• Is there something I can measure on an old pair of cranks to work out whether they're JIS or ISO?

    They're an obscure White Industries by Sugino triple crankset that I can't find much information about on Sheldon, velobase, etc.

  • I think the flat section of the taper is shorter on ISO BBs, but I can’t remember the details. There’s a link to post by @mdcc_tester that myself and others have re-posted up thread that has a useful diagram which I think would help. Will update this post if I find it.

    Edit: https://www.lfgss.com/comments/8756147/

    Not sure what diagram I was remembering though. Plus I think the cranks would be the harder element to ID. Sorry, no help whatsoever!

  • Sounds like it doesn't matter according to that. I had been led to believe different from my googling thus far.

  • I have an ISO chainset on my track bike, which I’ve been using with a JIS bb for a while now. No issues whatsoever and the chainline is spot on according to my callipers. As long as you can avoid bottoming out an ISO bb spindle on JIS cranks, the only problem you should encounter is just finding the right spindle length.

  • Thinking about it for a while I realised WI make/made square taper bottom brackets. And those are JIS. Assuming that they would seek compatibility with their own BBS, I'm going to assume that's the taper.

    Now... To work out the spindle length........

  • ISO or JIS

    As long as you make sure the taper isn't too long or short, it doesn't matter:

    ISO BB is about ~2mm shorter than stated with a JIS crank

  • hi, new to the forum although been riding a long time. I have been riding this Langster since Feb this year and it's time to replace the BB.

    I'm struggling to remove it at the moment but using a tape measure it appears to be 68/103

    Can anyone confirm if this is correct and if so any recommended BB?

    Also if anyone knows which year model the Langster is that would be good too.


  • No one? I applied a bit of GT85 yesterday (run out of WD40) and left it overnight. That and my good friend Mr Leverage who helped thanks to using a socket wrench extender and it's out.

    BB is an RPM BB-7420 model. It's too rusty to see the size marked on it but my tape measure confirms BB shell is 68mm and axle width is 103 mm

  • I need advice.

    I have a 54cm Pre-Cursa, 170mm Andel fluted cranks, Un55 105mm BB and rear Quando hub (Varno build).

    Will it give me a useable chainline (OR, how do I find out how to calculate it before fitting it all and hoping for the best)?

    First bike build for 10 years so I have forgotten everything.

  • Are the cranks these ones? If so, it looks like you need a 110mm BB to get a chainline of 42mm (105mm will be 2.5mm out).

  • Balls. They are, yes.

    Is chainline being out by 2.5mm gonna be a big problem?

  • Probably fine, but a un55 in 110mm isn't going to set you back much so personally I'd get it right and not have to worry about bursting in to flames or being beset by a plague of skidding locusts (or whatever happens when chainline is out by too much).

  • Just double checked, it’s 107mm. At 1.5mm I’m gonna risk it! 😮
    Cheers for your help!

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Transmission database - for all your crank / bb / bottom bracket questions

Posted by Avatar for kowalski @kowalski