JIS / ISO BB - Does it matter?

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  • Hi

    Hoping someone can clarify this for me.

    Firstly - I've used the search and can't find a definitive answer.

    Secondly - I've also looked at the transmission database and am still no wiser.

    I have a set of vintage Sugino mighty track cranks - they look like this:

    I need to get right chainline to run with Miche Primato hubs which I presume is 42mm.

    So what BB do I need? 68mm shell in frame but need to check the threading as frame came from france and is unbranded.

    Transmission d'base indicates someone is running a Shimano UN54 BB with these.

    The cranks are definitely ISO. Is the Shimano BB ISO or JIS - and more importantly does it matter?

    Frame came with a Stronglite BB but it is fairly obvious even putting the cranks on by hand that the taper is not compatible.

    Thanks in advance.

  • it does matter as the tapered axle on jis and iso are different, so basically using the wrong bottom bracket the cranks won't sit properly on the square taper if they don't match.

  • Short answer is yes, it does matter.

    Shimano is JIS. 68mm shell is almost always english threading.

    Shimano UN 54 is fine, someone more knowlwdable than me should be able to advise on axle length. I think 107 mm is the shortest UN 54 comes in which may be too long

  • Thanks but aaaargh!

    You've just said that it does matter whether JIS or ISO.

    I've said the cranks are ISO. You then went on to say UN54 should be fine but are JIS- thus immediately contradicting yourself!

    Sorry but this is proper doing my head in!

  • http://www.sheldonbrown.com/bbtaper.html­ will answer your questions.

  • No he won't. Read my OP and come back with the answer. Which BB do I need and what length spindle?

  • It does matter. Get the right bottom bracket.

  • Yeah thanks - big help Max.

    It does matter. Get the right bottom bracket.

  • only make a difference to the chainline (mostly) if you've read Sheldon Browns explanation then there would be no need for this thread.

  • where's my angry mummy thing... 2 secs...

  • and it effects the way the crank wears through

  • shimano is definitely JIS which is not what you want,
    some common brands of ISO bb are miche, campagnolo and some sugino.

    *do not read this if you do not want to be confused - *
    it is possible to interchange iso and jis, sheldon brown says it is perfectly fine:

    If you install an ISO crank on a J.I.S. spindle, it will sit about 4.5 mm farther out than it would on an ISO spindle of the same length. Confersely, if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length.
    Theoretically, ISO cranks should only be used on ISO spindles, and J.I.S. cranks only on J.I.S. spindles.
    In practice, you can very often get away with mixing these sizes

  • Yeah? So you're so clued up - what do i need? Not being chippy but if you can work it out (and provide reasons for your answers) :

    a) I'd be very grateful

    b) So would a lot of other people.

    It's very easy to point to the Sheldon stats and believe me I've fitted many (new) bottom brackets.

    Not one of you has yet come up with anything but look at Sheldon Brown. I'll even offer a cash prize for the 1st correct answer - so come on...

    EDIT - sorry - aimed at non specific posts not all.

  • I think Cohen gave you your answer. If you've fitted many botom brackets before, then you should know the decent ones by now...

  • The cranks are definitely ISO.

    some common brands of ISO bb are miche, campagnolo and some sugino.

    can i have my prize now?

    (what pip says about mixing iso/jis causing wear is right but this fixxie fad will long be over before that happens)

  • Specific answers please.

  • in the transmission database i just found this:

    Sugino Super Mighty + Sugino 109 + Dura Ace + Phil Wood = Dayno

    so it appears you need a 109mm ISO bb (its sugino),
    the sugino 75 bb is 109mm and just what you need, but costs £££
    if you want a cheaper option go with miche 107mm bb, it is adjustble a couple of mm each way so you should be absolutely fine

  • i have just overcome a similar problem so understand your grief entirely :-)

  • At last - thanks.

    Cohen - you can claim your cash prize (provided cahinline is spot on!)

    The rest of you - meh....

  • another top tip is using a thinner or thicker sprocket, eg. dura-ace sprockets sit out one whole millimeter further than phil wood sprockets! truly gripping stuff..

  • Why are people on the internet soo rude.

    YOu are going to have to do a bit of work yourself.

    Find a spec sheet for the cranks if it exists ... it will tell you the chainline with particular spindle type and length. e.g. I know that FSA vero cranks double crankswill have a 43.5 mm chaninline with a 110.5mm JIS BB, because I downloaded the FSA catalog.

    If it doesn't exist ...

    Get an old(ish) BB that is symmetrical and is either ISO/JIS fit it and stick the cranks on, measure the chain line and note the length of spindle. if the spindle is symmetrical it is relatively trivial to calculate the length of the spindle for that particular interface type.

    Then once you know this you can add or subject 4.5mm whether you buy ISO or JIS like it says on the link I posted previously and buy the right BB length.

    EDIT: looks like the answer has been found.

  • tbh lucas i agree with you, i little bit of htfu is needed goodhead!

  • No offense Lucas but yeah - in a way I agree with you.

    The weird thing is that the internet allows you to communicate with people and ask questions about things that may have frustrated you for a while.

    This is what I did.

    I asked a very specific question, hoping for a very specific answer.

    I did not abuse anyone but merely responded to the many responses to me saying 'look on Sheldon Brown...'.

    I'd already done that. I'm not an expert mechanic, nor do I have access to try out different BB's hoping that I'd got my calcs correct.

    I'm sure you'd agree that the information on the internet is sometimes conflicting. So oddly I asked a specific question in a forum dedicated to bikes, hoping for a specific answer - did I do wrong?

    Thanks to all who either tried or did help. Sorry if I seemed rude - it was not intentional - more from frustration.

    p.s - can you please find me a spec catalogue for 70's sugino mighty cranks?

  • Don't worry about it.

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JIS / ISO BB - Does it matter?

Posted by Avatar for goodhead @goodhead