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  1. #1
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    How to shift to big ActionTec ring?

    I got a set of ActionTec titanium rings (20,32,44) to replace the rings on my aging XTR-970. Neither I nor my mechanics can get my XT derailleur to shift from the medium ring into the big ring. One thing that puzzles me is that there are no ramps, screws, or anything else on the big ring for the chain to grab onto to help it into the big ring. The XTR rings have all manner of distortions on the inside to make for magically smooth flawless shifting by helping the chain up to the big ring. The ActionTec ring is smooth as glass and so the derailleur just mashes the chain up against the big ring without any way of lifting it up.

    Any suggestions?? I'm desperate. We're talking about filing some ramps on the inside of the big ring to help it up or putting some screws in the inside of the big ring.

    This bike has to perform flawlessly in about a week for a 2,800 mile race....

    tia,
    Russ

  2. #2
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    Quote Originally Posted by russmcb View Post
    I got a set of ActionTec titanium rings (20,32,44) to replace the rings on my aging XTR-970. Neither I nor my mechanics can get my XT derailleur to shift from the medium ring into the big ring. One thing that puzzles me is that there are no ramps, screws, or anything else on the big ring for the chain to grab onto to help it into the big ring. The XTR rings have all manner of distortions on the inside to make for magically smooth flawless shifting by helping the chain up to the big ring. The ActionTec ring is smooth as glass and so the derailleur just mashes the chain up against the big ring without any way of lifting it up.

    Any suggestions?? I'm desperate. We're talking about filing some ramps on the inside of the big ring to help it up or putting some screws in the inside of the big ring.

    This bike has to perform flawlessly in about a week for a 2,800 mile race....

    tia,
    Russ
    Find a new, older mechanic. Just need to set the FD correctly.

    Ramps and pins are a shifting aid, not needed for shifting as proved by nearly 100 years of previous use.

    No matter what you do the bike will not be flawless for the entire 2800 mile event.
    mtbtires.com
    The trouble with common sense is it is no longer common

  3. #3
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    Agreed, 100's of years of successful use, etc. FD's aren't that complex and between me and my mechanic we've adjusted a few hundred no doubt. Hence, my bafflement. The FD is set (height, rotation, limit screws, indexing) as it *should* be. Apparently, I now need to do something that I would *not* normally do to get it working. The question is what--?? I suppose I'll just start randomly messing with things beginning with the FD height. Any suggestions appreciated.

    The only time I've had an FD problem was with a SRAM Red FD and a Felt DA TT frame. Ultimately, I think it turned out to be a slightly warped FD that I wound up brute-forcing into alignment. My XT FD, however, seems perfectly aligned right now...

    Yeah, I expect some problems in the course of 2800 miles, but I want to minimize the severity and number of problems beforehand as much as possible.

    cheers

  4. #4
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    Quote Originally Posted by russmcb View Post
    Agreed, 100's of years of successful use, etc. FD's aren't that complex and between me and my mechanic we've adjusted a few hundred no doubt. Hence, my bafflement. The FD is set (height, rotation, limit screws, indexing) as it *should* be. Apparently, I now need to do something that I would *not* normally do to get it working. The question is what--?? I suppose I'll just start randomly messing with things beginning with the FD height. Any suggestions appreciated.

    The only time I've had an FD problem was with a SRAM Red FD and a Felt DA TT frame. Ultimately, I think it turned out to be a slightly warped FD that I wound up brute-forcing into alignment. My XT FD, however, seems perfectly aligned right now...

    Yeah, I expect some problems in the course of 2800 miles, but I want to minimize the severity and number of problems beforehand as much as possible.

    cheers
    "back-in-the-day" we use to "adjust" the FD cage with channel lock pliers. Bending the plate to lift or push the chain at the troublesome spots.

    I would also try a different chain. It may be too laterally flexible.
    mtbtires.com
    The trouble with common sense is it is no longer common

  5. #5
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    Yeah, I'm almost at the bending-the-FD stage.

    After a lot of inspection, it appeared that the chain was getting jammed *under* a bulge on the inside pushing side of the FD, preventing it from moving up and onto the big ring. It looks like the FD is constructed so that the chain is level with (and basically inside) a channel in the FD when in the middle ring and level with that bulge when in the big ring. I futzed around a bunch and eventually moved the FD up to about 10mm above the big ring, instead of the normal 1-2mm. This drives the chain against the FD bulge rather than jamming underneath it when shifting into the big ring. I also filed two ramps into the big ring (which was non-trivial in a Ti ring) to help the chain lift up. Tada! Working shifting!

    That was weird.

  6. #6
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    Quote Originally Posted by russmcb View Post
    Yeah, I'm almost at the bending-the-FD stage.

    After a lot of inspection, it appeared that the chain was getting jammed *under* a bulge on the inside pushing side of the FD, preventing it from moving up and onto the big ring. It looks like the FD is constructed so that the chain is level with (and basically inside) a channel in the FD when in the middle ring and level with that bulge when in the big ring. I futzed around a bunch and eventually moved the FD up to about 10mm above the big ring, instead of the normal 1-2mm. This drives the chain against the FD bulge rather than jamming underneath it when shifting into the big ring. I also filed two ramps into the big ring (which was non-trivial in a Ti ring) to help the chain lift up. Tada! Working shifting!

    That was weird.
    I would try a different model FD.
    mtbtires.com
    The trouble with common sense is it is no longer common

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