• This topic has 5 replies, 4 voices, and was last updated 14 years ago by sem.
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  • Speccing a square taper BB for Middleburn
  • sem
    Free Member

    I’m looking for a BB for a newly acquired frame and chainset, and have come to realise that with my limited experience, I don’t know how to make the correct selection! If you know these things, then please read on and comment.

    The set up is a Middleburn duo (42-29t), for a litespeed (68mm BB) with Mavic crossmax and a SRAM cassette and derailleur.

    I assume the width controls the chainline, and while some may be slightly adjustable (Phil Wood 2mm??) some are certainly fixed (Shimano UN54, etc).

    How do I choose the BB width? Does anyone know what will work with this setup?

    bigrich
    Full Member

    113mm.

    unfortunatley your a bit limited for bbs as shimano stopped making their excellent and almost indestructible un72.

    but seeing as the ’52 is (used to be) about 15 quid you cant really go wrong. sq taper bbs arnt subject to contamination like external jobs, and you should get at least a year out of it. if you want to spend more on a phil wood, well, thats up to you, but its a very diminished return on the increased investment.

    Stoner
    Free Member

    UN54 is a great value current model.

    Some UN72/73s available s/h or NOS on eBay or classifieds.

    113mm axle length needed for standard 48-50mm MTB chainline.

    Since you’re running a double, you could probably get away with running a shorter axle if you wanted to, but you may have trouble unless you know what you’re doing with the front mech.

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    convert
    Full Member

    Royce have got hundreds of options of length so you could tweek alittle off the 113mm standard (well about 75 from the email I got from them) but it would cost you (£115 direct I think for a titanium one). I was in the exact position you were in last week and in the end went for a Middleburn isis chainset with a SKF Isis BB that Middleburn are now importing (contrary to popular belief and what Pace, the old importers, tell you, the SKF is still in production).

    bigrich
    Full Member

    oh and in associated news, I cracked my 10 year old rs7 cranks a couple of months ago, emailed middleburn and got a free replacement crank sent in the post the next day. I’m in Oz, so thats top class service!

    sem
    Free Member

    Thanks for the comments and advice. I’ve placed an order for a UN 54, as I’ve had good experience with my other shimano BBs and when you weight the cost vs performance, they’re tough to beat.

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