Internal cable routing.

[GrasB]

Apart from the fact that cables routed under the tape are no more exposed to the air than those that go inside the bars there is no drag from brake or gear cables anyway. The air that doesn't hit an exposed cable will get you full in the chest a couple of inches further back.

Not quite true. The way the brake cable exits the bar(tape) is important. A sorted internally routed cable will exit more cleanly & be heading towards the back of the bike/has a shrouded exit so air flows cleanly over the cable exit. This results in dramatic drag reductions at the cable exit which is where the majority of drag caused by the cable is (loads of turbulence) assuming that you have aero tops (which is one of the primary reasons for internally routed cables) a non-taped tops is much more aero than a wrapped top with cables. As I said you're getting into the details.

 

[Angelfishsolo]

Not quite true. The way the brake cable exits the bar(tape) is important. A sorted internally routed cable will exit more cleanly & be heading towards the back of the bike/has a shrouded exit so air flows cleanly over the cable exit. This results in dramatic drag reductions at the cable exit which is where the majority of drag caused by the cable is (loads of turbulence) assuming that you have aero tops (which is one of the primary reasons for internally routed cables) a non-taped tops is much more aero than a wrapped top with cables. As I said you're getting into the details.

Sounds more like marketing speak than reality TBH. Then again if you are a top flight cyclist where m'seconds count maybe there is something to it.

 

[GrasB]

Sounds more like marketing speak than reality TBH. Then again if you are a top flight cyclist where m'seconds count maybe there is something to it.

On a properly setup fully aero bike (excluding the rider) the round cables are one of the biggest drag generators... I know this is talking about spokes but it gives you the basic idea about the difference between round top v's aero top bars

but also to quote my self I think that's kind of what I said...

So in the realms of the last 0.5% of gains that gets you that extra wheel length in the final sprint, for mere mortals not something that's too important, but not quite in the realms of hand picked bearings to gain 0.5w at 30mph.