First time replacing cable routed through frame
I have a 2021 Giant Defy Advanced 2 with about 6000 miles on it. Shimano 105 mechanical 11-speed. After struggling to get my shifting adjustments dialed in, I pulled back the brifter hood and found the cable badly frayed.
The shifter cables are routed through the CF frame, I have never worked on this before. I have 2 questions:
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I only ordered replacement inner cable (Shimano Optislick 1200mm). Is this going to be an acceptable repair, or do I truly need to replace the small lengths of outer housing? To my untrained eye they look good, with no visible corrosion, and I really didn't want to undo my handlebar wrap.
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What's the trick for running the new inner cable through the twists and turns inside the frame? I snipped off the frayed part of the old cable but did not remove it yet. I was kind of hoping there was some trick like fishing electrical wire, maybe joining the new cable to the old one with a length of heat-shrink tubing and pulling it through? Is that possible, or will even that small increase in diameter get hung up on something inside?
My LBS can't give me an appointment for at least 2 weeks, and I really want to learn to DIY this and get over my fear and ignorance of internally routed cables. Would appreciate any advice.
Posted Mar 8, 2026, 6:02 PM UTC