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  1. Looks like a standard Shimano indexed downtube shifter boss to me. I’m looking at an old set of Dura-Ace 9 speed downtube shifters, and it looks like you just need to pop off the concave washer and it’ll slot right in.

  2. rivalpinkbunny on

    Is that a cannondale? I forgot what it’s called, but I hate that shifter boss. They screw into one another from the opposite side because it’s before they figured out how to weld aluminum shifter bosses into the downtube. That means that they back out and unscrew while you’re riding, which is lame. (And if anyone has a solution, I’d love to hear it.)

    Mine work with Suntour shifters, and I’ve had luck getting them to work with others, but not without shimming them.

    Edit:

    Here’s what it looks like disassembled (and upgraded):
    https://www.improvepart.com/products/cannondale-downtube-shifters-bosses-adapter-44mm-31-8mm-28-6mm?gQT=2

  3. Look into Shimano part #Y64343000. That should get you going in the right direction.

    To answer your question: it isn’t well named. “Flat-back” vs “curved-back” is about the best nomenclature on it I’ve seen. But yeah, there were two different boss types. A different boss plate should get you back in business.

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