In this final installment of the full cable replacement series, we’re going over shift cable routing.
The process has actually been mostly covered in previous posts, and part 2 of the series has a guide to threading the cable housings through the downtube. I’ll be discussing only the areas where there is most difference from the rear brake cable replacement job.
In the photo above, the two shift cable housings actually share one cable routing hole, unlike the brake cable housing which has its own, off to the side. Making matters worse, this is a tight fit. I had difficulty with fitting the Park Tool IR-1’s guide cable magnet ends through this hole while it still contained one cable housing, and is otherwise still hooked up to the relevant derailleur via the inner cable.
This is why I recommend replacing the downtube-routed shift cable housings at the same time. While the shift cable housings are empty of a shift cable, you can play and finagle with them so that the IR-1 guide cables can thread into the downtube properly.
Above are the shift cable housing segments. The long segment runs through the downtube, joining the in-line barrel adjuster floating around the head tube area and the relevant cable stops. It is pretty much the same length for both front and rear derailleur, since they all terminate around the bottom bracket shell area.
At the bottom of the downtube, both shift cable housings also share the same cable routing hole.
Thread the housing segments one by one through the downtube, and hold off on the shift cables until they are both routed cleanly through.
Here’s the result. The cable housing in the background arcs backward toward the rear side of the seat tube, where a cable stop awaits for the front derailleur. The cable housing in the foreground feeds into the drive-side chainstay, where a different cable stop awaits…one with a cable liner in it. Both these cable housings need ferrules on their ends.
As before, once the shift cable housings are correctly routed, the replacement job is 90% complete. All that’s left is to complete the rest of the rear shift inner cable routing, hook up STI levers with derailleurs, and tune properly.