Use a small spring. Connect it to the line then the other side to the frame or what you feel like is a good location. When in flex the spring will flex and give , when not flexed or under compression the spring will pull the line back.
GCM 2 said:Chris, here is a photo of my rig immediately after I picked it up from Off Road Evolution. You can see my front brake lines are zipped tied to the corrugated wire loom the wheel/abs sensor runs through.