Internal routing is one of new technologies which Asama applies to sporty bikes because these bikes usually are ridden at high intensity. The shifter and brake system of sporty bikes works constantly so it need to be good while your ride usually exposures to the environment. It also protects a cable as well as give an aesthetics.
To limit an external effect to the cab, a frame will be applied internal routing technology in order to create more hole to put the cable into the frame.
There are 2 frame types which contain the internal routing cable. There is a lightweight frame for the bike road so the cable is not covered by the case. The another one is for the terrain bike. You can put the cable which is covered by the case into the frame because the holes on the frame are bigger.
The internal cable routing gives the bike more aesthetically pleasing option, and helps protect them from contamination.
For the technology aspect, the cable will be shielded from contamination such as: dirty and dust, which stuck on the shifter cable. So the shifter and the brake do not work smoothly. The terrain bike which is usually ridden on the unpaved, its shifter and brake cable is broken easily. Therefore, most of terrain bike will be applied this technology. As well, the shifter and brake cable will be used over the long term, which does not take a long time to maintain and lube it up.
For the aesthetics aspect, if the cable is in the frame, the bike will be nice and neat.