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Bottom bracket and crank size question

inceince Posts: 289
edited June 2009 in The workshop
Hi guys, I have got hold of one of the Ribble TT frames and I intend to build it into a single speed. I am gathering the parts I need atm and I have started to look for bottom brackets and cranks.

I have never built up a bike from this point before and I could do with some advice about how to work out what size bracket I need. I have taken the inside span of the threads in the bottom shell of around 67mm, how do I now go about working out what lenght axle I need?

I have been looking at the Sugino cranks and bb on ebay, the seller recomends the use of a 103mm bb which seems short. Also is british standard thread a standard type?

Last of all is the Sugino stuff any good?

thanks in advance :)

Mark

Posts

  • nicklousenicklouse Posts: 81,520 Lives Here
    it will be 68mm bb width.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • WooliferkinsWooliferkins Posts: 2,060
    As always Sheldon Brown has the answers. You have a 68mm shell which is English and is pretty much standard. The english BB threading standard gives you a BB with one left and one right hand thread so the rotation of the cranks can not unwind the cups.
    Neil
    Help I'm Being Oppressed
  • inceince Posts: 289
    Thanks for the info, the Sheldon site has all the info I think I will need. From what I have just read (very quick glance) I think I may have just been confusing myself due to lack on knowledge. :shock:

    Time to do some reading.
  • nielsamdnielsamd Posts: 174
    Just saw this thread today.
    How is the build working out?
    Would be interesting to see a photo when its done.

    Just my .02 worth based on what I read above: I think some confusion may arise because a lot of `fixed gear/single-speed' frames advice will assume a rear track hub dropout spacing of 120mm.
    I more than suspect your Ribble TT has standard road 135mm.
    So, not just for chainline issues, the 103mm BB axle you mentioned perhaps should be a bit further out..say 108mm+ ... so that a large chainring can clear your more `splayed' chainstay.

    The 68mm shell size is pretty much the standard for most (Brit) frames.
  • inceince Posts: 289
    Thanks Nielsamd.

    Yep you are right the rear drop out is the larger 135mm, I measured the internal gap as 130 (but I did do this quick with an old tap measure).

    I have spoken to the LBS and got same advice about the axle width, he also recomended a 108mm axle.

    All the bits are coming together, still need to sorce some wheels bb and crank. Getting the parts on an as and when so may still be some time. :D
  • System_1System_1 Posts: 513
    Dropout width really has very little to do with chainline though. It's the hub shell and position of sprocket that decides chainline not dropout spacing. Goldtech hubs for instance have a 45mm chainline on all 4 of their hub sizes, the only difference between them is the axle length.

    I'd decide on what hub you are using before you go trying to guess chainline. They vary between manufactuers with anything between 42mm and 47 being fairly common.
  • whyamiherewhyamihere Posts: 7,333
    02062009025y.jpg

    Mine. Not ridden yet due to injury.

    68mm English BB, 130mm spaced dropouts, BB axle depends on the cranks.
  • inceince Posts: 289
    Well I finished it today, well almost...

    http://picasaweb.google.co.uk/lh/photo/ ... directlink

    .... still need to set it up and do a few test rides. I also have to sort out what colour bar tape to go for. :P
  • cjcpcjcp Posts: 13,345
    Ince - which forks have you fitted? Looks nice.
    FCN 2-4.

    "What happens when the hammer goes down, kids?"
    "It stays down, Daddy."
    "Exactly."
  • inceince Posts: 289
    Thanks Cjcp

    Set of felt carbon forks I picked up on evilbay. Not too sure on the spec with out looking.

    Short test ride was shown up that i will need to invest in a better seat and that fixed gear is a whole new experiance. :P
  • inceince Posts: 289
    The forks are Felt CB, that is all the info I have. More a case of right price at the right time than choice. :D
  • cjcpcjcp Posts: 13,345
    Thanks, Ince.

    They suit the bike IMO. Even better if at the right price. :)
    FCN 2-4.

    "What happens when the hammer goes down, kids?"
    "It stays down, Daddy."
    "Exactly."
  • inceince Posts: 289
    first test ride today of any distance (halfway to work and back). All seems good, got a 50cm frame the same as the my GT but the Ribble feels shorter. Will have to get the old tape measure out. :?

    I went for a 107mm stronglight bb once I bought a 46t stronglight crank and a set of single speed wheels with a 42mm chain line. Once I had the wheels it became straight forward working out what bb to get and answering my original question.

    The sheldon site had all the info I needed, thanks again for pointing me in that direction.
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