What would prevent the same air bubbles, from getting in the longest line If you had done that one first, and were pushing air out of the shortest line second?However in the worst case, where all lines are dry. If you were to start with the wheel closest to the master cylinder and bleed it until there is no air, and then moved on to the wheel furthest from the master cylinder, as you're pushing the air out of that longest branch you might get some air bubbles in the shortest branch that you just filled.