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  1. #1
    650b me
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    Butted tube selection

    A question for experienced builders: When you've designed a frame, and you're selecting top and down tubes, what is the minimum length of butting required at each end? Is there a general guideline? Thanks.

  2. #2
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    I like to have minimum ~50mm at the head tube end and 25mm at the BB/ST ends (that's from the closest welded point). You could make an argument that you could get away with quite a bit less than that, but if you're that geeked out about weight you probably should get some carbon cloth and resin and forget metal tubes.

    -Walt

    Quote Originally Posted by golden boy View Post
    A question for experienced builders: When you've designed a frame, and you're selecting top and down tubes, what is the minimum length of butting required at each end? Is there a general guideline? Thanks.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  3. #3
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    In another earlier age of inch top tube and 1 1/8" DT, you needed a lot of butt length to keep a frame strong.

    Now that we have choices and Diameter options, the larger tubes (35-42mm) have strength advantages to such a degree that you can shorten butts with no adverse affects.

    The manufacturers are giving us plenty of variations and this is good. Some of the manufacturers give 2 length options so you can better manage a short frame over a long one, design wise and it is your choice which way you can fit it to match your design.

    I agree with Walt, keeping the longer butt at the HT with whatever is left attaching to the BB and ST is standard practice.

    I think your question is relating more to structural integrity than overall weight, so I hope that reasures you.

    Eric
    BRAKES...? I'm trying to go FASTER!!!

  4. #4
    650b me
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    You are correct, Eric. My main concern is safety/strength, not weight. I will err on the side of integrity and get the tube with longer butted sections. Thanks too for the guideline on putting the longer butt at the HT end.

  5. #5
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    Just to clarify which part of the tube to attach to the Head Tube.
    Tubes from Columbus and others have a painted end. You do not cut this end, it is for mitre only. It is the painted end that you fit to the HEAD TUBE.

    Hope that puts everything into correct perspective, was a little absent of mind in my earlier reply. lol. duh.

    Eric
    BRAKES...? I'm trying to go FASTER!!!

  6. #6
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    The painted end isn't always the short end. Double check!

    I always measure the lengths of the butts by looking through the inside of the tube towards a light (this is for the newb), then mark the butt on the outside with a sharpie. I go back to the spec sheet to see if my measurement resembles what they're supposed to be, but I never just go off the spec sheet.

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