). I don't see a way to disassemble the arm to see what is going on inside (other than destroying it).
They are Promax P-1 108mm arms. the 85mm arms I think would be just a few mm to short and the brake cable would rub on the tire. #BikeNite