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My road bike gear cables have never been replaced, they are 6 years old now. The shifting at the back needs at tune up now and then, more and more frequently as time goes. But once it's done the shifting feels nice, good as day one I dare say. I have ordered a set of spare inner cables. Shall I put them on ASAP or 'if not broken don't fix'?

I have a tiagra 4600, not the ones with the awful bends under the handlebars which I have heard awful stories about.

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  • 6 years, you've been teasing Fate. Do it! ;-)
    – Carel
    Commented Oct 2, 2021 at 21:18
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    I have a tiagra 4600, not the ones with the awful bends under the handlebars which I have heard awful stories about. I have read the comments here though and will replace the cable asap. Will report if shifting performance improves! Commented Oct 2, 2021 at 21:37
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    About how far do you ride this bike per year?
    – Criggie
    Commented Oct 2, 2021 at 21:47
  • I don't have a mileage counter but I have put some ~20k kilometers on this bike and cables (brake cables have been replaced after feeling spongy). Commented Oct 2, 2021 at 21:51
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    The cable housing has a teflon liner for low friction. Over time dirt will enter the housing and increase friction. The liner will also wear down. If the housing is routed in tight radii it can crack over time or break at the end caps. Plastic end caps can also break over time (or the steel strands of the housing poke through the plastic end cap over time). Abrasion against frame or other cables can also be a problem. If the housing looks flawless and shifting works great it probably doesn’t make sense to replace anything. But if it’s not you might as well replace it while you are at it.
    – Michael
    Commented Oct 3, 2021 at 11:43

1 Answer 1

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Inner cables tend to break relatively early after ~5000km depending on circumstances and how much you shift. I think it got worse with modern shifters with cable housing below the handlebar tape. The cable starts to break and fray inside the shifter.

Usually you notice because the rear derailleur doesn’t shift to the smallest sprockets anymore and it gets worse and worse until the cable snaps or completely seizes up.

So you have some warning and usually are able to ride home just fine. Getting the frayed cable out can sometimes be a bit of a hassle.

A rear derailleur with broken cable will shift to the smallest (hardest) sprocket which can be problematic for getting home. Cable ties can allow you to fix the cable in place so the derailleur stays in an easier (but fixed) gear. A front derailleur will shift to the smaller chainring which is usually fine for getting home.

If you are planning a longer trip and your cables are already used a lot it could make sense to replace them just in case. Otherwise I’d use them until they start to fail.

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    Also some designs of road shifters can be very hard to get the broken cable head out of, don't forget that!
    – Noise
    Commented Oct 2, 2021 at 19:58
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    @michael thanks for input. I must say I wasn't expecting gear cables to snap so commonly. In my head they take less stress than brake cables. Though they also are markedly thicker. Definitely feeling like I am learning valuable here, and which I will put to use briefly. Commented Oct 2, 2021 at 21:43
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    Shifter cables are coiled tightly inside the shifter which tends to break them over time. Brake cables shouldn’t suffer any sharp bents and can basically last indefinitely as long as they don’t rub anywhere.
    – Michael
    Commented Oct 3, 2021 at 5:52
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    @JoeK: Yes, which is why it can be a good idea to replace it before a long trip, even if you have a spare cable with you. Sometimes you need needle nose pliers, various screw drivers (or other thin, long objects), good light and lots of patience to get the head out.
    – Michael
    Commented Oct 3, 2021 at 11:20

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