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Will this chainring be ok?

Started by sirantonycartwr · · Last activity · 6 posts · 1,299 views

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01 / Original postWill this chainring be ok?sirantonycartwr · 9 May 2007 02 / This pagePosts 1–6Page 1 of 1 · chronological order 03 / Latest replyPost #6sirantonycartwr · 10 May 2007

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Original section
Cycling Equipment
Published
9 May 2007
Last activity
10 May 2007
Original author
sirantonycartwr
Posts
6
Discussion status
Public discussion
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1,299
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Topics
Front derailleursDrivetrain compatibility

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  1. Original post
    sirantonycartwr
    Archived post
    #1

    Hiya, ive currently got a Truvativ crankset 42/32/22 and a 32-11 freewheel.

    I want to buy this item:
    http://cgi.ebay.co.uk/Shimano-XT-M760-M761-48-Tooth-48t-Chainring-9-Speed_W0QQitemZ160113758570QQihZ006QQcategoryZ56193QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

    But ive been thinking that this chainring might make gear changing difficult.

    it would make my bike 48/32/22.

    the circumference of the 22t is 28.6cm with a 4.5cm dia
    the circumference of the 32 is 41.6cm with a 6.6cm dia <2.1cm step up>
    the circumference of the 42 is 54.6cm with a 8.7cm dia <2.1cm step up>
    so the front der has to step up 2.1cm, which it does ok.

    the circumference of the 22t is 28.6cm with a 4.5cm dia
    the circumference of the 32 is 41.6cm with a 6.6cm dia<2.1cm step up>
    the circumference of the 48 is 62.4cm with a 9.9cm dia<3.3cm step up>
    the front der would have to step up 3.3cm with this config, how do i know if it can do it?

    Ant...

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  2. Scotty_Dog
    Archived post
    #2
    sirantonycartwr said:

    Hiya, ive currently got a Truvativ crankset 42/32/22 and a 32-11 freewheel.

    I want to buy this item:
    cgi.ebay.co.ukShimano XT M760 M761 48 Tooth 48t Chainring 9 Speed W0QQitemZ160113758570QQihZ006QQcategoryZ56193QQs

    But ive been thinking that this chainring might make gear changing difficult.

    it would make my bike 48/32/22.

    the circumference of the 22t is 28.6cm with a 4.5cm dia
    the circumference of the 32 is 41.6cm with a 6.6cm dia <2.1cm step up>
    the circumference of the 42 is 54.6cm with a 8.7cm dia <2.1cm step up>
    so the front der has to step up 2.1cm, which it does ok.

    the circumference of the 22t is 28.6cm with a 4.5cm dia
    the circumference of the 32 is 41.6cm with a 6.6cm dia<2.1cm step up>
    the circumference of the 48 is 62.4cm with a 9.9cm dia<3.3cm step up>
    the front der would have to step up 3.3cm with this config, how do i know if it can do it?

    Ant...

    Your current front derailleur might not work with a 48 tooth chainring.

    Determine the exact model of your front derailleur, then check the manufacturer's website for the maximum number of allowable teeth for the largest gear. For example, a Shimano XT FD-M760 shows 44T as the max, whereas a FD-M761-3 allows 48T.

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  3. sirantonycartwr
    Archived post
    #3

    http://www.srsuntour-cycling.com/SID=si806f1f78dcda143901f0a1f032b876/index.php?screen=sh.detail&tnid=640

    Looks like its not compatible.
    Thanks, Ant...

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  4. alfeng
    Archived post
    #4
    sirantonycartwr said:

    srsuntour-cycling.comindex.php

    Looks like its not compatible.

    Actually, the front derailleur cage's outer plate is capable of handling a wider range than Shimano's apparent specs ...

    FWIW. I've got an 8-speed XT front derailleur shifting a 52/39 double (ROAD crank) -- the outer plate is almost (if not actually) the same shape as the outer plate on a Shimano ROAD front derailleur designed for a double crank [sorry about the poor quality of the attached picture].

    No problems shifting, but I'm using Campagnolo ERGO shifters!

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  5. Scotty_Dog
    Archived post
    #5
    sirantonycartwr said:

    srsuntour-cycling.comindex.php

    Looks like its not compatible.
    Thanks, Ant...

    You could always buy a new front derailleur, such as this:
    cambriabike.comshopexd.asp

    Report
  6. sirantonycartwr
    Archived post
    #6

    I think ill buy a chainring, try it and see what happens.
    Ant...

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