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10 speed chainring on a 9 speed crank?

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  • 29-08-2017 11:24am
    #1
    rflynnr
    Registered Users Posts: 984 ✭✭✭


    Boards hive mind: I have a 9 speed Tiagra triple crank. I'm replacing (with new for old) the cassette and chain but as the large and small chainrings on the crank are basically fine I only need to replace the middle one. However, I can't seem to find a 9-speed chain ring. Is there any reason to think a ten speed chain ring would present any difficulties for me?


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    #2
    Donnelly117
    Registered Users Posts: 1,509 ✭✭✭Donnelly117


    I believe the width of the chain is different between a 9 and 10 speed... So while it should work it may wear chains faster...

    Im open to correction on this though!


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    #3
    cdaly_
    Registered Users Posts: 6,440 ✭✭✭cdaly_


    I suspect the ring will wear faster as it's thinner than a 9sp. I have a suspicion that shifting from small to middle will be poorer but I don't know how much.


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    #4
    Plastik
    Registered Users Posts: 2,980 ✭✭✭Plastik


    Suboptimal bit should probably work is my guess. The only real problem I would foresee would be if the width of the spider arms changed slightly between the 9 and 10 speed systems which may mean that your current chainring bolts are either too long or too short.


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    #5
    magicbastarder
    Moderators, Category Moderators, Arts Moderators, Sports Moderators Posts: 49,599 CMod ✭✭✭✭magicbastarder


    dunno how thick each component is, but here's a recent experience of extra wear due to a thin chainring:

    http://www.boards.ie/vbulletin/showpost.php?p=104405284&postcount=7537


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    #6
    rflynnr
    Registered Users Posts: 984 ✭✭✭rflynnr


    Thanks all. As it turns out I've already been running a 10 speed middle chainring and it has worn to a band playing. Regardless I'm going to do the same thing again as the only alternative I can envisage is to replace the entire drivetrain, including derailleurs and shifters which makes little sense for a frame which - though beloved - is now 14 years old.


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    #7
    rflynnr
    Registered Users Posts: 984 ✭✭✭rflynnr


    Plastik wrote: »
    Suboptimal bit should probably work is my guess. The only real problem I would foresee would be if the width of the spider arms changed slightly between the 9 and 10 speed systems which may mean that your current chainring bolts are either too long or too short.

    The BCD's the same - 130mm.


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    #8
    Plastik
    Registered Users Posts: 2,980 ✭✭✭Plastik


    rflynnr wrote: »
    The BCD's the same - 130mm.

    That's the spacing between the bolts from each other, not what I was referring to. If the 10s chainring has a slimmer interface than the 9s chainring around the bolt hole at the spider, then there is a possibility your bolts may be too long.


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    #9
    rflynnr
    Registered Users Posts: 984 ✭✭✭rflynnr


    Plastik wrote: »
    That's the spacing between the bolts from each other, not what I was referring to. If the 10s chainring has a slimmer interface than the 9s chainring around the bolt hole at the spider, then there is a possibility your bolts may be too long.

    Ah - I see your point and, given that the 10 speed ring is slimmer than the 9 speed, logically the bolts should be too long. Nonetheless, in practice (again it turns out I'm already running a 10 speed chain ring), there doesn't seem to be an issue.

    In further news, I am pricing buying elements of a new groupset. To my surprise I can probably get a Tiagra 4700 triple crankset, front and rear derailleur and shifters for about €185 so I may yet go that route. (I do like this bike.)


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