help needed for bb size

sel1973
sel1973 Posts: 5
edited July 2011 in MTB workshop & tech
hi, im new to all things mtb so please be patient, the bb on my 2009 kona caldera is clicking and grinding but i dont know which replacement to get i believe the ones fitted arn't original, the original should have been fsa mega exo, the ones that are fitted i believe to be shimano i know from the spec sheet that its a 73mm bb, but one bearing shell says smbb51 (L) and the other says smbb70 (R). i dont know which to be, any help would be much appreciated, thanks Neil.

Comments

  • benpinnick
    benpinnick Posts: 4,148
    73 is probably the size. Either that or 68 (only two bb shell options). Simple test - measure the bb shell. The bit of the frame the bb fits into will be either 68 or 73mm wide. Is it a external type bb (where the axle is attached to the chainset)?
    A Flock of Birds
    + some other bikes.
  • sel1973
    sel1973 Posts: 5
    it is an external type bb and the spec sheet says its 73mm but when im searching online ive found both smbb 51 and smbb 70 listed and i seem to have one of each that why im confused.com
  • nicklouse
    nicklouse Posts: 50,675
    External BB cups then. just buy some and fit the same way as the current ones.

    see Parktools for more infos.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • sel1973
    sel1973 Posts: 5
    ARGHHHHHHH, what i need to know is why does one bearing cup say SM BB 51 AND THE OTHER SAY SM BB 70, SHOULDNT THEY BE THE SAME? The guy at my lbs says they should be the same although he mainly does road bikes, what should i be measuring, to find out what i should be buying or will any 73mm bb work?
  • nicklouse
    nicklouse Posts: 50,675
    why would they be they are not the same?

    just get some MTB external BB cups for a HT2 set up.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • cooldad
    cooldad Posts: 32,599
    External BB doesn't matter what the BB width is as they fit on the outside.
    Just find a nice cheap Deore HTII.
    I don't do smileys.

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  • benpinnick
    benpinnick Posts: 4,148
    Just means your current BB is half XT half Deore (bb70 being XT, bb51 being deore) - nothing to worry about though, theyre interchangeable.

    Just go and get yourself a new BB51 or BB70 budget depending and you'll be away.
    A Flock of Birds
    + some other bikes.
  • sel1973
    sel1973 Posts: 5
    thanks benpinnick thats exactly the info i was after, sorted ordered new bb51, thanks again, neil...

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