With modern lined brake cable housing bend radii can be considerably tighter than if using older unlined housing w/o getting excessive drag. Standard routing is along the inside curve of drop bars , exiting from under the bar tape near the stem. Most modern bars have a depressed area for routing the brake cable, and sometimes the shifter cable, in that area.
Any good modern road bike manual, or the Park Tools web site, should show this.
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Gear Hubs Owned: Rohloff disc brake, SRAM iM9 disc brake, SRAM P5 freewheel, Sachs Torpedo 3 speed freewheel, NuVinci CVT, Shimano Alfine SG S-501, Sturmey Archer S5-2 Alloy. Other: 83 Colnago Super Record, Univega Via De Oro
Visit and join the Yahoo Geared Hub Bikes group for support and links.
http://groups.yahoo.com/group/Geared_hub_bikes/