Bottom Bracket Query.

markem
markem Posts: 29
edited August 2009 in MTB general
Probably a dumb ass question but i'm just about to buy a bottom bracket and i know the 68mm - 73mm shell size measurement but what does the 113 or 118mm measurement relate to as i don't know which size i need.
I've just bought a NS Bitch with a 73mm shell and the crank is a Truvativ Hussefelt if that helps, but I just wanted to know what what the deciding factor is in spindle length.

Comments

  • Danlube
    Danlube Posts: 454
    It's the axle length.
    Kona Tanuki Deluxe
  • markem
    markem Posts: 29
    I know it's the axle length but what does the length relate to. Why would i need a 113mm over a 118mm length or vice versa.
  • supertwisted
    supertwisted Posts: 565
    It relates to your chainline. The spindle legth will affect the offset of the chain rings from centreline of the frame.

    You'll need to work out what offset you need to work with the drive chain you intend to use.

    Don't ask me how though.
    Less internal organs, same supertwisted great taste.
  • markem
    markem Posts: 29
    Well i guess i cannot make the measurements as i don't have wheels yet due to my building a bike but was thinking if i bought a 113mm length i can always use spacers to bring the crank/chainring out, where as if i buy a 118mm i cannot decrease, does this make sense.
  • supersonic
    supersonic Posts: 82,708
    What crank will you be using? It depends on the crank.

    If it is one with external BB, it comes with the axle and you simply use the spacers.

    Which model Husslefelt?
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  • markem
    markem Posts: 29
    I'm using a Truvativ Hussefelt isis drive for now and replacing a FSA Platinum BB (68mm) with a FSA Platinum (73mm) but it's just the 113mm or 118mm thing i'm trying to sort out.
    Not sure what you mean by what model, it's the same as this one http://www.uni-sport.com.pl/sklep/image ... tcrank.jpg isis drive.
    The only numbers on the arms were HI4GAG with 170 underneath that, if they identify the model.
  • nicklouse
    nicklouse Posts: 50,675
    113mm should give you the front chain line you want.

    you dont need your wheels to work out your front chain line.

    Truvative have the info on what chain line each axle length cives with all there cranks on the manual/fitting info that should come with the bb and cranks. and is downloadable from srams webby.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
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  • markem
    markem Posts: 29
    Thanks, more clear now.

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