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I just bought a new Cannondale Synapse Carbon Disc SE 105 and I am having trouble with the chain dropping on gear 50-11.

If I shift on the front chain ring to the biggest ring (50t) and in the rear to the smallest one (11t), the chain drops to the outside of the chain ring under load after a while. If I rotate the crank manually without load I can see that the the chain is jumping up on the chainring teeth.

It seems like the front chain ring should be 2-3mm further outboard because the gear teeth catch the chain plates causing the chain to jump.

Does anybody have the same problem? Any tips how to solve it? It is not a problem with the high/low limits on the derailleur.

Thanks

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    I'm struggling to visualise what you mean, can you show it in a photograph? Also I would normally suspect the high limit screw on the derailleur, so can you clarify why you think this is not the issue? maybe if I understood the problem better I would see why too
    – Swifty
    Sep 18, 2019 at 19:49
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    You bought a product; it's not quite right. Take it back to the shop and get them to fix it and explain to you what the problem was.
    – David Richerby
    Sep 18, 2019 at 20:39
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    @Swifty my interpretation is that when in 50/11 the chain is arriving at the big ring at a slight inward angle, and the big ring teeth are catching on the inboard side chain plates causing the chain to climb on top of the teeth
    – Argenti Apparatus
    Sep 18, 2019 at 20:49
  • @DavidRicherby I would do that if it were easy but I bought it from online store in different country and that would cost me too much time. I took it to a local bike service and they flatten bent teeths and is ok now.
    – Bruce
    Sep 19, 2019 at 18:35

1 Answer 1

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The problem was that some ring teethes were a little bit bent. There have to be some impact somewhere between manufacturer and delivery service (the box was not damaged).

I took it to a bike service and they flatten these teethes and everything is now perfect.

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  • Yes, bent chain ring teeth can be a vexing problem. Note that you can accept your own answer, if it is the correct answer.
    – Rider_X
    Sep 19, 2019 at 20:46
  • @Rider_X Thanks, yes I know. But I have to wait 24 hours until it is possible.
    – Bruce
    Sep 20, 2019 at 12:49

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