How to route cable housing for aero road bars:
Start by cutting housing long and using a pair of needle nose pliers to bend the tip of the housing. This helps get housing through the internal bend smoothly and directed to the exit port near the handlebar clamp. It is almost always better to start at the drop and end at the bar clamp to get the job done smoothly.
If the housing doesn’t pop out of the cable housing port all by itself, a flashlight and a pick tool are usually all you will need to guide it out of the hole. Once you get the housing through the bar, cut the housing to length being sure to cut off the bent section of the housing.