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  1. #1
    mtbr member
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    Jan 2011
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    Seat tube length and flare (NOVA OS MTB)

    I ordered the NOVA OS MTB tubeset for my first bike build.
    http://www.cycle-frames.com/bicycle-...E-BEND-CS.html

    The seat tube is interesting and a bit different from what I used in my frame building class. It is marked as "NOV-CMST-580" and is about 23" long. The marking is on the flared end.

    For this tube, what end is used for the seat cluster and which end is used at the BB joint? Also, what size post should I be using? I am a newbie and somehow hoped that the tubeset would come with a short description page. The website does not seem to describe these aspects of the tubes.

    This tube has a one end that is flared to be larger with a 29.6 OD while the other end is 28.6 OD. The flared section is about 4" long and has a wall thickness of 1.2mm the non flared section has a wall thickness of .9mm.

    A 27.2mm post will almost fit into the flared section. On the non-flared end the ID measures around 26.8 and seems too small.

    My measurements are with a cheap pair of calipers so they are not as accurate as they should be.

    I want to build a size 18" bike so some of the tube needs to be removed. I notice that NOVA allows ordering the tube in different lengths. If needed I can reorder to get a shorter one. I may be calling them to discuss but figured it might be something people on the forum would be willing to help out with as well.

  2. #2
    Moderator Moderator
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    Jan 2004
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    Measure the butts!

    The top is the external butt/flared end. That's where your seatpost will go (and yes, it should fit a 27.2). You will need to measure the butt at the bottom (easy, just hold the tube up to a light and look inside it - you'll see the butting right away).

    My guess is that you need a shorter seat tube, because you don't want to join the thin section (ie, you need at least an inch of butt at the bottom and 2-3" at the top). But I am not familiar enough with that tube to know what the butt lengths are.

    -Walt

    Quote Originally Posted by febikes
    I ordered the NOVA OS MTB tubeset for my first bike build.
    http://www.cycle-frames.com/bicycle-...E-BEND-CS.html

    The seat tube is interesting and a bit different from what I used in my frame building class. It is marked as "NOV-CMST-580" and is about 23" long. The marking is on the flared end.

    For this tube, what end is used for the seat cluster and which end is used at the BB joint? Also, what size post should I be using? I am a newbie and somehow hoped that the tubeset would come with a short description page. The website does not seem to describe these aspects of the tubes.

    This tube has a one end that is flared to be larger with a 29.6 OD while the other end is 28.6 OD. The flared section is about 4" long and has a wall thickness of 1.2mm the non flared section has a wall thickness of .9mm.

    A 27.2mm post will almost fit into the flared section. On the non-flared end the ID measures around 26.8 and seems too small.

    My measurements are with a cheap pair of calipers so they are not as accurate as they should be.

    I want to build a size 18" bike so some of the tube needs to be removed. I notice that NOVA allows ordering the tube in different lengths. If needed I can reorder to get a shorter one. I may be calling them to discuss but figured it might be something people on the forum would be willing to help out with as well.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

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