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  1. #1
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    Upset Replace Suntour rear deraileur

    I new to the forum. I have an older mt. bike with a 7speed drivetrain from Suntour. The rear derailleur is broken and I need to replace it. It is a Suntour XC-comp.

    Are there any suggestions? Are any of the current line of derailleurs compatible with this this drivetrain?

  2. #2
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    Quote Originally Posted by Old Teal
    I new to the forum. I have an older mt. bike with a 7speed drivetrain from Suntour. The rear derailleur is broken and I need to replace it. It is a Suntour XC-comp.

    Are there any suggestions? Are any of the current line of derailleurs compatible with this this drivetrain?
    Finding a clean used or NOS Suntour XC-pro would be your best bet. They go on e-bay all the time, usually for less than the cost of a new Shimano LX.

    7-speed Suntour indexing uses inconsistent spacing across the freewheel, so only Suntour levers are likely to index with your freewheel. Suntour's actuation ratio was different from Shimano's, but I know people who have made Shimano derailleurs index with Suntour shifters. Try routing the cable to the other side of the pinch bolt.

    Or, put those sweet-shifting Suntour thumbies into friction mode, and use whatever derailleur you want.

    If you have a newer derailleur laying around, try it, it may work.

    --Shannon

  3. #3
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    Broken rear Suntour XC comp

    I new to the forum. I have an 1991 CADEX CFM2. The rear derailleur is broken and I need to replace it. It is a Suntour XC-comp. How do I know if it is a RD-XC20-GTB (short cage)-GXB (long cage). And where would be the best place to start looking for a replacement.

    Are there any suggestions? Are any of the current line of derailleurs compatible?

    Thank you!

  4. #4
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    Quote Originally Posted by tube_ee View Post
    7-speed Suntour indexing uses inconsistent spacing across the freewheel, so only Suntour levers are likely to index with your freewheel. Suntour's actuation ratio was different from Shimano's, but I know people who have made Shimano derailleurs index with Suntour shifters.
    When you say inconsistent, I'm thinking what you meant was that not all the spaces between cogs are the same width (which is the case with Shimano 7 & 8 speed, but to a lesser degree), rather than that Suntour didn't make the spacing the same for all of their freewheels. IIRC, the Suntour cassettes were more consistent, and 7 and 8 speeds used *exacty* the same inter-cog spacing, just with an extra cog on the latter.

    FWIW, I've successfully used Suntour 7 and 8 speed shifters and matching levers with Shimano 7 and 8 speed HG cassettes, on both road and mountain bikes. This is more likely to work than the reverse, but that may be possible too. Either way, the shifters should ideally match the derailleurs.

  5. #5
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    The floating pulley on the rear derailleur can often make up the difference which is why using Shimano cassettes might work OK.
    Former bicycle mechanic for 8 years, current soil scientist.

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  6. #6
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    ^ Fair call, except that Suntour derailleurs don't have a floating pulley by design, though there may be some slop. Only Shimano actually *designed* the top pulley to float laterally AFAIK. Still, as long as it works that's the main thing, and it does. (Perhaps because the HG cogs are happy to make the shift even if the derailleur isn't in exactly the right place. And Suntour engineered overshift into their levers too.)

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