What cranks and BB combo's to make a cheap FW?

Spinacilight
Spinacilight Posts: 1,738
edited August 2007 in Road general
Hi. I'm looking to build up a cheap fixed wheel using an old steel 531 frame. I've got spare Campag Centaur and Chorus chainsets and also the matching bottom brackets and was wondering how to get the best chainline using what I've got but without resorting to the fugly inner-ring option!

I've previously used a Shimano chainset with a Chorus bottom bracket and got a fantastic chainline but those parts are still in use and I was wondering if there is some other combinations that work. I don't mind shelling out on a Shimano bottom bracket but I really don't want to buy another chainset.

Thanks!

Comments

  • NorwegianBlue
    NorwegianBlue Posts: 484
    I don't have any experience with the chainsets you mention, but...

    You need to know the following figures:

    The offset from the centre line of your sprocket.
    The offset from the centre line of your outer ring with the standard BB.
    The axle length of your BB.

    None of these are difficult to measure with a cheap set of vernier calipers and a little thought. The first two may even be documented by the relevant manufacturers.

    Then you take the first from the second, you should end up with a positive number. Now double this. You need a new BB that is this much shorter than your original BB.

    None of it is rocket surgery.

    Usining the outer ring can be problematic with some chainsets, especially triples as setting the chainset in by so much can result in it fouling the frame or BB. I had one double, don't recall the make, that had the bosses for mounting a granny ring and these fouled. Not insurmountable as you can machine off enough material from the chainset to allow it to clear,

    Another potential problem with some frames is the lack of clearance with a big ring. My current fixer (a converted Raleigh Crit) wouldn't work with the 52T ring that I thought looked better, so I used 42T instead. Something slightly bigger would have fit but it was a 52/42 chainset so the 42 was free. I ended up with 42/16 gearing instead of the 52/19 I was planning to use.
    "Swearing, it turns out, is big and clever" - Jarvis Cocker
  • piedwagtail91
    piedwagtail91 Posts: 781
    you may be able to get good chainline easily if you use the centaur with a miche track bottom bracket. i'm planning on using this setup on a second fixie when i get all the bits together.
    the miche bb doesn't have a "fixed drive side cup" so you can offset it slightly in either direction.
    think the bb is about £15 from parkers mail order

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