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Thread: Kid's Bike - Tubing Considerations

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    Default Kid's Bike - Tubing Considerations

    Hi all -

    Currently building a 16" bike for my 4-year-old daughter. Two questions:

    1. I have a pair of 16mm s-bend seatstays that, shape-wise, would work perfect as chainstays on this thing. Any hesitation?

    2. How about nudging some .8 oval chainstays and using them as forkblades?

    Given a <40 lb. rider, any other thoughts on my plan? I wouldn't normally ask this type of question--and would just overbuild whatever I was working on--but I want this bike to be as lightweight and enjoyable as possible, for obvious reasons. So, thanks in advance.

    -Chris


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    Default Re: Kid's Bike - Tubing Considerations

    I've built several small (16" wheel) BMX bikes for kids that young - 3-4 YO. I used 5/8" and 3/4" x .028" chrome moly for seat and chainstays, a 1 1/8" butted seat tube and 1 1/*' and 1 1/4" x .7=.4-.7 top and down tubes. The frames are [plenty stout and came in under 3 pounds. Forks I used 1"x .049" for legs and 1"x .058" for the steer tube,

    A decent 16" BMX wheel is VERY hard to find. By decent I mean sealed bearings, stainless spokes and a good alloy, double-wall rim.

    Your proposed build looks OK to me although the .035" downtube is overkill. You could use 5/8" x .028" for the twin top tubes, same weight and a lot stiffer.

    Good luck!

    jnnonis_bike_1.jpg
     

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    Default Re: Kid's Bike - Tubing Considerations

    Quote Originally Posted by jon_norstog View Post
    ... a 1 1/8" butted seat tube...
    Jon - Thanks for the reply! That's super helpful.

    One quick question: On that little seat tube... I was planning on 1 1/8" .049, to fit a 26.0 post. I had thought about a regular single-butted seat tube with a sleeve (like yours, shown), but I thought the butt taper might get in the way of the post. Is that a 27.2 post just cut extra short? Or did you shim and run a smaller post?

    -Chris

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    Default Re: Kid's Bike - Tubing Considerations

    Quote Originally Posted by cblandford View Post
    Jon - Thanks for the reply! That's super helpful.

    One quick question: On that little seat tube... I was planning on 1 1/8" .049, to fit a 26.0 post. I had thought about a regular single-butted seat tube with a sleeve (like yours, shown), but I thought the butt taper might get in the way of the post. Is that a 27.2 post just cut extra short? Or did you shim and run a smaller post?

    -Chris
    Chris, I used a 28.6 x .9-.6 seat tube. I cut it so I had some of the transition to braze to the bottom bracket, then used a regular 27.2mm seatpost, cut short. I like the looks of the Origin8 'posts that J&B sells and use them as a poor man's Thomson. Kid wont break it and it micro-adjusts. Kids that age range, it's their bodies that are growing and their legs kind of stay the same, so they won't need a taller 'post for a couple years and by then their bodis will be too long to fit in that front cabin. Time for a 20" bike.

    jn
     

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    Default Re: Kid's Bike - Tubing Considerations

    Jon -

    Sweet - thanks! That all makes sense... I appreciate the help. And yes, I'm anticipating undertaking this project a few times in the next decade! Ha. This version only needs to fit a couple years.

    -Chris

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