Bottom bracket for conversion - help really needed

Discussion in 'Singlespeed' started by cfoc, Mar 11, 2007.

  1. cfoc

    cfoc New Member

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    Hi,
    I am attempting to convert an old crappy BigW Huffy into a singlespeed commuter. the cranks were a one piece with bb and I was wondering how to determine the correct bottom bracket for this?

    the local bike store said possibly a bmx bb but did not sound keen on doing it as they were talking about removing cups or something. how do I determine the correct size bb (and if in fact I need a bmx one) and then the appropriate cranks?

    Simple stuff from a simple bloke.

    Cheers.


    I forgot to add that there appears to be no threading inside the bottom bracket housing on the frame.
     
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  2. p38lightning

    p38lightning New Member

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    You are trying to make "a silk purse out of a sow's ear". While it is possible to convert your 1 piece crank into a modern 3 piece, the cost of doing this far exceeds the value of your Huffy. Harris cycles sells a Truvative kit for $25 but this is just the unit to mount an English Bottom bracket ( about another $60+) And you'd need about a 109mm (guess) Pista spindle to get decent chain line and of course a Pista crank (probably $100+). And we haven't even gotten to the rear wheel yet!http://sheldonbrown.com/harris/opc.html is the link to Harris cycles, check out the parts and see what I'm getting at. My advice is to jam something into you rear derailler to postion it over your chosen rear sprocket, or tie off the shifter cable or something like that and call it a single speed and ride it.
     
  3. alfeng

    alfeng Well-Known Member

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    FWIW. If you go to DAN'S COMP [BMX oriented "stuff" - www.danscomp.com], you will find another source for what you are looking for (or, at least, reference in case you want to shop elsewhere).

    An adapter is made to fit a standard ENGLISH THREADED (1.37x24) bottom bracket into your "American"/ASHTABULA one-piece bottom bracket shell:



    Request their catalog ... I think there is a short explanation which presumes you know what you want vs. Sheldon Brown's copy which more poetically encourages you to update your old frame from Ashtabula-to-English. ​


    It is similar to (the same as?) the BB shell adapter that Harris Cyclery (aka Sheldon Brown) offers except the one at DAN'S COMP appears to be polished while the one at Harris appears to be anodized.​


    Converting old frames to a new use is ALWAYS a dubious enterprise, as noted, but I should say that there is something about being eccentric ...​


    BTW. If, by chance, your current crank has two, welded together chainrings, you can remove them and simply substitute a BMX crankset spider (probably, $10-to-$30 depending on where you get it and the condition ... eBay-to-an-LBS) which will then allow you to mount any standard 110BCD chainring OR you can mount a single, BMX chainring with a fixed tooth count. The latter would be the least expensive ... the former would give you a lot of versatility in tooth count. Just remember to regrease your bearings when you re-assemble your crank (you will need to take it off to change the chainrings to a "single" chainring).
     
  4. cfoc

    cfoc New Member

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    Thanks for the replies guys. I did call another bike shop and found out it was an American bb then looked up info on the web.

    I was going to go the bb conversion but alfeng's last comment about using the existing crank arms with a chainring sounds very simple (in theory anyway - especially since I didn't pay any attention when pulling the cranks/bb apart to the order of everything). I just rescued the whole crank/bb from the bin and will give it a go.

    Anyone know of an exploded diagram of one of these American bb's? I will google it but I am crap at googling effectively.

    I know it sounds like more work than it's worth but the frame is a great fit for me (only about 165cm or probably 5'5" in US measurements) and it has really long near-horizontal dropouts on it. since it will be my first ss build I don't want to spend the money on a ss-specific frame. Only ridden ss a little in Japan when I broke the gear-cable on a 'mama chari' and was too cheap/stupid to fix it.

    Cheers.
     
  5. cfoc

    cfoc New Member

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    Found the US BB here http://sheldonbrown.com/harris/opc.html
    Will normal clipless pedals fit on BMX cranks or is there a distinction in size between the one-piece cranks and 2/3 piece ones?

    Cheers.

    never mind. found the relevant info further down the same page as above.
     
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