choosing crankset and bottom bracket for surly 1x1/rohloff- Mtbr.com
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  1. #1
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    choosing crankset and bottom bracket for surly 1x1/rohloff

    I'm building my first bike and using a Surly 1x1 and rohloff in the rear. I'm confused about how to pick a crankset and bottom bracket to give me the proper 54mm chain line. I've read that some people using the outer chainring on multi ring cranks but since I'm making this bike from the ground up I'd like it to be clean. Someone told me I just need a long enough bottom bracket for the crankset I pick, but I don't have a reference to figure out how to calculate this stuff with. Can someone tell me a crankset and bottom bracket combination that will work on a Surly 1x1 (73mm bb) to provide a 54mm chain line, or else just tell me total chainline of their combo and the length of their BB / model crank so I can figure out how to calculate a combo to give me 54? Is it just half of the bottom bracket length that I want, or half of that plus some portion of the crankset, or what?

    Thanks

  2. #2
    Crazy C
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    vermillion1,
    Congrats on your new rig and especially for your new rohloff!! Sorry you've been waiting a week for a response and it seems you joined up just to post this message. Don't dispair...this doesn't happen too often from my experience.

    I'm no expert on q-factor or the 54mm chainline standard but I will tell you that if you go with an ISIS or shimano BB the 113 should get you there. RaceFace BBs are adjustable which makes it easy to achieve perfect chainline. The newer 2piece crank designs are not as versatile as far as I know, but you can also play around with running the chainring in the mid or outer position and add/remove chainring spacers.

    On my rig, I was using an ISIS Raceface crankset and BB and ran the chainring on the inside with a bashguard on the outside. Recently I ditched the bashguard and switched to a Truvativ BB. All I had to do was switch the ring to the outside, alignment was no issue.
    Good luck with your build...hope this helps (in time).
    Crazy C

  3. #3
    Obi
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    Wink ooops, missed this post, my bad...

    Ditto that, sorry, I'm usually one to give an open "Welcome, and...", but was out doing trail work this weekend.

    So, yeah, the ISIS, or any current crankset will allow that chainline, as all/most are set-up to have the middle ring spaced right around 50mm, so when you put the single ring, on the outermost point, it should give 52-54 mm. If you're still unclear, call the Surly Boys, or shoot a reply post here.

    BTW: Optimal chainline is measured from the centerpoint of the seat tube, (usually there's a bottle boss there to use as a start), to the center of your middle chainring, or in this case, as I stated above.



    BTW: "The newer 2piece crank designs are not as versatile as far as I know, but you can also play around with running the chainring in the mid or outer position and add/remove chainring spacers."

    Partly correct, yes, and no... you can pick up some shims, like with a BMX bb, and play a little, but realistically, nothing more than 1mm total added to a 73mm bb.
    Obi..

  4. #4
    Obi
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    Wink

    Oh yeah, you know that all this is blasphemy.

    Post a pic in the Post Yer Surly thread when it's done.

  5. #5
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    I would go with a good old square taper UN73 BB and just get the right length to give the perfect chainline. One of the best BBs ever made and square taper is still good enough for most of the pro peleton. I use a Campag Centaur chainset (double) with a single 39 tooth (20 rear) chainring. It looks beautifully clean and gives lots of teeth to spread the load. And every bike needs at least one piece of Campag on it...!




  6. #6
    Duckin' Fonuts.
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    Campy cranks and Shimano square taber BB's are not really compatible. The Campy tapers are a steeper angle and a Campy crank will pull too far on to a JIS (Shimano) square BB. A Shimano or Sugino crank will also not work on a Campy BB. The cranks do not press far enough onto the spindle. I like Race Face square taper cranks, They are ebay only or old stock at some shops but, still worth it. They work on Shimano JIS, I think that is Japanese Industrial Standard, BBs.

  7. #7
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    Hmmm, it's a fair point but really a bit of an old chestnut - officially there is a tiny difference in the taper angle of Campag/Shimano (BB) set-ups but it an often used combination with zero problems in practise.

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