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    My Tiagra derailleur broke off while swiching to lighter gears. Anyone can think of a reason?


    I was just downshifting at a traffic light, while turning left. Nothing crazy.

    36t casette, 11 speed, 10 speed freehub, 4700 tiagra GS RD.

    The derailleur was not new. The cage was previously bent and it took with it the derailleur hanger.

    My theory: Something must have lead to it getting caught in the spokes in the lightest gear. I never had issues with the chain falling, so I think that the limits were right.

    Maybe the cage got bent and the wheel flexed while turning?

    Edit: it looks a piece of a branch got sucked in the cage somehow…

    https://i.ibb.co/d0mjqTxk/20260315-201429.jpg

    1km away from a park? Weird. It must have fallen from the mudguard…

    by lakotamm

    View 5 Comments

    5 Comments

    1. ballpark-chisel325 on

      Are you positive it hit the spokes first? Because it could have torn off first. A torn off RD will always be hitting spokes one way or another.

      You do not mention chain getting off the largest cog biting your spokes, so my guess – it torn itself off before hitting the spokes. Culprit could be something as simple getting a tiny stone right onto the chain before the link engages with the pulley, it locks and you just pedaling tears off a derailleur no problem. Yes, this did happen to me once, too.

    2. Twig_Scampi on

      If you’re positive the low limit was set correctly then your hanger got bent at some point before the wreck.

    3. MartinFromMars on

      I had something like this a few months ago, but under acceleration from a full stop. The pin on the main pivot point of the derailleur snapped and threw everything into the wheel. The derailleur hanger and derailleur attachment to it were fine. The setup (Sora) had around 12k miles in them. I had put it down to bad luck and had to replace half the spokes.

      img

    4. camp_jacking_roy on

      Misalignment. I had a 105 derailleur that was shifting poorly before it finally disintegrated, taking the chain with it. A new hanger and derailleur and we were good to go. I suspect there was a slight misalignment in the hanger that caused the chain to catch and take the derailleur up into space with it.

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