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  1. #1
    Junior Mint jimn's Avatar
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    STI with Suntour cranks - front derailer adjustment

    Hello!

    I am attempting to use a Shimano RSX (600) front derailleur and brifter with a SunTour Cyclone double road bike crank.

    I have moved the front derailer to be about 2 mm above the largest chainring, and adjusted the low stop so that shifting down to the small ring works fine.

    Shifting up is more of a problem.

    If I adjust the high stop and the cable tension so that I can actually shift onto the big ring (52 tooth, no ramps), it sometimes overshoots and the chain falls off.

    If I adjust the high stop so it never falls off, it also won't shift into the big ring.

    It NEEDS a bit of over-shoot for the chain to grab the big chainring.

    There seems to be no in-between.

    Would using a Shimano crankset make a difference? Do I need new chainrings? The chain is new.

    Thanks!
    -Jim

    P.S. Sorry I used the word "brifter".
    Last edited by jimn; 06-18-09 at 12:36 PM.

  2. #2
    Senior Member
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    You do realize that there is a high stop too, right? Adjust it in far enough to prevent overshifting. There is a sweet spot where the shift will be easy, quick, and not throw the chain. What shifters are you using anyway?

  3. #3
    Junior Mint jimn's Avatar
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    Yes, the high stop is what I meant!!

    Original post edited.

    ANYway, that sweet spot is what I'm saying doesn't exist. It either throws the chain or won't shift at all, because it seems to need to push the chain past the outer chainring a bit to engage.

  4. #4
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    Adjust your front derailler lower.

  5. #5
    Junior Mint jimn's Avatar
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    I don't think it can go any lower without rubbing on the big chainring. It's about the width of a nickel off.

  6. #6
    Senior Member
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    What chain are using? Any chance you are using a 9 or 10 speed chain? Have you verified that the derailler cage is parallel to the big chainring?

  7. #7
    Great State of Varmint Panthers007's Avatar
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    As with any FD that misbehaves - the easiest fix is to uninstall it and start over. Seriously, this takes less time than trying to adjust the FD on the bike. Once (or if) an FD starts to screw up, each adjustment tends to cascade - knocking more and more things out of adjustment.
    How do you keep an idiot in suspense?

  8. #8
    Junior Mint jimn's Avatar
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    joejack951: Pretty sure it's the right chain. I'll check that.

    Panthers007: Not a bad idea.

    But I'm surprised nobody's mentioned the two things I would have thought it was:

    * the chainring isn't ramped

    * the Cyclone cranks have the wrong spacing between the chainrings

  9. #9
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    Quote Originally Posted by jimn View Post
    But I'm surprised nobody's mentioned the two things I would have thought it was:

    * the chainring isn't ramped

    * the Cyclone cranks have the wrong spacing between the chainrings
    I haven't mentioned them because I've used older cranks without ramped/pinned chainrings with STI (Sora) and had no problems getting it to shift ok. With that said, upshifting does require a slight delay of the shift lever motion for the shift to complete. Whereas with ramped and pinned rings you can just quickly push the lever to shift then let go and the shift will complete, without the ramps and pins you need to hold the shift lever in for a half second then let go. Does this make sense?

    For some reason, I blanked out on this until it occurred to me this morning.

  10. #10
    Senior Member vredstein's Avatar
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    Is your setup (rings, cogs, chain, shifters) a 6,7,8,9, or 10-speed?
    I'm running a 9-speed setup with Cyclone cranks, no-ramp Suntour ring, 9-speed SRAM chain, 9-speed downtube shifter, and Ultegra derailleur without issues.
    "See, it's not that getting wet is a big deal. Really, it's what you're getting wet with.
    Fenders....because it's probably urine."
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  11. #11
    Junior Mint jimn's Avatar
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    Thanks for all the good info.

    It's a mystery why it doesn't engage. I'll have to take another look at the whole thing.

    You guys have definitely saved me some money buying Shimano cranks.

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