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  1. #1
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    New Chainwheel or Cranks?

    In building a fixed gear from an old BCA frame, I would like to keep the cost as low as possible on this beginning bike. The stock cranks look in good shape, and I have no desire to pay for new crank arms and a new bottom bracket if all I need is a chainring. I have never done this before, so here are my questions . . .

    Is it as simple as buying a chainring in the size I want, meaning, are crankarms universal with fixed gear chainwheels?

    In looking at chainwheels it has things such as "Works with 110 or 130 BCD", what does this mean?

    How can I go about finding the right size (Meaning what do I measure, etc.)?

    Are the bolts attaching the crank arm to the chainring the ones I will use for the new one, or will the new one come with bolts?

    If you recomend new cranks and bottom bracket, what combo do you specifically recommend for a cheap price?

    And please, I'm learning, and part of learning is figuring out WHERE to look for these specific answers on the internet (Which I did with no luck). So be nice please.

  2. #2
    snupontgeam
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    I'll give it a go. The "110 and 130 BCD" is the spacing of the crank spider bolt hole locations where the chainring attach. the 130 is for the bigger (2?) rings, and 110 for the smaller. So you'll want to get a new chainring with 130 BCD. The exiting chainring bolts may be too long to work with just one ring (if they are currently attaching two) It's possible to put washers on the other side to space them out, but probably better just to buy new ones (the chainring will not come with them).

  3. #3
    IRL Banhammer idiq's Avatar
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    Measure from the center of one bolt on the spider directly to the center of the next bolt on the spider. That will tell you if it's 110 or 130 (metric).

    Once you've figured that out and are getting a new ring, since they're road cranks you'll probably need to get single speed bolts (as patrick points out) and a new BB if your chainline is off... do a forum search on getting / setting the right chainline and selecting a BB size.
    saddle sores bike club | prepare to be rode

  4. #4
    cab horn
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    Quote Originally Posted by imoprefontaine View Post
    In building a fixed gear from an old BCA frame, I would like to keep the cost as low as possible on this beginning bike. The stock cranks look in good shape, and I have no desire to pay for new crank arms and a new bottom bracket if all I need is a chainring. I have never done this before, so here are my questions . . .

    Is it as simple as buying a chainring in the size I want, meaning, are crankarms universal with fixed gear chainwheels?

    In looking at chainwheels it has things such as "Works with 110 or 130 BCD", what does this mean?

    How can I go about finding the right size (Meaning what do I measure, etc.)?

    Are the bolts attaching the crank arm to the chainring the ones I will use for the new one, or will the new one come with bolts?

    If you recomend new cranks and bottom bracket, what combo do you specifically recommend for a cheap price?

    And please, I'm learning, and part of learning is figuring out WHERE to look for these specific answers on the internet (Which I did with no luck). So be nice please.
    1) To replace the chainring, you need to find one that fits. The relevant measurement for a specific crank is called BCD (Bolt circle diameter). Find out how to measure yours here:

    http://www.sheldonbrown.com/gloss_bo-z.html

    2) Once you have found out what BCD cranks you have, tell us which it is so we can tell you whether or not you should even bother replacing it (if it is an obscure or unavailable size) or if you're likely looking at a new crank/bb.

    3) Does your crank have one chainring? 2? 3?

    4) If you really want to keep costs low, why not just run whatever chainring is on the bike currently? How many teeth does it have?
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  5. #5
    cab horn
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    Quote Originally Posted by idiq View Post
    Measure from the center of one bolt on the spider directly to the center of the next bolt on the spider. That will tell you if it's 110 or 130 (metric).
    Gotta love incomplete and misleading directions.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  6. #6
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    Ok, change of plans here. It appears that the spider and chainring are all one unit, so I suppose I'll just get completely new cranks.

    So new question, How do I check what cranks are compatible with my current BB?

    I suppose I should maybe just replace the cranks and BB. Any chance of doing this for less than $80? If so or if not, what specific cranks/BB do you recommend?

    Thanks.

  7. #7
    cab horn
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    Quote Originally Posted by imoprefontaine View Post
    Ok, change of plans here. It appears that the spider and chainring are all one unit, so I suppose I'll just get completely new cranks.

    So new question, How do I check what cranks are compatible with my current BB?

    I suppose I should maybe just replace the cranks and BB. Any chance of doing this for less than $80? If so or if not, what specific cranks/BB do you recommend?

    Thanks.
    FMF/Shimano square taper bb will probably be around that price point. What kind of BB does your current frame take?
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

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