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  1. #1
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    Dura Ace FC-7402: which BB?

    I just bought an 80s Faggin frameset (pics at http://bikeforums.net/showthread.php?t=363421) and am going to put a new Shimano 10 speed drivetrain on it. I have a set of Dura Ace FC-7402 cranks, which are 9 speed, but Sheldon Brown's site says there's no difference in the spiders b/w 9 and 10 speed, so if I get 10 speed chainrings I should be good to go.

    I found on the internet somewhere that this crankset takes a 113mmx70mm Italian BB. Will a BB w/these dimensions give me a good chainline for a Shimano 10 speed cassette? I know that Shimano's BB-UN54 comes Italian threaded in a 113mmx70mm square taper, but I don't know how it stacks up to other BBs. Have other people had good experiences w/the UN54? If not, any other suggestions? Thanks.

  2. #2
    vasracer
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    You mean the frame takes a 113x70mm Italian Bottom bracket. Usually 113mm bottom brackets are for triple cranksets. If you have a triple crankset then your good but if you have a double the crank might sit out just a bit too far and you run the risk of derailing you chain.

    If you have a double chainring crank try finding a 109mm x 70mm Italian bottom bracket. This will bring your chainline closer to your frame. This will eliminate extreme chainline angles and reduce the risk of derailment.

  3. #3
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    Quote Originally Posted by vasracer View Post
    You mean the frame takes a 113x70mm Italian Bottom bracket. Usually 113mm bottom brackets are for triple cranksets. If you have a triple crankset then your good but if you have a double the crank might sit out just a bit too far and you run the risk of derailing you chain.

    If you have a double chainring crank try finding a 109mm x 70mm Italian bottom bracket. This will bring your chainline closer to your frame. This will eliminate extreme chainline angles and reduce the risk of derailment.
    Thanks for the reply. I found the measurements for the BB here:
    http://www.bikepro.com/products/bott...omptable.shtml

    I assumed this meant that the crankset was only compatible with this size BB. If this is not the case, and spindle length will vary w/frame, what's the point of that compatibility table?

    Also, the crank is a double.

  4. #4
    cab horn
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    Quote Originally Posted by digitalbicycle View Post
    If this is not the case, and spindle length will vary w/frame,
    Uh. Why would this be true. Spindle length 'x' gives chainline 'y'. That doesn't change on any bike. Unless the crankset hits the chainstay and you have to get a longer bb.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  5. #5
    A little North of Hell
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    7402

    7402 should be 8spd

    112-113 bb

    http://www.sheldonbrown.com/bbsize.html#dura
    [SIGPIC][/SIGPIC]
    XXXI

  6. #6
    Senior Member
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    Quote Originally Posted by Soil_Sampler View Post
    7402 should be 8spd

    112-113 bb

    http://www.sheldonbrown.com/bbsize.html#dura
    Damn, I don't know where I got the idea that 7400 was 9 speed. Are there going to be any compatibility problems using the 7402 crankset with a newer 10 speed drivetrain, provided I buy new chainrings?

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