How to Install an Ultegra Dual Shifter Cable
- 1). Place your bike in the work stand and clamp it in securely. Shift the rear sprocket into the smallest (or, if you were riding, hardest) gear. This would be the sprocket closest to the rear derailleur.
- 2). Disconnect the cable at your rear derailleur using the 5 mm hex wrench. If you're not sure what cable this is, follow the cable that is on your top tube down to the rear derailleur to make certain you're disconnecting the correct one.
- 3). Remove the shift cable by working it from the rear of the bike to the front, removing it at the shift lever. For a complete removal, the shift/brake lever needs to be depressed slightly to expose the cable nipple and get it out of the socket.
- 4). Remove both the inner wire and the rubber washers that protect your frame and discard.
- 5). Lightly lubricate your new wire and insert it, starting at the same shifter that you removed the old wire from. Make certain the nipple seats in the socket when you pull the wire all the way through so the excess wire is toward the rear of the bike.
- 6). Route the cable down the top tube and toward the rear derailleur, making certain that the rubber washers are replaced on the top tube, protecting the frame.
- 7). Install the end of the shift cable into the rear derailleur, tightening it with the same 5 mm hex wrench.
- 8). Leave roughly 2 inches of cable, with the rest of the cable being as taut as possible, and cut the rest with cable cutters. Add an end cap to the newly cut end of cable and crimp it into place with cable cutters, securing the end cap to the new Ultegra cable.
- 9). Check for looseness after two weeks of riding, as a new cable will stretch. If it is no longer taut or shifting has worsened, loosen the rear derailleur nut with the 5 mm hex wrench and pull the cable tight and re-tighten the nut.
Source...