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Thread: Changing Crank

  1. #1
    Duathlete Flynn's Avatar
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    Changing Crank

    Right now I am riding a 2004 Specialized Allez Elite Triple road bike. I never use my 3rd ring and am now looking to change to a double. Is this a very involved process or is it as simple as switching one for the other? I am using Shimano 105 components so do I need to buy a Shimano 105 double crank? Thank you in advance for your help.
    “Life is like riding a bicycle. To keep your balance you must keep moving.” -Albert Einstein

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    Senior Member sydney's Avatar
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    Quote Originally Posted by Flynn
    Right now I am riding a 2004 Specialized Allez Elite Triple road bike. I never use my 3rd ring and am now looking to change to a double. Is this a very involved process or is it as simple as switching one for the other? I am using Shimano 105 components so do I need to buy a Shimano 105 double crank? Thank you in advance for your help.
    Ya don't have to buy a shimano double 105 crank, but you will have to buy the correct BB for the crank you choose. The 105 triple uses a 118 octalinkspindle and the double uses a 109.5

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    Duathlete Flynn's Avatar
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    Quote Originally Posted by sydney
    Ya don't have to buy a shimano double 105 crank, but you will have to buy the correct BB for the crank you choose. The 105 triple uses a 118 octalinkspindle and the double uses a 109.5
    Thanks for the info!
    “Life is like riding a bicycle. To keep your balance you must keep moving.” -Albert Einstein

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    Gone, but not forgotten Sheldon Brown's Avatar
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    Quote Originally Posted by sydney
    Ya don't have to buy a shimano double 105 crank, but you will have to buy the correct BB for the crank you choose. The 105 triple uses a 118 octalinkspindle and the double uses a 109.5
    That's correct. However, there's no need to buy a new crank, you can just remove the small chainring and its bolts and installthe shorter bottom bracket. It would work with the original bottom bracket too, but the chainline will be better with the 109 mm BB.

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    Duathlete Flynn's Avatar
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    Quote Originally Posted by Sheldon Brown
    That's correct. However, there's no need to buy a new crank, you can just remove the small chainring and its bolts and installthe shorter bottom bracket. It would work with the original bottom bracket too, but the chainline will be better with the 109 mm BB.

    Sheldon "Chainline" Brown

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    However, aren't the chain rings in doubles different sizes than those on triples? I am mostly concerned about the available gear ratio on climbs. Though I want to go to a double, I do not want to torture myself with very difficult gear ratios.
    “Life is like riding a bicycle. To keep your balance you must keep moving.” -Albert Einstein

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    Senior Member Surferbruce's Avatar
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    my wife rides a triple minus the inner ring. often triples will have a 42 tooth middle ring and doubles a 39 tooth. i swapped my wifes 42 for a 38(smallest you can go on your cranks)....
    ....is it me or does that last sentence sound disturbing?

    love it when sir sheldon takes time to reply. bravo!

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    JOCP Senior Advisor
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    So all needed is to remove a chain ring? And maybe a new BB? How much would a new BB run? Would it work right?

    Elvish

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    Gone, but not forgotten Sheldon Brown's Avatar
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    Quote Originally Posted by Elvish Legion
    So all needed is to remove a chain ring? And maybe a new BB? How much would a new BB run? Would it work right?
    See: http://sheldonbrown.com/harris/botto...s.html#shimano

    The 105 version is $43.95, Ultegra is $55.95. Either would work, but I think the Ultegra is a wee bit lighter.

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  9. #9
    JOCP Senior Advisor
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    Quote Originally Posted by Sheldon Brown
    See: http://sheldonbrown.com/harris/botto...s.html#shimano

    The 105 version is $43.95, Ultegra is $55.95. Either would work, but I think the Ultegra is a wee bit lighter.

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    Score for $43.95 I could have a fake double

  10. #10
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    Just making sure I have what I need.

    New BB, double? Can be picked up at LBS?
    Adjust Shifter lever so it doesn't try to skip?

  11. #11
    Senior Member capwater's Avatar
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    Quote Originally Posted by Elvish Legion
    Just making sure I have what I need.

    New BB, double? Can be picked up at LBS?
    Adjust Shifter lever so it doesn't try to skip?
    Cheapest: Take off the granny ring and adjust limit screw on front derailler.
    Middle: Take off the granny ring, put in a 109.5 BB and adjust limit screw on FD.
    Ideal: Swapout for double cranks, install new BB and adjust limit screw.
    Ultimate: Ideal plus short cage rear derailler and shorten chain.

    On either option involving keeping your old crank you can always swap out the 42 ring for a 39. Probably about $25 mail order. Everything is fairly easy to do although you will need a BB socket and a crank puller.

  12. #12
    Senior Member sydney's Avatar
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    Quote Originally Posted by capwater
    Cheapest: Take off the granny ring and adjust limit screw on front derailler.
    Middle: Take off the granny ring, put in a 109.5 BB and adjust limit screw on FD.
    Ideal: Swapout for double cranks, install new BB and adjust limit screw.
    Ultimate: Ideal plus short cage rear derailler and shorten chain.
    In the cheapest case the chainline will blow. In the other two there is more to it than 'adjusting the limit screw'. The derailer has to be readjusted starting with the shifter in the smallest ring opsition and both limits will need adjusting. Best to start ar the beginning as per www.parktool.com repair section. Depending on how the chain was sized to begin with the chain length may be ok,but it would not hurt to check it.

  13. #13
    Senior Member sydney's Avatar
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    Quote Originally Posted by Elvish Legion
    Just making sure I have what I need.

    New BB, double? Can be picked up at LBS?
    Adjust Shifter lever so it doesn't try to skip?
    You adjust the derailer.See post #12.

  14. #14
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    I think I'll see how much LBS wants for a double crank and new BB, seems pretty simple, and they will adjust anything that needs to be with out me worring about doing it right. So I will price 'Ideal' set up, LBS usally cuts me a good deal, esp since they can resell the BB and crank (brand new bike one comes in triple)

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