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  • BOTTOM bracket measurements?

     11redrex updated 12 years ago 3 Members · 7 Posts
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  • 11redrex

    14 May 2009 at 3:10 pm

    Going to need to replace my BB, chainset and cranks soon and I don’t know what I need to measure for the BB.

    Help ?

  • Steve Kish

    14 May 2009 at 3:15 pm

    Cup size will either be:-

    1.37 x 24tpi. Most common and has a left-hand thread on the spider side


    36mm x 1mm (Italian), quite rare. Easily seen as the spider side is standard right-hand thread and is probably done up by Arnold Schwarzenegger, as these come undone.

    Then just the overall length of the spindle, about 111 or 113mm for a triple.

  • 11redrex

    14 May 2009 at 3:29 pm

    cup = shell ?

  • tomlevell

    14 May 2009 at 3:43 pm

    Assuming MTB and a normal BB not an external bearing type.

    BB Shell width. (the bit of the frame the BB screws into)

    68mm or 72mm.

    Measure the width with calipers/ruler/string

    BB spindle width – The bits the cranks attach to

    Remove Cranks and again with calipers measure between the two ends.

    Probably 113mm but maybe 118mm.

    The width may be stamped on the body of the BB after you remove it but probably isn’t.

    Or could be something random.

    Oh and Steve not nearly anal enough you missed loads out.


  • 11redrex

    14 May 2009 at 10:45 pm

    ok so it’s just those two measurements then ? Been looking at various bb’s and some of them have all sorts of numbers stamped on them.

    I’ll whip mine out tomorrow and see what I can see. The bloody crank came loose on Tuesday, got it home (Lidl underseat toolkits don’t have a 14mm socket in) and tightened the bolt, came loose again Wednesday, tightened it and threadlocked the basteward, and it came loose again today.

    When I was fiddling I noticed the middle and large chain rings are both bent, and the plastic guard is cracked, so I reckon I wolloped something (note to self : not 14, must stop riding like I am)

    Also the new pedals I put on there on Monday have chewed into the cranks, which seem to be made of some sort of marshmallow and coal alloy.

    Might be time for a wanted post, or a different bike. I could have bought a decent one and paid for it monthly for less than I’m spending on this bloody thing !

  • Steve Kish

    14 May 2009 at 10:46 pm

    Cup = the thing that screws into the shell. 😀

  • 11redrex

    15 May 2009 at 1:10 pm


    So, got it all out, there seems to be something missing. All the ones I’ve seen for sale have a tube joining the two end cups. , Mines just a cup at each end, with a race inside for the bearings, and the axle/spindle/shaft/thing (delete as appropriate) poking out both ends.

    He-e-e-ennyway Got it all off , cleaned and greased everything, put it all back together, and it seems to be holding up.

    Crank side cup (they’re left hand thread don’t ya know 😉 screwed in with bearing in place, spindle poked through, left hand cup and bearings on, round thing screwed on, cranks on and bolted down, all seems good.

    Measured the frame width where the cups screw in as 68mm and the spindle length as 118, so I arseume that’s the sizes I should be looking for when searching for a new one ?

    Shimano UN54 any good, they seem to be cheap and have good reviews on chainreaction…??

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