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  1. #1
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    Need new bottom bracket - HELP

    Hi

    Just taken BB off my road bike, on the inside it says - BB -UN71 and on the side it says BC 1.13 68, now then I've done a search for BB and I can't find a UN71 and when I look at other BB (UN54) I can't find on thats BC 1.13 68, can someone advice me on what to do

    Thanks

  2. #2
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    ok... the 68 is the bb shell size... the bc means that is british thread... the 1.13? probably u got something wrong in there and the dot is not there... I mean probably is a stain or something 113 is the lenght of the axle.

    Swap it by a UN5x BC 113 68 unit.

    Thanks.

  3. #3
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    UN71: higher quality (ultegra/XT)
    68: width of bottom bracket shell
    113mm: lenth of spindle.
    Any JIS pattern square taper BB unit with 68/113 size will be suitable as a replacement. The most common are shimano units and they are quite good enough. You can use any of the UN7x or UN5x series. The 7x are a bit lighter in weight.

  4. #4
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    Thanks for the replies, it definitely says 1.37

  5. #5
    Senior Member MudPie's Avatar
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    Quote Originally Posted by DaveM View Post
    Hi

    Just taken BB off my road bike, on the inside it says - BB -UN71 and on the side it says BC 1.13 68, now then I've done a search for BB and I can't find a UN71 and when I look at other BB (UN54) I can't find on thats BC 1.13 68, can someone advice me on what to do

    Thanks

    "UN71" is the Shimano brand model number.
    "68" is the width of your bottom bracket shell (68mm). The other common width is 73mm.
    "1.13" is probably the length of the bottom bracket spindle. It's usually expressed in mm, so I'd be expecting it to read "113". However, you can always measure the length with a ruler to verify.

    Basically, if you match the width (68) and length (113), and crank arm interface (like square taper), then any brand of bottom bracket will work. 68 x 113 is a very common bottom bracket.

  6. #6
    Senior Member MudPie's Avatar
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    Quote Originally Posted by DaveM View Post
    Thanks for the replies, it definitely says 1.37
    "1.37" refers to the diam of the bottom threading. The threading is actually 1.37 diameter x 24 threads per inch, the most common bottom bracket threading.

  7. #7
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    Quote Originally Posted by DaveM View Post
    Thanks for the replies, it definitely says 1.37
    1.37 is related to the cups thread... in this case is english.

    Grab a ruler and measure the lenght of the axle thats the other thing u might need because untill now u havent posted it.

    Wonder if you have a metric caliper or a metric ruler.

    Thanks.

  8. #8
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    Just measured the axle and it looks like its 107mm

  9. #9
    Senior Member MudPie's Avatar
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    Quote Originally Posted by DaveM View Post
    Just measured the axle and it looks like its 107mm
    Just to clarify, your original post said "BC 1.13"?

    Did you mean to say "BC 1.37"?

  10. #10
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    Well just been on Sheldons web site ( why didn't I do this in the first place...der) and for a 105-SC 1056 double its 107mm mine is a 105 FC 1056. so I presume they will be the same

  11. #11
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    I,m really sorry mudpie I did mean BC 1.37

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