Originally Posted by OldCoot
If the trailer breaks away and is being held by the chains, you want the trailer brakes engaged to keep the chains taut and not let the trailer ram into the tow vehicle causing more damage when you are trying to stop. You can leave them long and see what happens, but I have always shortened the cable to the make sure it was shorter than the chains.
I would have to agree with MtnGuy. If the brake cable needed to be shorter than the safety chains then the factory or at least the dealer should be doing something about it.
If the trailer became free from the vehicle the last thing I would want would be the full application of the trailer brakes of a 7000 pound (or greater) trailer pulling on the chains while the vehicle is pulling away. If the trailer is still attached to the vehicle then chances are the power cable is still connected and braking will be controlled by the tow vehicle once it applies the brakes.