That depends on the motorcycle you are working on, My 2018 heritage might be able to go 1"

 

When I swapped out the drag bars on my 2016 Breakout with a set of 2017 Fatboy-S bars there was plenty of length in the wiring (as the excess is folded up alongside the frame rails under the tank). As was the clutch cable. Now the upper brake line was a different story. I had to put on a longer (35") one. Interestingly enough there is still a few inches of cabling under the tank for taller bars/risers if I need it later on.