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  1. #1
    ass hatchet slopvehicle's Avatar
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    steel-era downtube shifters on modern aluminum frame?

    I picked up a Performance / Nashbar aluminum road frame on the cheap. My plan is to turn it into a commuter / beater, since I have some clunky parts to spare.

    I've got a set of Shimano RX 100 downtube shifters from the early 90s that I intended to use. However, when I install 'em, the mounts seem to fit poorly-- the inside curve of the chrome shifter plate (the part that contacts the frame) seems intended for smaller gauge tubing. The Al downtube on my frame isn't especially oversized, but apparently it's enough to make the shifters not seat very well against it.

    Am I out of luck? I really don't want to spend a lot of money to get this project rolling.

  2. #2
    coprolite fietsbob's Avatar
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    Steel era is not over..

  3. #3
    ass hatchet slopvehicle's Avatar
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    Quote Originally Posted by fietsbob View Post
    Steel era is not over..
    Believe me, I know-- this is the first aluminum frame I've owned in a long time.

    Anyhow, I think I answered my own question by searching elsewhere: I'm out of luck.

  4. #4
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    You are talking about the curved plates that go on before the shifters right? Some of the larger diameter tubed bikes (i.e. old Cannondales) used the elusive shallow curve plates.

  5. #5
    ass hatchet slopvehicle's Avatar
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    Yeah, it makes sense that the shallow plates are out there somewhere. But It's not what I've got...which is a bummer.

    Didn't anticipate this challenge when I began assembling the project in my mind. The RX 100s were purchased on the cheap for a different frame, now sold.

    I have some Campy friction shifters that might work, but I was hoping for an indexed 1x9 commuter setup.

  6. #6
    aka: Dr. Cannondale rccardr's Avatar
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    The Cannondale plates are an option if your DT is drilled to accept them- no other way for them to work. Then you will need to take those curved pieces and make them flat- a Dremel and a grinding stone do the job very quickly since they are pretty soft. If you already have mounts brazed on, then you can re-radius the trim pieces with a Dremel- just take your time and do it slowly.
    Hard at work in the Secret Underground Laboratory...

  7. #7
    Classics lover rob_g's Avatar
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    Quote Originally Posted by slopvehicle View Post
    I've got a set of Shimano RX 100 downtube shifters from the early 90s that I intended to use. However, when I install 'em, the mounts seem to fit poorly-- the inside curve of the chrome shifter plate (the part that contacts the frame) seems intended for smaller gauge tubing. The Al downtube on my frame isn't especially oversized, but apparently it's enough to make the shifters not seat very well against it.

    Am I out of luck? I really don't want to spend a lot of money to get this project rolling.
    I have the same shifters, part of the complete group set on my Bianchi. It works wonderfully.

    Had been looking for a more modern 8 speed Shimano indexed shifter, and noticed they are available in two model numbers - one with the more rounded flange mount, like yours; and a variant where the mount is a lot flatter, described as for modern, large diameter frames.

    The one you have could be ground down (the horror!) a bit, to make it fit better. Careful work with some files could be the answer.

    I was going to buy that 8 speed shifter, with the flatter mount, only because it was cheaper - about $33 (for the 'modern frame' version) versus $42 or so for old school. I would be swapping the mount with one of the older ones I have from other bikes, since I need the old style one.

  8. #8
    Senior Member
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    Quote Originally Posted by rob_g View Post
    The one you have could be ground down (the horror!) a bit, to make it fit better. Careful work with some files could be the answer.
    It's not a horror, it's easy. Place the bases curved side down on a flat sheet of sandpaper and sand them until they fit.

    I have a set of 8-speed Shimano dt shifters mounted on Kelly Take-Off adapters that require a completely flat base mounting plate. Chris Kelly used to supply these by taking regular mounting plates and grinding them down. They work fine.

  9. #9
    Classics lover rob_g's Avatar
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    Quote Originally Posted by HillRider View Post
    It's not a horror, it's easy. Place the bases curved side down on a flat sheet of sandpaper and sand them until they fit.
    That sounds like a great way to do it, HillRider. Good tip!

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